CN109868402B - High-strength-toughness heat-resistant die-casting Mg-Y alloy and preparation method thereof - Google Patents

High-strength-toughness heat-resistant die-casting Mg-Y alloy and preparation method thereof Download PDF

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CN109868402B
CN109868402B CN201910250020.7A CN201910250020A CN109868402B CN 109868402 B CN109868402 B CN 109868402B CN 201910250020 A CN201910250020 A CN 201910250020A CN 109868402 B CN109868402 B CN 109868402B
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叶兵
刘子利
丁文江
蒋海燕
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Shanghai Jiaotong University
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Abstract

The invention provides a high-strength and high-toughness heat-resistant die-casting Mg-Y alloy and a pressure casting preparation method thereof, wherein the alloy comprises the following elements in percentage by mass: 2.5-5.0% of Y, 1.0-4.0% of Zn, 0.5-1.2% of Al, 0.1-0.3% of Mn, 0.01-0.08% of M, and the balance of Mg and other inevitable impurities; wherein M is Ti and B is at least one element. After the high-strength high-toughness heat-resistant die-casting Mg-Y alloy is subjected to pressure casting, the room-temperature tensile strength of the die-casting state alloy reaches 315MPa, the high-temperature tensile strength at 200 ℃ reaches 210MPa, the room-temperature elongation reaches 12.0%, the die-casting state alloy can be used without aging or solution heat treatment, and the high-end requirement of industries such as aerospace, automobiles, telecommunication and the like on light weight development is met.

Description

High-strength-toughness heat-resistant die-casting Mg-Y alloy and preparation method thereof
Technical Field
The invention relates to a high-strength and high-toughness heat-resistant die-casting Mg-Y alloy and a preparation method thereof, belonging to the field of industrial magnesium alloys and manufacturing thereof.
Background
The magnesium alloy is used as the lightest engineering metal material (the density of magnesium is 2/3 of aluminum and 1/4 of steel), the specific strength of the magnesium alloy is obviously higher than that of aluminum alloy and steel, the specific stiffness of the magnesium alloy is equivalent to that of the aluminum alloy and the steel but far higher than that of engineering plastics, and the magnesium alloy has a series of advantages of good castability, good cutting processability, good thermal conductivity, strong damping property and electromagnetic shielding capability, easy recovery and the like, and has wide application prospects in the fields of aviation, aerospace, automobiles, electronics, national defense war industry and the like. Magnesium alloys have become ideal materials to replace aluminum alloys, steel and engineering plastics to achieve light weight, with the most promising replacement potential being aluminum alloys.
Pressure casting is a casting method in which liquid or semi-solid metal is filled into a die-casting mold cavity at high speed under the action of high pressure and is solidified under pressure to form a casting. The die casting not only ensures that the casting has higher strength, dimensional accuracy and surface smoothness, but also is easy to realize mechanization and automation, has high production efficiency, and can produce thin-wall castings with complex shapes, thereby being widely applied to industries of automobiles, electronic instruments, telecommunication and the like.
Magnesium alloy die casting is the most competitive of all casting methods, and it is even lower in production cost than aluminum alloy die casting. The reason is that (1) the magnesium alloy has lower volume specific heat and thermal conductivity, the die casting has high productivity, the thermal shock of the alloy liquid to the die is small, and the service life of the die is long; (2) magnesium does not react with iron, the die sticking tendency is small, and the die filling speed is higher under the same die filling pressure, so that the smaller die drawing slope ensures that the casting with more complex appearance and higher tolerance precision can be produced. In recent years, the use of magnesium alloy die casting in the automobile and telecommunications industries has been rapidly increased due to the increased environmental pressure and the demand for lightweight and energy saving, and has accounted for the second place of magnesium consumption, of which 80% is used in the automobile industry.
AZ (such as AZ91) and AM series magnesium alloy (such as AM60 and AM50) are the most widely applied commercial die-casting magnesium alloy at present and are widely applied to automobile and 3C product die castings. AZ91D has excellent casting performance, can cast thin-wall die castings with precise and complex structures, but has poor plasticity, the elongation is only 3 percent, the plasticity of AM60 is good, the elongation reaches 8 percent, the product is commonly used for manufacturing shock-absorbing and impact-resistant automobile safety parts such as instrument panel supports, seat frames and the like, but has low strength and yield strength of only 130 MPa. In addition, AZ and AM series magnesium alloys have poor high temperature creep properties and rapidly decrease in tensile strength at temperatures above 150 ℃ due to the supersaturated alpha-Mg matrix Mg at grain boundaries during high temperature creep17Al12The phases are separated out discontinuously. Mg-Al-RE die-cast magnesium alloy is developed on the basis of improving the heat resistance of Mg-Al alloy by adding alloy elements to improve the characteristics (crystal structure, form and thermal stability) of precipitated phases. The commercial magnesium alloy AE44 with the best comprehensive mechanical property developed by the Dow chemical company in the United states at present has typical properties of yield strength of 140MPa, tensile strength of 247MPa and elongation of 11%. Although the AE magnesium alloy has relatively excellent elongation, the normal temperature and high temperature mechanical properties of the AE magnesium alloy can not reach the level of A380 die casting aluminum alloy which is widely applied at present, and the AE magnesium alloy is difficult to produce due to the die sticking tendency during die casting, thereby severely limiting the application development of the AE magnesium alloy.
Zn is an important alloy element in magnesium alloy, the maximum solid solubility in Mg is as high as 6.2 wt%, and the Zn can play a role in solid solution strengthening and aging strengthening. Typical Mg-Zn-based cast magnesium alloys include ZK51A and ZK60A, and wrought alloys include ZK21A, ZK31, ZK40A, ZK60A, and ZK61, and the like. As the Zn content increases, the tensile strength and yield strength of the alloy increase, but the elongation after fracture thereof decreases, and the castability, process plasticity and weldability deteriorate, particularly the tendency to hot crack is extremely severe due to the excessively wide solidification range (for example, the solidification range of ZK60 is as high as 265 ℃, Journal of Materials Science 45(14) (2010)3797- > 3803.) and thus cannot be used for die casting.
The beneficial effect of rare earth elements on the strength performance of magnesium alloy and the grain refinement effect of zirconium on the magnesium alloy are discovered in the thirties of the twentieth century, and EK31 in Mg-RE-Zr series (EK30, EK31 and EK41) becomes the earliest successfully developed high-temperature cast magnesium alloy in Mg-Zr series. Magnesium rare earth alloys based on rare earth RE elements have excellent age hardening effect, and various novel magnesium alloys taking RE as a main element, such as WE54 and WE43 alloys of Mg-Y series, are developed in sequence. Chinese invention patent 201410564817.1 (high thermal conductivity die-casting Mg-Y-Zr series multi-element magnesium alloy and preparation method thereof) reports a high thermal conductivity die-casting corrosion-resistant magnesium alloy, the component content of the magnesium alloy is that the content of Y is 1.5-4 wt.%, the content of Mn is 0.001-1 wt.%, the content of Zn is 0.001-2 wt.%, the content of Ca is 0.001-1 wt.%, the content of Zr is 0.4-0.8 wt.%, and the rest is Mg; the addition of Ca element in the alloy sharply increases the solidification temperature range of the alloy, increases the hot cracking tendency, and the tensile strength of the die-casting ingot is only 140-190 MPa.
The Mg-Y alloy is added with cheap Zn, which not only has more remarkable effect on regulating and controlling aging precipitation structure, but also can form a plurality of strengthening phases under different Zn/Y ratio conditions: when the Zn/Y mass ratio in the alloy is more than or equal to 4.13 (the atomic ratio is more than or equal to 6.0), an icosahedral quasicrystal structure I phase (Mg) is easily formed3Zn6Y); when the mass ratio of Zn to Y in the alloy is between 1.10 and 4.13 (the atomic ratio is between 1.5 and 6.0), a W phase (Mg) with a face-centered cubic structure is easy to form3Zn3Y2) And phase I; when the mass ratio of Zn to Y in the alloy is between 0.69 and 1.10 (the atomic ratio is between 1.0 and 1.5), W phase and long-period stacking ordered structure LPSO phase (Mg) are easily formed12ZnY); when the mass ratio of Zn to Y in the alloy is less than or equal to 0.69 (the atomic ratio is less than or equal to 1.0)LPSO phases (Materials Letter, 59(29) (2005) 3801-. The room temperature strength and the high temperature performance of the magnesium alloy can be further improved by various Mg-Y-Zn strengthening phases, and the quasi-crystal reinforced magnesium alloy reported in Chinese patent invention 200910219870.7 (a quasi-crystal reinforced magnesium alloy and a semi-solid preparation method thereof) comprises the following components in percentage by mass: 4-15% of Zn, 0.5-3.5% of Y, 3-10% of Al and the balance of Mg; the preparation method of the alloy comprises the steps of extruding the Mg-Zn-Y-Al alloy cast ingot into a bar by a hot extrusion method, heating the extruded bar to be in a semi-solid state by an electromagnetic induction heating device, and carrying out semi-solid die-casting molding. The invention discloses a self-generated quasicrystal reinforced Mg-Zn-Y alloy reported by Chinese patent ZL201110155378.5 (a self-generated quasicrystal reinforced Mg-Zn-Y alloy and a smelting method thereof), which comprises the following chemical components in percentage by mass: 3.0-10.0% of Zn, 0.5-3.0% of Y, 0.05-1.0% of Al-Ti-C and the balance of Mg and inevitable impurities; the preparation method comprises smelting and casting, wherein when the temperature of a smelted melt is reduced to 700-720 ℃, Al-Ti-C intermediate alloy is added, ultrasonic waves are introduced into the melt, and the melt is cast after ultrasonic treatment; the tensile strength of the self-generated quasicrystal reinforced Mg-Zn-Y alloy can reach 260MPa, and the elongation is 10.6%. The technology of the invention still has the following problems: the alloy has the advantages that the Zn/Y mass ratio content is too high, the quasicrystal I phase is formed, the solidification interval is too large, only gravity casting can be performed but die casting is not suitable, ultrasonic treatment is introduced, the operation is too complicated, and large-scale industrial application is difficult. Under the conventional solidification condition, the Mg-Y-Zn alloy has coarse grains, the precipitated phase is often in a coarse network structure, the mechanical property of the Mg-Y-Zn alloy is deteriorated, the size of the precipitated phase must be adjusted through thermal deformation or heat treatment solid solution and aging so as to play a role of a strengthening phase of the Mg-Y-Zn alloy, the existing Mg-Y-Zn alloy is generally limited to gravity casting and hot working processes, and a complex heat treatment process is required, so that no report is provided for die casting application.
Mg-Y-Zn alloys usually incorporate Zr as a grain refining element to refine their coarse microstructure. The currently reported Zr adding modes comprise sponge Zr, halogen salt of Zr, Zn-Zr intermediate alloy, Mg-Zr intermediate alloy and the like, wherein the Mg-Zr intermediate alloy has the advantages of convenient use, less inclusion and fine granularityThe method has the advantages of good effect and the like, and is the main mode for adding Zr at present. There are still many problems: firstly, the preparation process of the Mg-Zr intermediate alloy is complex and has high energy consumption, so that the price of the Mg-Zr intermediate alloy is high, and the product cost can be increased by refining the crystal grains by using the Mg-Zr intermediate alloy; secondly, Zr has strong chemical activity and is easy to react with atmosphere and furnace gas at high temperature, and when a steel crucible is used and the temperature of a melt is higher than 750 ℃, Zr is easy to react with Fe in the crucible to generate a stable intermetallic compound Fe2Zr, all of which result in high Zr loss; much Zr in Mg-Zr intermediate alloy exists in the form of large-size simple substance Zr particles, the Zr particles are difficult to dissolve in the melt due to the high melting point (1852 ℃) of Zr, and the density of Zr is far higher than that of magnesium melt (the density of Zr is 6.52 g/cm)3The density of the pure magnesium melt was 1.58g/cm3) And is liable to precipitate to the bottom of the crucible, resulting in a low yield of Zr.
Disclosure of Invention
The invention provides a high-strength-toughness heat-resistant die-casting Mg-Y alloy and a preparation method thereof by pressure casting, aiming at solving the industrial problem that the application of the existing die-casting magnesium alloy is greatly limited because the performance of A380 constant-pressure die-casting aluminum alloy can not be achieved due to insufficient strength and heat resistance, and the alloy is subjected to pressure casting, wherein the room-temperature tensile strength of the die-casting alloy reaches 315MPa, the high-temperature tensile strength at 200 ℃ reaches 210MPa, and the room-temperature elongation reaches 12.0%.
The purpose of the invention is realized by the following technical scheme:
in a first aspect, the invention provides a high-strength and high-toughness heat-resistant die-casting Mg-Y alloy, which comprises the following elements in percentage by mass: 2.5-5.0% of Y, 1.0-4.0% of Zn, 0.5-1.2% of Al, 0.1-0.3% of Mn, 0.01-0.08% of M, and the balance of Mg and other inevitable impurities; wherein the mass fraction of magnesium is not less than 89%, and M is a combined element containing at least one element of Ti and B.
Preferably, in the alloy composition elements, the mass ratio of Zn to Y is 0.3-1.0.
Preferably, in the alloy composition elements, the mass ratio of (Zn + Al)/Y is 0.5-1.2.
Preferably, the M comprises the following elements in percentage by mass based on the total amount of all elements in the alloy: 0.01 to 0.05 percent of Ti and 0.01 to 0.03 percent of B.
One of the innovative ideas of the high-strength high-toughness heat-resistant die-casting Mg-Y alloy provided by the invention is as follows: the alloy design adopts cheap Zn element and rare earth Y element to form a ternary Mg-Y-Zn strengthening phase with matrix Mg element. In the range of 0.3-1.0 mass ratio of Zn/Y, on one hand, the alloy of the invention mainly forms LPSO phase (Mg) with long-period stacking ordered structure12ZnY) and face-centered cubic structure W phase (Mg)3Zn3Y2) The high-melting-point phases are adopted, and compared with binary Mg-Y strengthening, the ternary strengthening phase has better high-temperature stability in a magnesium matrix, avoids performance reduction caused by dissolution of a precipitation strengthening phase, effectively enhances the room-temperature mechanical property and high-temperature property of the high-strength high-toughness die-casting heat-resistant Mg-Y alloy, and particularly improves the high-temperature creep property at 300 ℃ by more than one order of magnitude; on the other hand, the invention overcomes the defect that the traditional Mg-Zn-Y alloy is easy to generate heat crack due to overlarge solidification interval caused by overhigh Zn content, and can not ensure the toughness and the die-casting performance of the alloy.
The invention provides a second innovative idea of the high-strength high-toughness heat-resistant die-casting Mg-Y alloy, which is as follows: the precipitated phases of Mg-Y-Zn alloy are often in a coarse network structure under the conventional solidification condition, the mechanical properties of the Mg-Y-Zn alloy are deteriorated, and the size of the precipitated phases must be adjusted to play the role of the strengthening phase through hot deformation or heat treatment solid solution and aging. Zr is usually added into the alloy as a grain refining element, the alloy element of the invention contains Al, Mn and rare earth Y alloy elements, and the elements are combined with Zr to form Al3Zr and the like are precipitated on the bottom of the crucible to prevent the crystal grain refinement of zirconium. On the other hand, researches show that the Mg-Y-Zn alloy refined by adding Zr has poor structure thermal stability, and crystal grains are rapidly coarsened when the temperature is kept at 550 ℃, so that the high-temperature performance is greatly reduced. The alloy of the invention is added with 0.5 to 1.2 percent of Al of low melt to replace Zr to form dispersed Al with high melting point2The Y phase not only refines the structure of the alloy, but also ensures the high-temperature stability of the magnesium alloy structure with high-temperature phases such as LPSO and the like. Meanwhile, Al and a small amount of Ti and B form composite grainsThe alloy structure is further refined and the toughness of the alloy is improved. The alloy element of the invention is added with a small amount of Mn, which not only can promote the formation of LPSO phase, improve the high-temperature stability of the alloy, but also can improve the corrosion resistance of the magnesium alloy.
The invention provides the third innovative idea of the high-strength high-toughness heat-resistant die-casting Mg-Y alloy, which is as follows: the mass ratio of Zn/Y is limited to be 0.3-1.0 and the mass ratio of (Zn + Al)/Y is limited to be 0.5-1.2, so that the solidification interval of the alloy is ensured to be small, the hot cracking tendency of the Mg-Y-Zn alloy in the die casting process is overcome, and the die casting process performance of the alloy is improved.
In a second aspect, the invention provides a preparation method of a high-strength and high-toughness heat-resistant die-casting Mg-Y alloy, which comprises the following steps:
(1) calculating the dosage of the required raw materials according to the Mg-Y alloy components and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and Mg-Y and Mg-Mn intermediate alloys, and drying and preheating to 200 ℃;
(2) melting an industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, introducing protective gas, and adding the rest of the industrial pure magnesium ingot;
(3) after the industrial pure magnesium ingot is completely melted, heating to 700-710 ℃, adding the industrial pure zinc, the Mg-Y and the Mg-Mn intermediate alloy for 2-4 times, keeping the temperature constant at 700-710 ℃ until the industrial pure magnesium ingot is completely melted and preserving the heat for 30 minutes;
(4) heating to 730 ℃ in 40-60 minutes before pressure casting, adding a refining agent for refining after the industrial pure aluminum ingot and the Al-M intermediate alloy are sequentially added to wait for complete melting, and heating the furnace to 750-760 ℃ for heat preservation and standing for 10-20 minutes to promote inclusion settlement to obtain a magnesium alloy melt;
(5) and cooling the magnesium alloy melt to 720-740 ℃, skimming surface scum, pressing the magnesium alloy melt into a die-casting die preheated to 180-250 ℃ at a speed of 4-15 m/s, and cooling to obtain the high-strength high-toughness heat-resistant die-casting Mg-Y alloy.
Preferably, the intermediate alloy containing Mg-Y is MgY25 or MgY30, the intermediate alloy containing Mg-Mn is MgMn10, and the Al-M intermediate alloy is at least one of AlTi5B1, AlB3, AlB8, AlTi5 or AlTi 10.
Preferably, the refining agent component comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2
Preferably, the addition amount of the refining agent is 1.0-3.5% of the total weight of the raw materials.
Preferably, the refining temperature is 720-730 ℃, and the stirring time of the refining treatment is 10-15 min.
Preferably, the protective gas is argon or SF with 0.2% volume fraction6And CO2The mixed gas of (1).
The preparation method of the high-strength high-toughness heat-resistant die-casting Mg-Y alloy has the beneficial effects that: (1) adding rare earth element Mg-Y intermediate alloy which is easy to burn and lose at the temperature of 700-710 ℃, and melting at low temperature by heat preservation, thereby improving the yield of the rare earth Y; (2) the refining treatment adopts MgCl-free2The special refining agent further reduces the burning loss of the rare earth Y in the refining process.
Compared with the prior art, the invention has the following beneficial effects:
after the high-strength high-toughness heat-resistant die-casting Mg-Y alloy is subjected to pressure casting, the room-temperature tensile strength of the die-casting state alloy reaches 315MPa, the high-temperature tensile strength at 200 ℃ reaches 210MPa, the room-temperature elongation reaches 12.0 percent, and the comprehensive performance reaches the performance of A380 isobaric cast aluminum alloy; the preparation method has the advantages of simple process, high efficiency, suitability for large-scale production and the like, can be used without aging and solution heat treatment, and meets the high-end requirements of industries such as aerospace, automobiles, telecommunication and the like on light weight development.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is an as-cast metallographic structure chart of the die-cast magnesium alloy prepared in example 3.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
Example 1
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: 2.5 percent of Y, 1.0 percent of Zn, 0.5 percent of Al, 0.3 percent of Mn, 0.01 percent of Ti, 0.01 percent of B, and the balance of Mg and other inevitable impurities according to the theoretical proportion.
The preparation method comprises the following steps:
(1) calculating the dosage of the required raw materials according to the Mg-Y alloy components and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY25 and MgMn10, and drying and preheating to 200 ℃; calculating the consumption of the required raw materials according to the components and the stoichiometric ratio of the alloy;
(2) melting an industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, introducing protective gas argon, and adding the rest magnesium ingot;
(3) after the magnesium ingot is completely melted, heating to the temperature of 700-;
(4) heating to 730 ℃ after 40-60 minutes before pressure casting, sequentially adding the industrial pure aluminum ingot, AlTi5B1 and AlB3 intermediate alloy to wait for complete melting, adding a refining agent accounting for 1 percent of the weight of the raw materials to refine at 730 ℃, stirring for 10min during refining treatment, wherein the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. Raising the temperature of the furnace to 750-760 ℃, preserving the heat and standing for 10 minutes to promote the settlement of impurities to obtain a magnesium alloy melt;
(5) and cooling the magnesium alloy melt to 720 ℃, skimming surface scum, pressing the magnesium alloy melt into a die-casting die preheated to 180 ℃ at the speed of 4m/s, and cooling to obtain the high-strength high-toughness heat-resistant die-casting Mg-Y alloy.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃. In the embodiment, the solidification interval of the die-cast magnesium alloy is 80 ℃, the tensile strength at the casting state room temperature is 280MPa, and the elongation is 18 percent; the tensile strength at high temperature of 200 ℃ is 185MPa, and the elongation is 27%.
Example 2
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: according to the theoretical mixture ratio, 5.0 percent of Y, 4.0 percent of Zn, 1.2 percent of Al, 0.1 percent of Mn, 0.08 percent of Ti, and the balance of Mg and other inevitable impurities.
The preparation method comprises the following steps:
(1) calculating the dosage of the required raw materials according to the Mg-Y alloy components and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY30 and MgMn10, and drying and preheating to 200 ℃; calculating the consumption of the required raw materials according to the components and the stoichiometric ratio of the alloy;
(2) melting industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, and introducing protective gas containing 0.2% of SF by volume fraction6And CO2Adding the rest magnesium ingot into the mixed gas;
(3) after the magnesium ingot is completely melted, heating to the temperature of 700-;
(4) heating to 730 ℃ after 40-60 minutes before pressure casting, sequentially adding the industrial pure aluminum ingot and the AlTi5 intermediate alloy to wait for complete melting, adding a refining agent accounting for 3.5 percent of the weight of the raw materials to refine at 730 ℃, and stirring for 10 minutes during refining treatment, wherein the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. Raising the temperature of the furnace to 750-760 ℃, preserving the heat and standing for 10 minutes to promote the settlement of impurities to obtain a magnesium alloy melt;
(5) and cooling the magnesium alloy melt to 740 ℃, skimming surface scum, pressing the magnesium alloy melt into a die-casting die preheated to 250 ℃ at the speed of 15m/s, and cooling to obtain the high-strength high-toughness heat-resistant die-casting Mg-Y alloy.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃, wherein the solidification interval of the die-cast magnesium alloy in the example is 40 ℃, the cast room-temperature tensile strength is 295MPa, and the elongation is 10%; the tensile strength at high temperature of 200 ℃ is 210MPa, and the elongation is 15%.
Example 3
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: 3.0% of Y, 2.0% of Zn, 1.0% of Al, 0.2% of Mn, 0.05% of Ti, 0.03% of B and the balance of Mg and other inevitable impurities according to the theoretical proportion.
The preparation method comprises the following steps: (1) calculating the dosage of the required raw materials according to the Mg-Y alloy components and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY30 and MgMn10, and drying and preheating to 200 ℃; calculating the consumption of the required raw materials according to the components and the stoichiometric ratio of the alloy;
(2) melting an industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, introducing protective gas argon, and adding the rest magnesium ingot;
(3) after the magnesium ingot is completely melted, heating to the temperature of 700-;
(4) heating to 730 ℃ after 40-60 minutes before pressure casting, sequentially adding the industrial pure aluminum ingot, the AlTi10 intermediate alloy and the AlB8 intermediate alloy to wait for complete melting, adding a refining agent accounting for 2.5 percent of the weight of the raw materials to refine at 720 ℃, stirring for 15min, wherein the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. Raising the temperature of the furnace to 750-760 ℃, preserving the heat and standing for 10 minutes to promote the settlement of impurities to obtain a magnesium alloy melt;
(5) and (3) cooling the magnesium alloy melt to 730 ℃, skimming surface scum, pressing the magnesium alloy melt into a die-casting die preheated to 200 ℃ at the speed of 10m/s, and cooling to obtain the high-strength high-toughness heat-resistant die-casting Mg-Y alloy, wherein the as-cast metallographic structure diagram of the alloy is shown in figure 1.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃, wherein the solidification interval of the die-cast magnesium alloy in the example is 50 ℃, the cast room-temperature tensile strength is 305MPa, and the elongation is 14%; the tensile strength at high temperature of 200 ℃ is 193MPa, and the elongation is 20%.
Example 4
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: according to the theoretical mixture ratio, 4.0% of Y, 4.0% of Zn, 1.0% of Al, 0.2% of Mn, 0.08% of B, and the balance of Mg and other inevitable impurities.
The preparation method comprises the following steps:
(1) calculating the dosage of the required raw materials according to the Mg-Y alloy components and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY25 and MgMn10, and drying and preheating to 200 ℃; calculating the consumption of the required raw materials according to the components and the stoichiometric ratio of the alloy;
(2) melting industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, and introducing SF containing 0.2% of volume fraction6And CO2Adding the rest magnesium ingot into the mixed protective gas;
(3) after the magnesium ingot is completely melted, heating to the temperature of 700-;
(4) heating to 730 ℃ after 40-60 minutes before pressure casting, sequentially adding a refining agent accounting for 3.0 percent of the weight of the raw materials for refining after the industrial pure aluminum ingot and the AlB8 intermediate alloy are completely melted, wherein the refining temperature is 720 ℃, the stirring time of the refining treatment is 15 minutes, and the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. FurnaceRaising the temperature to 750-760 ℃, preserving the heat and standing for 10 minutes to promote the settlement of impurities to obtain a magnesium alloy melt;
(5) and cooling the magnesium alloy melt to 720 ℃, skimming surface scum, pressing the magnesium alloy melt into a die-casting die preheated to 220 ℃ at the speed of 8m/s, and cooling to obtain the high-strength high-toughness heat-resistant die-casting Mg-Y alloy.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃, wherein the solidification interval of the die-cast magnesium alloy in the example is 43 ℃, the cast room-temperature tensile strength is 315MPa, and the elongation is 12%; the tensile strength at high temperature of 200 ℃ is 207MPa, and the elongation is 18%.
Example 5
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: 4.0% of Y, 1.2% of Zn, 0.8% of Al, 0.3% of Mn, 0.04% of Ti, 0.04% of B and the balance of Mg and other inevitable impurities according to the theoretical proportion.
The preparation method comprises the following steps: (1) calculating the dosage of the required raw materials according to the Mg-Y alloy components and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY25 and MgMn10, and drying and preheating to 200 ℃; calculating the consumption of the required raw materials according to the components and the stoichiometric ratio of the alloy;
(2) melting an industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, introducing protective gas argon, and adding the rest magnesium ingot;
(3) after the magnesium ingot is completely melted, heating to the temperature of 700-;
(4) heating to 730 ℃ after 40-60 minutes before pressure casting, sequentially adding the industrial pure aluminum ingot, the AlTi5 intermediate alloy and the AlB3 intermediate alloy to wait for complete melting, adding a refining agent accounting for 2.0 percent of the weight of the raw materials to refine at 730 ℃, stirring for 10min during refining treatment, wherein the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. Raising the temperature of the furnace to 750-760 ℃, preserving the heat and standing for 10 minutes to promote the settlement of impurities to obtain a magnesium alloy melt;
(5) and cooling the magnesium alloy melt to 740 ℃, skimming surface scum, pressing the magnesium alloy melt into a die-casting die preheated to 250 ℃ at the speed of 15m/s, and cooling to obtain the high-strength high-toughness heat-resistant die-casting Mg-Y alloy.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃, wherein the solidification interval of the die-cast magnesium alloy in the example is 74 ℃, the cast room-temperature tensile strength is 310MPa, and the elongation is 13%; the tensile strength at high temperature of 200 ℃ is 200MPa, and the elongation is 23%.
Example 6
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: according to the theoretical mixture ratio, 4% of Y, 1% of Zn, 1.0% of Al, 0.2% of Mn, 0.05% of Ti, 0.03% of B, and the balance of Mg and other inevitable impurities.
The preparation method is the same as in example 3.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃, wherein the solidification interval of the die-cast magnesium alloy in the example is 74 ℃, the cast room-temperature tensile strength is 300MPa, and the elongation is 9%; the tensile strength at high temperature of 200 ℃ is 185MPa, and the elongation is 14%.
Example 7
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: 4.5 percent of Y, 1.0 percent of Zn, 0.5 percent of Al, 0.3 percent of Mn, 0.04 percent of Ti, 0.04 percent of B, and the balance of Mg and other inevitable impurities according to the theoretical proportion.
The preparation method is the same as in example 5.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃, wherein the solidification interval of the die-cast magnesium alloy in the example is 82 ℃, the as-cast room-temperature tensile strength is 290MPa, and the elongation is 8%; the tensile strength at high temperature of 200 ℃ is 182MPa, and the elongation is 12%.
Comparative example 1
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: 1.5 percent of Y, 1.0 percent of Zn, 0.5 percent of Al, 0.3 percent of Mn, 0.01 percent of Ti, 0.01 percent of B, and the balance of Mg and other inevitable impurities according to the theoretical proportion.
The preparation method is the same as that of example 1.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃, wherein the solidification interval of the die-cast magnesium alloy in the example is 57 ℃, the cast room-temperature tensile strength is 260MPa, and the elongation is 15%; the tensile strength at high temperature of 200 ℃ is 170MPa, and the elongation is 22%.
Comparative example 2
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: according to the theoretical mixture ratio, 5.0 percent of Y, 4.0 percent of Zn, 1.5 percent of Al, 0.1 percent of Mn, 0.08 percent of Ti, and the balance of Mg and other inevitable impurities.
The preparation method is the same as that of example 2.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃, wherein the solidification interval of the die-cast magnesium alloy in the example is 43 ℃, the cast room-temperature tensile strength is 285MPa, and the elongation is 9%; the tensile strength at high temperature of 200 ℃ is 190MPa, and the elongation is 13%.
Comparative example 3
The high-strength and high-toughness heat-resistant die-casting Mg-Y alloy comprises the following components in percentage by weight: 2.5 percent of Y, 1.0 percent of Zn, 0.5 percent of Al, 0.5 percent of Mn, 0.01 percent of Ti, 0.01 percent of B, and the balance of Mg and other inevitable impurities according to the theoretical proportion.
The preparation method is the same as that of example 1.
Respectively carrying out a-room temperature tensile test on the prepared die-casting magnesium alloy; b, performing high-temperature tensile property test at 200 ℃ after 200-hour heat exposure treatment at 200 ℃, wherein the solidification interval of the die-cast magnesium alloy in the example is 80 ℃, the cast room-temperature tensile strength is 275MPa, and the elongation is 15%; the tensile strength at high temperature of 200 ℃ is 180MPa, and the elongation is 22%.
The invention has many applications, and the above description is only a preferred embodiment of the invention. It should be noted that the above examples are only for illustrating the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications can be made without departing from the principles of the invention and these modifications are to be considered within the scope of the invention.

Claims (7)

1. The high-strength high-toughness heat-resistant die-casting Mg-Y alloy is characterized by comprising the following elements in percentage by mass: 2.5-5.0% of Y, 1.0-4.0% of Zn, 0.5-1.2% of Al, 0.1-0.3% of Mn, 0.01-0.08% of M, and the balance of Mg and other inevitable impurities; wherein, the mass fraction of magnesium is not less than 89%, M is a combined element containing at least one element of Ti and B;
in the alloy composition elements, the mass ratio of (Zn + Al)/Y is 0.5-1.2;
and the M comprises the following elements in percentage by mass based on the total amount of all elements in the alloy: 0.01-0.05% of Ti and 0.01-0.03% of B;
the preparation method of the high-strength high-toughness heat-resistant die-casting Mg-Y alloy comprises the following steps:
(1) calculating the dosage of the required raw materials according to the Mg-Y alloy components and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and Mg-Y and Mg-Mn intermediate alloys, and drying and preheating to 200 ℃;
(2) melting an industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, introducing protective gas, and adding the rest of the industrial pure magnesium ingot;
(3) after the industrial pure magnesium ingot is completely melted, heating to 700-710 ℃, adding the industrial pure zinc, the Mg-Y and the Mg-Mn intermediate alloy for 2-4 times, keeping the temperature constant at 700-710 ℃ until the industrial pure magnesium ingot is completely melted and preserving the heat for 30 minutes;
(4) heating to 730 ℃ in 40-60 minutes before pressure casting, adding a refining agent for refining after the industrial pure aluminum ingot and the Al-M intermediate alloy are sequentially added to wait for complete melting, and heating the furnace to 750-760 ℃ for heat preservation and standing for 10-20 minutes to promote inclusion settlement to obtain a magnesium alloy melt;
(5) and cooling the magnesium alloy melt to 720-740 ℃, skimming surface scum, pressing the magnesium alloy melt into a die-casting die preheated to 180-250 ℃ at a speed of 4-15 m/s, and cooling to obtain the high-strength high-toughness heat-resistant die-casting Mg-Y alloy.
2. The high-toughness heat-resistant die-cast Mg-Y alloy according to claim 1, wherein the alloy constituent elements have a Zn/Y mass ratio of 0.3 to 1.0.
3. The high toughness heat resistant die cast Mg-Y alloy as claimed in claim 1, wherein the intermediate alloy of Mg-Y is MgY25 or MgY30, the intermediate alloy of Mg-Mn is MgMn10, and the Al-M intermediate alloy is at least one of AlTi5B1, AlB3, AlB8, AlTi5, or AlTi 10.
4. The high-strength high-toughness heat-resistant die-casting Mg-Y alloy as claimed in claim 1, wherein the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5% CaF2、15% BaCl2
5. The high-strength high-toughness heat-resistant die-casting Mg-Y alloy as claimed in claim 1, wherein the addition amount of the refining agent is 1.0-3.5% of the total weight of the raw materials.
6. The high-strength high-toughness heat-resistant die-casting Mg-Y alloy as claimed in claim 1, wherein the refining temperature is 720-730 ℃, and the stirring time for refining treatment is 10-15 min.
7. The high toughness heat resistant die cast Mg-Y alloy according to claim 1, wherein the protective gas is argon or SF in a volume fraction of 0.2%6And CO2The mixed gas of (1).
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