CN116657009A - High-strength high-heat-conductivity magnesium alloy and preparation method thereof - Google Patents
High-strength high-heat-conductivity magnesium alloy and preparation method thereof Download PDFInfo
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- CN116657009A CN116657009A CN202210677542.7A CN202210677542A CN116657009A CN 116657009 A CN116657009 A CN 116657009A CN 202210677542 A CN202210677542 A CN 202210677542A CN 116657009 A CN116657009 A CN 116657009A
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- 229910000861 Mg alloy Inorganic materials 0.000 title claims abstract description 240
- 238000002360 preparation method Methods 0.000 title abstract description 11
- 239000011777 magnesium Substances 0.000 claims abstract description 74
- 238000000034 method Methods 0.000 claims abstract description 28
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 239000007787 solid Substances 0.000 claims description 90
- 239000000956 alloy Substances 0.000 claims description 81
- 229910045601 alloy Inorganic materials 0.000 claims description 80
- 239000002002 slurry Substances 0.000 claims description 52
- 239000000463 material Substances 0.000 claims description 37
- 238000010008 shearing Methods 0.000 claims description 36
- 238000001746 injection moulding Methods 0.000 claims description 31
- 230000009974 thixotropic effect Effects 0.000 claims description 31
- 239000002245 particle Substances 0.000 claims description 30
- 238000010438 heat treatment Methods 0.000 claims description 28
- 229910052746 lanthanum Inorganic materials 0.000 claims description 28
- 239000000203 mixture Substances 0.000 claims description 27
- 230000004907 flux Effects 0.000 claims description 23
- 229910052748 manganese Inorganic materials 0.000 claims description 20
- 238000002347 injection Methods 0.000 claims description 17
- 239000007924 injection Substances 0.000 claims description 17
- 238000007670 refining Methods 0.000 claims description 17
- 229910052684 Cerium Inorganic materials 0.000 claims description 14
- 238000003723 Smelting Methods 0.000 claims description 14
- 229910052802 copper Inorganic materials 0.000 claims description 14
- 239000002994 raw material Substances 0.000 claims description 14
- 229910018503 SF6 Inorganic materials 0.000 claims description 12
- SFZCNBIFKDRMGX-UHFFFAOYSA-N sulfur hexafluoride Chemical compound FS(F)(F)(F)(F)F SFZCNBIFKDRMGX-UHFFFAOYSA-N 0.000 claims description 12
- 229960000909 sulfur hexafluoride Drugs 0.000 claims description 12
- 229910052726 zirconium Inorganic materials 0.000 claims description 12
- 239000007790 solid phase Substances 0.000 claims description 7
- 239000000155 melt Substances 0.000 claims description 6
- 238000012545 processing Methods 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 229910001339 C alloy Inorganic materials 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 claims description 2
- 239000002184 metal Substances 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 23
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 230000017525 heat dissipation Effects 0.000 abstract description 5
- 230000008901 benefit Effects 0.000 abstract description 4
- 238000004512 die casting Methods 0.000 description 32
- 239000012071 phase Substances 0.000 description 30
- 238000005728 strengthening Methods 0.000 description 22
- 239000006104 solid solution Substances 0.000 description 17
- 238000005336 cracking Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 12
- 229910052749 magnesium Inorganic materials 0.000 description 11
- 238000005516 engineering process Methods 0.000 description 10
- 230000001681 protective effect Effects 0.000 description 9
- 229910052761 rare earth metal Inorganic materials 0.000 description 9
- 238000013461 design Methods 0.000 description 8
- 229910052725 zinc Inorganic materials 0.000 description 8
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 7
- 238000005266 casting Methods 0.000 description 7
- 238000000465 moulding Methods 0.000 description 7
- 229910052782 aluminium Inorganic materials 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 230000007547 defect Effects 0.000 description 5
- 229910001297 Zn alloy Inorganic materials 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 2
- 229910003808 Sr-Cu Inorganic materials 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000003063 flame retardant Substances 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000003672 processing method Methods 0.000 description 2
- 150000002910 rare earth metals Chemical class 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229910018137 Al-Zn Inorganic materials 0.000 description 1
- 229910018573 Al—Zn Inorganic materials 0.000 description 1
- 229910017985 Cu—Zr Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910007570 Zn-Al Inorganic materials 0.000 description 1
- 229910007565 Zn—Cu Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005429 filling process Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000008204 material by function Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/04—Alloys based on magnesium with zinc or cadmium as the next major constituent
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D17/007—Semi-solid pressure die casting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D17/20—Accessories: Details
- B22D17/32—Controlling equipment
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/03—Making non-ferrous alloys by melting using master alloys
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Powder Metallurgy (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
A high-strength high-heat-conductivity magnesium alloy and a preparation method thereof are provided, wherein the magnesium alloy comprises the following components in percentage by weight: zn:5.0 to 8.0 percent; al:0.5 to 3.0 percent, cu:0.5 to 3.0 percent, zr:0.1 to 1 percent; mn: 0-1%, sr: 0-1%, la:0.5 to 3 percent, ce:0.5 to 3 percent, and the balance of Mg and unavoidable impurities. The invention solves the problem that the existing magnesium alloy can not simultaneously give consideration to high thermal conductivity and high strength; the magnesium alloy has the thermal conductivity of 125-135W/(m.K), the yield strength of 192-216 MPa and the elongation of 7-10%, and can be manufactured into magnesium alloy products with complex structures which cannot be manufactured by a deformation process. The preparation method provided by the invention has the advantages of low cost and convenience for large-scale mass production, and can be widely used for preparing heat dissipation/heat conduction components in the fields of aerospace, 3C products and automobile parts.
Description
Technical Field
The invention relates to the technical field of magnesium alloy material forming, in particular to a high-strength high-heat-conductivity magnesium alloy and a processing method thereof.
Background
Magnesium is the lightest metal material in common engineering applications and has a density of 1.738g/cm 3 About 2/3 of aluminum and 1/4 of steel, and has the advantages of high specific strength, high specific rigidity and other structural materials. Meanwhile, magnesium and magnesium alloy also have the characteristics of functional materials such as high electromagnetic shielding effectiveness, good damping performance, excellent heat conduction performance and the like, and are considered as a structure-function integrated material with great development prospect, so that the magnesium and magnesium alloy are also preferred materials for light weight in the fields of aerospace, rail transit, automobile parts, 3C products and the like.
The thermal conductivity of pure magnesium at room temperature is about 154.5W/(m.K), but the thermal conductivity is obviously reduced when the alloy is used as a structural material through alloying, for example, the thermal conductivities of a common die casting magnesium alloy Mg-9Al-1Zn (AZ 91) and Mg-6Al-0.5Mn (AM 60) are respectively 51.2W/(m.K) and 60.6W/(m.K), and the thermal conductivity coefficient of the alloy is 115W/(m.K) of a commercial brand cast Mg-6Zn-1Zr (ZK 61) magnesium alloy. Meanwhile, the yield strength of the materials is mostly 150-180Mpa, the materials cannot have high mechanical property and high heat conduction property at the same time, and the requirements of high performance of magnesium alloy products cannot be met more and more.
Chinese patent CN109136699B discloses a high heat conduction magnesium alloy, an inverter shell, an inverter and an automobile, and the Mg-Al-Zn-Mn-La-Ce-Nd-Sr-Cu cast magnesium alloy is prepared, wherein the heat conductivity of the alloy is more than 110W/(m.K), but the yield strength is less than 160MPa, and the elongation is 5%. Chinese patent CN111286658A discloses a die-casting high heat conduction flame retardant magnesium alloy and a preparation method thereof, and the die-casting magnesium alloy of Mg-Al-RE-Ca is prepared, wherein the heat conductivity of the alloy is more than 120W/(m.K), and the yield strength is 140-180 MPa. The two alloys have higher heat conduction performance, but the yield strength is not obviously improved compared with commercial brand die-casting AZ91D, chinese patent CN110195180A discloses a high heat conduction die-casting magnesium alloy and a preparation method thereof, and the Mg-Al-La-Sr-Mn die-casting magnesium alloy is prepared, wherein the heat conductivity of the alloy is 108-122W/(m.K), the yield strength is more than 190-210 MPa, and the elongation is more than 6-12%. The alloy has excellent heat conducting performance and mechanical performance, but a large amount of rare earth elements are added, so that the alloy has higher cost.
The magnesium alloy product forming process is divided into two main types, namely deformation and casting, and the deformed magnesium alloy has excellent performance, but the process is complex, the cost is higher, and the magnesium alloy product with complex shape and appearance cannot be prepared. Compared with the deformation process, the casting molding technology such as the die casting technology has the advantages of low manufacturing cost and capability of molding products with complex structures, but the internal porosity of the die casting products is higher, so that the mechanical properties of the products are reduced, and in addition, the die casting process cannot accurately manufacture ultrathin-wall-thickness magnesium alloy products. The semi-solid thixotropic injection molding technology is a molding technology for casting magnesium alloy with potential higher than that of the compression casting technology, and is to stir the magnesium alloy slurry in semi-solid state uniformly and then spray a mold for filling to form the product. Compared with the traditional die-casting magnesium alloy product, the semi-solid thixotropic injection molding magnesium alloy has less internal defects, compact structure, more excellent mechanical property and heat conduction property, and simultaneously can prepare the magnesium alloy product with larger wall thickness range change due to lower linear shrinkage ratio.
Chinese patent CN109136699B discloses a "high heat conductivity magnesium alloy, inverter case, inverter and car", and the Mg-Al-Zn-Mn-La-Ce-Nd-Sr-Cu cast magnesium alloy is prepared by the following chemical components in mass percentage: al:2.0 to 4.0 percent, mn:0.1 to 0.3 percent, la:1.0 to 2.0 percent, ce:2.0 to 4.0 percent, nd:0.1 to 1 percent, zn:0.5 to 2 percent, ca:0.1 to 0.5 percent, sr:0.1 percent, cu is less than or equal to 0.1 percent, and the balance is Mg. The alloy has a thermal conductivity of greater than 110W/(m.K), but a yield strength of less than 160MPa and an elongation of 5%. Although the material has higher heat conductivity, the yield strength is low, and the material can not meet the requirements of high strength and toughness and high heat conductivity of structural materials of a heat dissipation system in the fields of aerospace devices and vehicles.
Chinese patent CN111286658A discloses a "die-casting high heat conduction flame retardant magnesium alloy and preparation method thereof", and the Mg-Al-RE-Ca die-casting magnesium alloy is prepared by the following chemical components in percentage by mass: al:2.5 to 4.5 percent, la or Ce:2.0 to 6.0 percent, sm or Y:0.05 to 0.5 percent, ca:0.01 to 0.45 percent and the balance of Mg. The heat conductivity of the alloy is more than 120W/(m.K), and the yield strength is 140-180 MPa. The alloy has excellent heat conducting performance, but the mechanical performance is not obviously superior to that of the conventional die-casting magnesium alloy AZ91, and a large amount of rare earth elements are added into the alloy, so that the alloy cost is high.
Chinese patent CN110195180A discloses a high-heat-conductivity die-casting magnesium alloy and a preparation method thereof, and the die-casting magnesium alloy is prepared from the following chemical components in percentage by mass: al: 5-7%, la: 5-8%, sr:0.3 to 1 percent, 0.2 to 0.5 percent of Mn, and the balance of Mg and unavoidable impurity elements. The alloy has heat conductivity of 108-122W/(m.K), yield strength of more than 190-210 MPa and elongation of more than 6-12%. The alloy has excellent heat conducting performance and mechanical performance, but a large amount of rare earth elements are added, so that the alloy has higher cost.
In the prior art, the publication AZ91D magnesium alloy semi-solid thixotropic injection structure and process research is carried out to prepare the Mg-Al-Zn semi-solid thixotropic injection molding alloy, wherein the chemical components of the alloy comprise 8.3% of Al by mass, 0.54% of Zn by mass, 0.14% of Mn by mass and the balance of Mg by mass. The alloy has a thermal conductivity of less than 60W/(mK), a yield strength not mentioned and an elongation of about 8%. The alloy cannot simultaneously give consideration to excellent mechanical properties and heat conduction properties, and has limited application fields.
In recent years, the requirements for high-strength and high-heat-conductivity magnesium alloy are more and more urgent, and products such as notebook computer shells, mobile phone shells, automobile central display screen backboard and the like are required to be made of materials with excellent heat-conducting performance and mechanical performance so as to ensure that the products have high working stability and service life. While such products typically have complex configurations, die casting is an ideal choice for cost reasons. However, at present, the heat conductivity of commercial die-casting magnesium alloy such as AZ91D, AM B is less than 70W/(m.K), and the yield strength is less than 160MPa, so that the heat conductivity and the mechanical property cannot be simultaneously considered, and therefore, research on novel magnesium alloy component design and novel forming technology is urgently needed to develop high-strength and high-heat-conductivity magnesium alloy products.
Disclosure of Invention
The invention aims to provide a high-strength high-heat-conductivity magnesium alloy and a preparation method thereof, which solve the problem that the existing magnesium alloy cannot simultaneously achieve high heat conductivity and high strength; the heat conductivity of the magnesium alloy is 125-135W/(m.K), the yield strength is 192-216 MPa, and the elongation is 7-10%; and the magnesium alloy product with complex structure which cannot be manufactured by the deformation process can be manufactured, the process has low cost, is convenient for large-scale mass production, and can be widely used for preparing heat dissipation/heat conduction components in the fields of aerospace, 3C products and automobile parts.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
the high-strength high-heat-conductivity magnesium alloy comprises the following components in percentage by weight: zn:5.0 to 8.0 percent; al:0.5 to 3.0 percent, mn: 0-1%, sr: 0-1%, la:0.5 to 3 percent, ce:0.5 to 3 percent, and the balance of Mg and unavoidable impurities.
The high-strength high-heat-conductivity magnesium alloy comprises the following components in percentage by weight: zn:5.0 to 8.0 percent; cu:0.5 to 3.0 percent, zr:0.1 to 1 percent; mn: 0-1%, sr: 0-1%, la:0.5 to 3 percent, ce:0.5 to 3 percent, and the balance of Mg and unavoidable impurities.
The heat conductivity of the magnesium alloy is 125-135W/(m.K), the yield strength is 192-216 MPa, and the elongation is 7-10%.
In the composition design of the high-strength high-heat-conductivity magnesium alloy, the following components are adopted:
the strengthening mechanism of the mechanical property of the magnesium alloy mainly comprises solid solution strengthening, second phase strengthening and fine grain strengthening, wherein the solid solution strengthening and the second phase strengthening are realized by introducing dissimilar elements into a Mg matrix to improve the mechanical property, however, the introduction of the dissimilar elements can reduce the heat conductivity of the magnesium alloy, and the negative influence of the dissimilar elements on the heat conductivity of the magnesium alloy is far higher than that of the magnesium alloy in the form of the second phase when the dissimilar elements exist in solid solution atoms. In addition, the effect of solid solution of different dissimilar elements in the magnesium alloy matrix on the thermal conductivity is also different.
According to the component design scheme, mg-Zn-Al design is adopted, and a solid solution element Zn with less negative influence on heat conductivity is added, so that the mechanical property of the magnesium alloy is improved in a solid solution strengthening mode; the addition of the Al element can reduce the hot cracking tendency of the semi-solid thixotropic injection molding product, and meanwhile, the Al element forms a second phase with Mn, la, ce and Sr to improve the mechanical property of the magnesium alloy, and the existence form of the second phase obviously reduces the negative influence on the thermal conductivity of the material. By controlling the types and the contents of the alloy elements, the material has the characteristics of high strength and high heat conduction.
Zn element has solid solution strengthening effect in Mg, and has obvious second phase strengthening effect with Mg-Zn second phase formed by Mg, and Zn is also a weak grain refining agent, and can obtain finer microstructure, thereby improving the mechanical property of magnesium alloy. Zn has less negative effect on the heat conductivity of magnesium alloy when it exists in the form of solid solution atoms in Mg. Therefore, the magnesium alloy with high heat conductivity can be developed based on the Mg-Zn system.
In addition, when the Zn content is less than 3%, the heat cracking tendency of the semisolid thixotropic injection molding magnesium alloy is serious, the fluidity of the semisolid slurry is poor, and the mechanical property of the material is poor; excessive Zn element is added to easily form a netlike coarse second phase in the magnesium alloy, so that the toughness and the plasticity of the material are deteriorated, and the heat conducting property of the alloy is reduced. Therefore, the Zn element percentage content is 5-8 percent in the invention.
The Al element has obvious solid solution strengthening effect in Mg, however, the Al element existing in the form of solid solution atoms can obviously reduce the heat conductivity of the magnesium alloy, and the content of each element is controlled to lead the Al element, la, ce, sr and Mn to form Al 11 La 3 、Al 11 Ce 3 、Al 4 Sr and Al 8 Mn 5 Second phases that not only enhance the mechanical properties of the magnesium alloy, but also have less negative impact on thermal conductivity when present as second phases. In addition, the Al element can reduce the two-phase temperature interval of the Mg-Zn alloy, improve the fluidity of the semi-solid slurry and reduce the hot cracking tendency of the magnesium alloy. The content of Al element in the invention is 0.5-3%.
Mn can refine the microstructure of the magnesium alloy and improve the corrosion resistance by controlling the Fe content. In addition, a proper amount of second phase Al formed by Mn and Al 8 Mn 5 Can further improve the strength of the magnesium alloyThe chemical properties. The small amount of Mn has less negative effect on the heat conducting property of the magnesium alloy and reduces the hot cracking tendency of the as-cast magnesium alloy, so that the percentage content of Mn element in the invention is not more than 1 percent.
La and Ce belong to cheap rare earth elements, and can refine magnesium alloy microstructure and purify alloy melt. Rare earth second phase Al, especially with Al 11 La 3 、Al 11 Ce 3 The mechanical property of the magnesium alloy can be obviously improved, and the negative influence of each element on the heat conductivity can be reduced by controlling the formation of a second phase of Al, la and Ce in the magnesium alloy, so that the magnesium alloy is ensured to have excellent heat conductivity and mechanical property. The addition of excessive La and Ce can increase the material cost and reduce the heat conductivity, so that the mass percent of La and Ce in the invention is 0.5-3%.
Small amounts of Sr can significantly refine the grain size of the magnesium alloy, and particularly when Al is contained in the alloy, the formed Al-Sr second phase can play a second phase strengthening role while refining the size of the magnesium alloy. The second phase of Al-Sr causes Al element to exist in the magnesium alloy in the form of the second phase, so that the negative influence of the Al element on the heat conductivity of the magnesium alloy is reduced, and the mass percent of Sr in the invention is not more than 1 percent.
According to the component design scheme II, the Mg-Zn-Cu-Zr design is adopted, and the solid solution element Zn with less negative influence on the heat conductivity is added, so that the mechanical property of the magnesium alloy is improved in a solid solution strengthening mode; the Cu element has less negative influence on the heat conductivity, reduces the hot cracking tendency of the semisolid thixotropic injection molding product, and forms a Mg-Zn-Cu second phase with Mg and Zn to improve the mechanical property of the material; the Zr element can obviously refine grains and improve the mechanical property of the magnesium alloy. By controlling the types and the contents of the alloy elements, the material has the characteristics of high strength and high heat conduction.
Zn element has solid solution strengthening effect in Mg, and has obvious second phase strengthening effect with Mg-Zn second phase formed by Mg, and Zn is also a weak grain refining agent, and can obtain finer microstructure, thereby improving the mechanical property of magnesium alloy. Zn has less negative effect on the heat conductivity of magnesium alloy when it exists in the form of solid solution atoms in Mg. Therefore, the magnesium alloy with high heat conductivity can be developed based on the Mg-Zn system.
In addition, when the Zn content is less than 3%, the heat cracking tendency of the semisolid thixotropic injection molding magnesium alloy is serious, the fluidity of the semisolid slurry is poor, and the mechanical property of the material is poor; excessive Zn element is added to easily form a netlike coarse second phase in the magnesium alloy, so that the toughness and the plasticity of the material are deteriorated, and the heat conducting property of the alloy is reduced. Therefore, the Zn element percentage content is 5-8 percent in the invention.
The Cu element has less negative effect on the heat conductivity when being dissolved in Mg, and can reduce the heat cracking tendency of Mg-Zn alloy and improve the fluidity of semi-solid slurry. In addition, cu, mg and Zn elements form MgZnCu second phase, so that the mechanical property of the magnesium alloy is further improved while the thermal conductivity is ensured. Too much Cu reduces the corrosion resistance of the magnesium alloy, so the Cu content in the invention is 0-3%.
After Zr element is added, the grain size in the Mg-Zn alloy is obviously thinned, the mechanical property of the magnesium alloy is improved in a fine crystal strengthening mode, and the heat conducting property of the magnesium alloy cannot be obviously influenced by a small amount of the added Zr element, so that the mass percentage of Zr in the invention is not more than 1%.
Mn can refine the microstructure of the magnesium alloy and improve the corrosion resistance by controlling the Fe content. The small amount of Mn has less negative effect on the heat conducting property of the magnesium alloy and reduces the hot cracking tendency of the as-cast magnesium alloy, so that the percentage content of Mn element in the invention is not more than 1 percent.
La and Ce belong to cheap rare earth elements, and can refine magnesium alloy microstructure and purify alloy melt. Rare earth second phase Mg formed with Mg 12 La、Mg 12 Ce can obviously improve the mechanical property of the magnesium alloy, and the negative influence of La and Ce on the heat conductivity can be reduced by controlling the formation of a second phase in the magnesium alloy so as to ensure that the magnesium alloy has excellent heat conductivity and mechanical property. The addition of excessive La and Ce can increase the material cost and reduce the heat conductivity, so that the mass percent of La and Ce is 0.5-3 percent in the invention.
The small amount of Sr can obviously refine the grain size of the magnesium alloy, plays a role in fine-grain strengthening to optimize the mechanical property of the magnesium alloy, and has small negative influence on the heat conductivity of the magnesium alloy, so that the mass percentage of Sr in the invention is not more than 1%.
When the Zn content is controlled to be 5-8%, the fluidity of the semi-solid slurry is better, the hot cracking tendency is smaller, meanwhile, the deterioration of the material performance of a coarse netlike Mg-Zn second phase is avoided, the Al element and the Cu element can remarkably improve the fluidity of the semi-solid slurry and reduce the hot cracking tendency, the mechanical performance of the material can be improved by forming the second phase with Al through controlling the La, ce, sr, mn element content, and the negative influence on the heat conductivity is reduced. Zr element obviously refines the grain size of Mg-Zn alloy and improves the mechanical property of the material. The content of each element in Mg is accurately controlled, on the basis of improving the mechanical property of the magnesium alloy, the negative influence of different elements on the heat conduction property of the magnesium alloy is reduced to the greatest extent, meanwhile, the alloy and the semi-solid thixotropic injection molding technology are guaranteed to have good adaptability, the advantage of semi-solid thixotropic injection molding is exerted as much as possible, and finally, the semi-solid thixotropic injection molding magnesium alloy product which takes the heat conduction property and the mechanical property into consideration is prepared.
The invention solves the problem that the existing magnesium alloy cannot simultaneously realize high heat conductivity and high strength without adding a large amount of expensive rare earth elements. The heat conductivity of the magnesium alloy is 125-135W/(m.K), the yield strength is 192-216 MPa, and the elongation is 7-10%; meanwhile, the semi-solid thixotropic injection molding technology is adopted for processing, the product performance is obviously superior to cast magnesium alloy products such as die casting and the like, and the magnesium alloy products with complex structures which cannot be manufactured by a deformation process can be manufactured. The process has low cost, is convenient for large-scale mass production, and can be widely used for preparing heat dissipation/heat conduction components in the fields of aerospace, 3C products and automobile parts.
The invention relates to a preparation method of a high-strength high-heat-conductivity magnesium alloy, which comprises the following steps:
1) Proportioning materials
Taking pure Mg ingot, pure Zn ingot, pure Al ingot, mg-Cu, mg-Zr, mg-Mn, mg-La, mg-Ce and Mg-Sr intermediate alloy as raw materials, and mixing according to the components;
2) Smelting
Putting pure Mg ingot into crucible of smelting furnace, heating to 700-720 deg.C, adding CO 2 And SF (sulfur hexafluoride) 6 The mixture is completely melted to form a melt under the protection of mixed shielding gas, then the temperature is raised to 750-770 ℃, one or more of pure Zn ingot, pure Al ingot, mg-Cu, mg-Zr, mg-Mn, mg-La, mg-Ce and Mg-Sr intermediate alloy are added into the melt in sequence, after the alloy is completely melted, stirring is carried out for 15-20 min, then magnesium alloy flux is added for refining for 10-15 min, surface scum is removed, and finally the temperature is kept for 20-30 min at 720-760 ℃, and magnesium alloy cast ingots are cast;
3) Magnesium alloy particle processing
Placing the magnesium alloy cast ingot into a granulator, and processing into magnesium alloy particles;
4) Semisolid thixotropic injection molding
Placing magnesium alloy particles in a charging barrel of semi-solid thixotropic injection molding equipment, heating to 560-620 ℃ to form magnesium alloy semi-solid slurry, applying shearing force to the semi-solid slurry by utilizing a screw shearing device, and controlling the rotating speed of a screw to be 200-250 r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid metal piece, wherein the injection speed is 2-5 m/s; the temperature of the die is 300-350 ℃; the vacuum degree of the die is 30-100 mbar.
Preferably, in the step 2), the magnesium alloy flux is an RJ-4 flux, an RJ-5 flux or an RJ-6 flux, preferably an RJ-5 flux.
Preferably, in step 3), the particle diameter of the magnesium alloy particles is 0.5 to 1.2mm.
Preferably, in the step 4), the solid phase ratio of the semi-solid slurry is controlled to be 20-60% by volume
The processing method of the high-strength high-heat-conductivity magnesium alloy comprises the following steps:
compared with the existing die-casting magnesium alloy, the semi-solid thixotropic injection molding process is adopted, and the obtained magnesium alloy has high density and low porosity, so that the mechanical property and the heat conducting property of the magnesium alloy are obviously improved, and meanwhile, the magnesium alloy product with more complex shape can be prepared. The semi-solid thixotropic molding technology requires that the alloy semi-solid slurry has enough fluidity to fill a complex mold cavity, and has small hot cracking tendency so as to ensure that the material has a compact microstructure and excellent mechanical properties.
In the semi-solid thixotropic injection molding process, the temperature of the charging barrel is set at 560-620 ℃, the solid phase rate of the semi-solid slurry is set at 20-60%, and the semi-solid slurry has good fluidity under the solid phase rate, and meanwhile, the hot cracking tendency in the alloy filling process is reduced, so that the material has higher mechanical property and heat conducting property. Too high a temperature of the charging barrel leads to too low solid phase rate, poor alloy performance, too high solid phase rate when the temperature of the charging barrel is too low, poor fluidity of semi-solid slurry, and incapability of completely filling the mold. The injection speed is 2-5 m/s, the injection speed is too low, the material cannot be completely filled, the injection speed is too high, the porosity of the material is higher, and the mechanical property and the heat conducting property are reduced.
The rotating speed of the screw is controlled to be 200-250 r/min so as to ensure that the solid phase and the liquid phase in the semi-solid slurry are uniformly distributed.
The temperature of the die is set at 300-350 ℃, and the alloy is complete in filling, so that defects such as cracks and air holes are greatly reduced, and the alloy has excellent performance.
The vacuum degree setting range of the die is 30-100 mbar, defects in the molded product are reduced, and the product performance is improved.
The invention has the beneficial effects that:
according to the high-strength high-heat-conductivity magnesium alloy, conventional alloy elements Zn, al or Cu and Zr are used as basic elements, a small amount of La, ce, mn, sr elements are added, the mechanical properties of the material are improved through solid solution strengthening, second-phase strengthening and fine-grain strengthening, and meanwhile, the magnesium alloy is finally ensured to have higher heat-conductivity by adding solid solution elements Zn and Cu which have less damage to the heat conductivity of the magnesium alloy or precisely controlling the proportion of alloy elements Al, la, ce, mn, sr to exist in a second-phase form in the magnesium matrix; in addition, the material cost is reduced as much as possible on the premise of adding a small amount of cheap rare earth elements La and Ce to ensure the performance. The magnesium alloy obtained by the invention has high thermal conductivity and high mechanical property, and the heat conductivity coefficient of the magnesium alloy is more than or equal to 125W/(m.K), the yield strength is more than or equal to 190MPa, and the elongation is more than or equal to 7%.
According to the invention, the content of Zn, al and Cu elements is controlled in component design, sr, zr, mn, la, ce and other elements are selected to be added for multi-element alloying, so that the semi-solid slurry of the alloy has good fluidity on the basis of ensuring high mechanical property and heat conduction property of the magnesium alloy, and the complex mold cavity can be filled when the semi-solid thixotropic injection molding process is adopted for molding, so that a magnesium alloy product with a complex structure is manufactured, and meanwhile, the prepared magnesium alloy product has fewer defects such as material pores, thermal cracks and the like, and can be used for manufacturing complex structural members of heat dissipation/heat conduction systems of aerospace electronic devices, 3C products, vehicles and the like.
The invention adopts semi-solid thixotropic injection molding technology, and by controlling the temperature of the charging barrel, the injection speed, the stirring speed, the mold temperature and the mold vacuum degree, the defects of pores, cracks and the like in the material are reduced while the good fluidity of semi-solid slurry is ensured, and the magnesium alloy product with excellent performance is manufactured, and the performance is superior to the cast magnesium alloy of the traditional die casting and the like, and the process cost is low, thereby being convenient for large-scale mass production.
Detailed Description
The technical scheme of the present invention is described in detail below by examples, which are given as detailed embodiments and specific operation procedures on the premise of the technical scheme of the present invention, but the scope of protection of the present invention is not limited to the examples below.
The magnesium alloy composition of the present example is shown in table 1, and the balance contains Mg and unavoidable impurities. The preparation process parameters of the examples are shown in Table 2, and Table 3 shows the performance parameters of the magnesium alloys of the examples.
Example 1
1) The components of the high-strength high-heat-conductivity magnesium alloy are designed and selected as follows: 5.2wt% of Zn,0.5wt% of Al,1.0wt% of Sr,0.5wt% of La,0.5wt% of Ce and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, pure Al ingots, mg-Sr, mg-La and Mg-Ce intermediate alloy are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into crucible of smelting furnace, heating to 705 deg.C, adding CO 2 And SF (sulfur hexafluoride) 6 Is mixed with the protective gasAfter the alloy is completely melted, adding RJ-6 flux into the melted melt for refining for 15min, removing surface scum, and finally preserving heat for 20min at 750 ℃ to cast a magnesium alloy cast ingot;
3) Placing the magnesium alloy cast ingot in a granulator, and processing magnesium alloy particles with the size of 0.5mm multiplied by 1mm multiplied by 6 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 570 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 230r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 2m/s; the temperature of the die is 300 ℃; the mold vacuum was 55mbar.
Example 2
1) The components of the high-plasticity heat-conducting magnesium alloy are designed and selected as follows: 7.9wt% of Zn,2.5wt% of Al,0.3wt% of Mn,0.7wt% of Sr,1.5wt% of La,1.6wt% of Ce and the balance of Mg, and the magnesium alloy is prepared by taking pure Mg ingots, pure Zn ingots, pure Al ingots, mg-Mn, mg-Sr, mg-La and Mg-Ce intermediate alloy as raw materials according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into crucible of smelting furnace, heating to 715 deg.C, adding CO 2 And SF (sulfur hexafluoride) 6 The mixture is completely melted under the protection of the mixed shielding gas, then the temperature is raised to 770 ℃, the pure Zn ingot, the pure Al ingot, the Mg-Mn, the Mg-Sr, the Mg-La and the Mg-Ce intermediate alloy are added into the melted melt, after the alloy is completely melted, the mixture is fully stirred for 18min, the RJ-4 flux is added for refining for 13min, the surface scum is removed, and finally the mixture is kept at 755 ℃ for 25min, and then the magnesium alloy ingot is cast;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 0.8mm multiplied by 0.9mm multiplied by 5.1 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 565 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 250r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 4.3m/s; the temperature of the die is 330 ℃; the mould vacuum was 85mbar.
Example 3
1) The components of the high-strength high-heat-conductivity magnesium alloy are designed and selected as follows: 6wt% of Zn,1.5wt% of Al,1.0wt% of Mn,0.5wt% of Sr,1.1wt% of La,0.9wt% of Ce and the balance of Mg, and the magnesium alloy is prepared by taking pure Mg ingots, pure Zn ingots, pure Al ingots, mg-Mn, mg-Sr, mg-La and Mg-Ce intermediate alloy as raw materials according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 706 ℃, and adding CO 2 And SF (sulfur hexafluoride) 6 The mixed protective gas is completely melted under the protection of the mixed protective gas, then the temperature is raised to 765 ℃, pure Zn ingot, pure Al ingot, mg-Mn, mg-Sr, mg-La and Mg-Ce intermediate alloy are sequentially added into the melted melt, after the alloy is completely melted, the mixture is fully stirred for 15min, RJ-6 flux is added for refining for 12min, the surface scum is removed, and finally, the mixture is kept at 750 ℃ for 22min, and then the magnesium alloy ingot is cast;
3) Placing a magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 0.7mm multiplied by 1.2mm multiplied by 6 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 605 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 245r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 5m/s; the temperature of the die is 310 ℃; the mold vacuum was 60mbar.
Example 4
1) The components of the high-strength high-heat-conductivity magnesium alloy are designed and selected as follows: 7.1wt% of Zn,2.9wt% of Al,0.2wt% of Mn,0.3wt% of Sr,2wt% of La,1.2wt% of Ce and the balance of Mg, and the magnesium alloy is prepared by taking pure Mg ingots, pure Zn ingots, pure Al ingots, mg-Mn, mg-Sr, mg-La and Mg-Ce intermediate alloy as raw materials according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 708 ℃, and heating to CO 2 And SF (sulfur hexafluoride) 6 The mixture is completely melted under the protection of the mixed shielding gas, then the temperature is raised to 770 ℃, the pure Zn ingot, the pure Al ingot, the Mg-Mn, the Mg-Sr, the Mg-La and the Mg-Ce intermediate alloy are sequentially added into the melted melt, after the alloy is completely melted, the mixture is fully stirred for 16min, the RJ-6 flux is added for refining for 15min, the surface scum is removed, and finally the mixture is preserved for 23min at 745 ℃, and then the magnesium alloy cast ingot is cast;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 1.2mm multiplied by 4.5 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 590 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 200r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 3.1m/s; the temperature of the die is 307 ℃; the mould vacuum was 100mbar.
Example 5
1) The components of the high-strength high-heat-conductivity magnesium alloy are designed and selected as follows: 5.0wt% of Zn,2.1wt% of Al,0.5wt% of Mn,0.1wt% of Sr,2.9wt% of La,0.8wt% of Ce and the balance of Mg, and the magnesium alloy is prepared by taking pure Mg ingots, pure Zn ingots, pure Al ingots, mg-Mn, mg-Sr, mg-La and Mg-Ce intermediate alloy as raw materials according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into crucible of smelting furnace, heating to 700 deg.C, heating to CO 2 And SF (sulfur hexafluoride) 6 The mixed protective gas is completely melted under the protection of the mixed protective gas, then the temperature is raised to 750 ℃, the pure Zn ingot, the pure Al ingot, the Mg-Mn, the Mg-Sr, the Mg-La and the Mg-Ce intermediate alloy are sequentially added into the melted melt, after the alloy is completely melted, the mixture is fully stirred for 16min, the RJ-5 flux is added for refining for 12min, the surface scum is removed, and finally the mixture is preserved for 30min at 730 ℃ and is cast into magnesium alloy ingots;
3) Placing a magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 0.7mm multiplied by 1.2mm multiplied by 5 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 620 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 205r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 4.5m/s; the temperature of the die is 335 ℃; the mould vacuum was 95mbar.
Example 6
1) The components of the high-strength high-heat-conductivity magnesium alloy are designed and selected as follows: 6.3wt% of Zn,3wt% of Al,0.9wt% of Mn,0.9wt% of La,2.5wt% of Ce and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, pure Al ingots, mg-Mn, mg-La and Mg-Ce intermediate alloys are used as raw materials, and the ingredients are proportioned according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into crucible of smelting furnace, heating to 705 deg.C, adding CO 2 And SF (sulfur hexafluoride) 6 The mixed protective gas is completely melted under the protection of the mixed protective gas, then the temperature is raised to 755 ℃, the pure Zn ingot, the pure Al ingot, the Mg-Mn, the Mg-Sr, the Mg-La and the Mg-Ce intermediate alloy are sequentially added into the melted melt, after the alloy is completely melted, the mixture is fully stirred for 18min, the RJ-5 flux is added for refining for 11min, the surface scum is removed, and finally the mixture is preserved for 20min at 740 ℃ to be cast into magnesium alloy ingots;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 0.9mm multiplied by 5.5 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 585 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 220r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 2.5m/s; the temperature of the die is 305 ℃; the mould vacuum was 30mbar.
Example 7
1) The components of the high-strength high-heat-conductivity magnesium alloy are designed and selected as follows: 5.1wt% of Zn,1wt% of Cu,0.3wt% of Zr,0.6wt% of Mn,0.6wt% of La,1.5wt% of Ce and the balance of Mg, and the magnesium alloy is prepared by taking pure Mg ingots, pure Zn ingots, mg-Cu, mg-Zr, mg-Mn, mg-La and Mg-Ce intermediate alloy as raw materials according to the designed weight percentage of the magnesium alloy components;
2) Pure Mg ingot is put into a smelting furnaceHeating to 720 ℃ in the crucible of CO 2 And SF (sulfur hexafluoride) 6 The mixture is completely melted under the protection of the mixed shielding gas, then the temperature is raised to 760 ℃, the pure Zn ingot, the pure Al ingot, the Mg-Zr, the Mg-Mn, the Mg-Sr, the Mg-La and the Mg-Ce intermediate alloy are sequentially added into the melted melt, after the alloy is completely melted, the mixture is fully stirred for 15min, the RJ-5 flux is added for refining for 15min, the surface scum is removed, and finally the mixture is preserved for 25min at 730 ℃ to be cast into magnesium alloy ingots;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 0.5mm multiplied by 1.1mm multiplied by 5.2 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 600 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 210r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 3.8m/s; the temperature of the die is 320 ℃; the mould vacuum was 35mbar.
Example 8
1) The components of the high-plasticity heat-conducting magnesium alloy are designed and selected as follows: 6.2wt% of Zn,2wt% of Cu,0.6wt% of Zr,0.1wt% of Mn,0.8wt% of Sr,0.7wt% of La,0.6wt% of Ce and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, mg-Cu, mg-Zr, mg-Sr, mg-La and Mg-Ce intermediate alloys are used as raw materials, and the designed weight percentages of the magnesium alloy components are proportioned;
2) Putting pure Mg ingot into crucible of smelting furnace, heating to 700 deg.C, heating to CO 2 And SF (sulfur hexafluoride) 6 The mixed protective gas is completely melted under the protection of the mixed protective gas, then the temperature is raised to 755 ℃, the pure Zn ingot, mg-Cu, mg-Zr, mg-Sr, mg-La and Mg-Ce intermediate alloy are sequentially added into the melted melt, after the alloy is completely melted, the mixture is fully stirred for 20min, RJ-5 flux is added for refining for 15min, the surface scum is removed, and finally the mixture is kept at 750 ℃ for 25min, and then the magnesium alloy ingot is cast;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 0.7mm multiplied by 0.8mm multiplied by 6 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 610 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 246r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 4.2m/s; the temperature of the die is 350 ℃; the mould vacuum was 90mbar.
Example 9
1) The components of the high-plasticity heat-conducting magnesium alloy are designed and selected as follows: 8wt% of Zn,3.0wt% of Cu,1.0wt% of Zr,0.6wt% of Sr,1.2wt% of La,0.7wt% of Ce and the balance of Mg, and the magnesium alloy is prepared by taking pure Mg ingots, pure Zn ingots, mg-Cu, mg-Zr, mg-Sr, mg-La and Mg-Ce intermediate alloy as raw materials according to the designed weight percentage of the magnesium alloy components;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 710 ℃, and adding CO 2 And SF (sulfur hexafluoride) 6 The mixture is completely melted under the protection of the mixed shielding gas, then the temperature is raised to 760 ℃, pure Zn ingot, mg-Cu, mg-Zr, mg-Mn, mg-Sr, mg-La and Mg-Ce intermediate alloy are sequentially added into the melted melt, after the alloy is completely melted, the mixture is fully stirred for 20min, RJ-5 flux is added for refining for 11min, surface scum is removed, finally the temperature is kept at 760 ℃ for 25min, and a magnesium alloy cast ingot is formed by casting;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 0.9mm multiplied by 1.0mm multiplied by 4.1 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 560 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the rotating speed of a screw is 215r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 4.9m/s; the temperature of the die is 325 ℃; the mould vacuum was 75mbar.
Example 10
1) The components of the high-plasticity heat-conducting magnesium alloy are designed and selected as follows: 6.9wt% of Zn,0.5wt% of Cu,0.7wt% of Zr,0.8wt% of Mn,0.2wt% of Sr,1wt% of La,2wt% of Ce and the balance of Mg, wherein pure Mg ingots, pure Zn ingots, mg-Cu, mg-Zr, mg-Mn, mg-Sr, mg-La and Mg-Ce intermediate alloys are used as raw materials, and the designed weight percentages of the magnesium alloy components are proportioned;
2) Putting pure Mg ingot into a crucible of a smelting furnace, heating to 720 ℃, and adding CO 2 And SF (sulfur hexafluoride) 6 The mixture is completely melted under the protection of the mixed shielding gas, then the temperature is raised to 750 ℃, pure Zn ingot, mg-Cu, mg-Zr, mg-Mn, mg-Sr, mg-La and Mg-Ce intermediate alloy are sequentially added into the melted melt, after the alloy is completely melted, the mixture is fully stirred for 17min, RJ-5 flux is added for refining for 13min, surface scum is removed, and finally the mixture is kept at 725 ℃ for 28min, and then a magnesium alloy cast ingot is formed by casting;
3) Placing the magnesium alloy cast ingot in a granulator to process magnesium alloy particles with the size of 0.7mm multiplied by 1.2mm multiplied by 5.8 mm;
4) Placing magnesium alloy particles into a charging barrel of semi-solid thixotropic injection molding equipment, heating to 595 ℃ to form semi-solid slurry, and simultaneously applying shearing force to the semi-solid slurry by using a screw shearing device, wherein the screw rotating speed is 240r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid piece, wherein the injection speed is 4.1m/s; the temperature of the die is 340 ℃; the mould vacuum was 40mbar.
Comparative example 1
The magnesium alloy comprises the following components in percentage by weight: 9wt% of Al,1wt% of Zn and the balance of Mg;
the alloy is designed and proportioned according to the mass percentages of the elements by taking pure Mg ingots, pure Al ingots and pure Zn ingots as raw materials. In CO 2 +SF 6 Adding pure Mg ingot into a crucible furnace under gas protection, heating to 725 ℃ until the pure Mg ingot is completely melted, sequentially adding pure Al ingot and pure Zn ingot after the temperature is increased to 750 ℃, fully stirring for 12 minutes after the alloy is completely melted, adding RJ-5 flux for refining for 16 minutes, removing surface scum, preserving heat at 750 ℃ for 20 minutes, and transferring to a die casting machine heat preserving furnace; and (3) die casting on a magnesium alloy die casting machine, wherein the melt temperature is 650 ℃, and the die temperature is 300 ℃ to obtain an AZ91D die casting.
Comparative example 2
The magnesium alloy comprises the following components in percentage by weight: 6wt% Al,0.5wt% Mn, the balance Mg;
taking pure Mg ingot, pure Al ingot and Mg-Mn intermediate alloy as raw materials according to the mass percentages of the elementsThe alloy is designed and proportioned according to the number. In CO 2 +SF 6 Adding pure Mg ingot into a gas-shielded crucible furnace, heating to 725 ℃ until the pure Mg ingot is completely melted, sequentially adding pure Al ingot and Mg-Mn intermediate alloy after the temperature is raised to 760 ℃, fully stirring for 15 minutes after the alloy is completely melted, adding RJ-5 for refining for 18 minutes, removing surface scum, preserving heat at 750 ℃ and standing for 20 minutes, and finally casting into magnesium alloy ingots. Transferring to a die casting machine heat preservation furnace; and (3) die casting on a magnesium alloy die casting machine, wherein the temperature of a melt is 660 ℃, and the temperature of a die is 290 ℃ to obtain an AM60B die casting.
The comparative examples 1 and 2 were made by using commercial grades AZ91D and AM60, respectively, and the molding process of these two grades was a conventional die casting process. The invention adopts the design principle of high-strength high-heat-conductivity magnesium alloy, and the molding process is a semi-solid injection molding process.
As is clear from Table 3, the thermal conductivity of the magnesium alloy of the present invention is not less than 125W/(mK), and the yield strength is not less than 190MPa.
Compared with the traditional AZ91D magnesium alloy and AM60B magnesium alloy, the magnesium alloy obtained by the invention has obviously improved yield strength and tensile strength and obviously improved heat conductivity.
The traditional die-casting AZ91D magnesium alloy and the die-casting AM60B magnesium alloy take Al as main alloy elements, play roles of solid solution strengthening and second phase (Mg 17Al 12) strengthening to improve the strength of the material, and simultaneously, add a small amount of Zn and Mn to further improve the comprehensive mechanical property of the material; however, this strengthening effect is limited, and Al element significantly reduces the thermal conductivity of the material when it is solid-dissolved in magnesium base.
In addition, the die-casting magnesium alloy has lower comprehensive mechanical property due to higher porosity and lower density. As can be seen from the comparative examples in Table 3, the die cast AZ91D magnesium alloy and the die cast AM60B magnesium alloy have thermal conductivities of less than 65W/(m.K) and yield strengths of less than 155MPa.
Table 1 alloy chemical composition unit: weight percent%
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Table 2 semi-solid injection molding process parameters
TABLE 3 mechanical and thermal properties of alloys
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Claims (7)
1. The high-strength high-heat-conductivity magnesium alloy comprises the following components in percentage by weight: zn:5.0 to 8.0 percent; al:0.5 to 3.0 percent, mn: 0-1%, sr: 0-1%, la:0.5 to 3 percent, ce:0.5 to 3 percent, and the balance of Mg and unavoidable impurities.
2. The high-strength high-heat-conductivity magnesium alloy comprises the following components in percentage by weight: zn:5.0 to 8.0 percent; cu:0.5 to 3.0 percent, zr:0.1 to 1 percent; mn: 0-1%, sr: 0-1%, la:0.5 to 3 percent, ce:0.5 to 3 percent, and the balance of Mg and unavoidable impurities.
3. The high-strength and high-heat-conductivity magnesium alloy according to claim 1 or 2, wherein the magnesium alloy has a thermal conductivity of 125 to 135W/(m-K), a yield strength of 192 to 216MPa, and an elongation of 7 to 10%.
4. The method for preparing the high-strength and high-heat-conductivity magnesium alloy according to claim 1, 2 or 3, comprising the following steps:
1) Proportioning materials
Taking pure Mg ingot, pure Zn ingot, pure Al ingot, mg-Cu, mg-Zr, mg-Mn, mg-La, mg-Ce and Mg-Sr intermediate alloy as raw materials, and preparing materials according to the components of claim 1 or 2;
2) Smelting
Putting pure Mg ingot into crucible of smelting furnace, heating to 700-720 deg.C, adding CO 2 And SF (sulfur hexafluoride) 6 The mixture is completely melted to form a melt under the protection of mixed shielding gas, then the temperature is raised to 750-770 ℃, one or more of pure Zn ingot, pure Al ingot, mg-Cu, mg-Zr, mg-Mn, mg-La, mg-Ce and Mg-Sr intermediate alloy are added into the melt in sequence, after the alloy is completely melted, stirring is carried out for 15-20 min, then magnesium alloy flux is added for refining for 10-15 min, heat preservation is carried out for 20-30 min at 720-760 ℃, and magnesium alloy cast ingot is cast;
3) Magnesium alloy particle processing
Placing the magnesium alloy cast ingot into a granulator, and processing into magnesium alloy particles;
4) Semisolid thixotropic injection molding
Placing magnesium alloy particles in a charging barrel of semi-solid thixotropic injection molding equipment, heating to 560-620 ℃ to form magnesium alloy semi-solid slurry, applying shearing force to the semi-solid slurry by utilizing a screw shearing device, and controlling the rotating speed of a screw to be 200-250 r/min; after shearing is finished, injecting the magnesium alloy semi-solid slurry into a mould to form a semi-solid metal piece, wherein the injection speed is 2-5 m/s; the temperature of the die is 300-350 ℃; the vacuum degree of the die is 30-100 mbar.
5. The method for preparing a high-strength and high-heat-conductivity magnesium alloy according to claim 4, wherein in the step 2), the magnesium alloy flux is RJ-4 flux, RJ-5 flux or RJ-6 flux, preferably RJ-5 flux.
6. The method of producing a high-strength and high-heat-conductivity magnesium alloy according to claim 4, wherein in step 3), said magnesium alloy particles have a particle diameter of 0.5 to 1.2mm.
7. The method for preparing a high-strength and high-heat-conductivity magnesium alloy according to claim 4, wherein in the step 4), the solid phase ratio of the semi-solid slurry is controlled to be 20-60% by volume.
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|---|---|---|---|---|
| JPH0533096A (en) * | 1991-07-26 | 1993-02-09 | Toyota Motor Corp | Heat resistant magnesium alloy |
| JPH07216489A (en) * | 1994-01-28 | 1995-08-15 | Ube Ind Ltd | Magnesium alloy for casting |
| CN1265007C (en) * | 2003-06-18 | 2006-07-19 | 北京有色金属研究总院 | Mg-Zn-Al based magnesium alloy and its smelting method |
| CN101497129A (en) * | 2009-02-25 | 2009-08-05 | 长春工业大学 | Semi-solid-state injection molding method of magnesium alloy |
| KR101007856B1 (en) * | 2009-12-14 | 2011-01-14 | 한국기계연구원 | High strength and high ductility magnesium alloy |
| CN102433478B (en) * | 2011-12-28 | 2013-11-06 | 东北大学 | Magnesium alloy with good millability and preparation method of magnesium alloy plate |
| CN102392165B (en) * | 2011-12-28 | 2013-04-10 | 东北大学 | Wrought magnesium alloy with high intensity and method for preparing its extruded material |
-
2022
- 2022-06-15 CN CN202210677542.7A patent/CN116657009A/en active Pending
-
2023
- 2023-02-16 WO PCT/CN2023/076351 patent/WO2023241077A1/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117778846A (en) * | 2023-12-25 | 2024-03-29 | 鞍钢股份有限公司 | High-surface-quality rare earth magnesium alloy bar and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2023241077A1 (en) | 2023-12-21 |
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