Disclosure of Invention
The invention aims to provide a high-strength high-corrosion-resistance magnesium alloy and a preparation method thereof, which are characterized in that the strength and the formability of the magnesium alloy are improved and the corrosion resistance of the AZ80 magnesium alloy is improved by adjusting alloy components on the basis of the AZ80 magnesium alloy and adding La-rich misch metal.
The high-strength high-corrosion-resistance magnesium alloy comprises, by weight, 7.0-8.5% of Al, 0.3-0.5% of Zn, 0-0.1% of Mn, 1.5-2.0% of La-rich mischmetal, and the balance of Mg and unavoidable impurities; the La-rich mischmetal contains La and Ce, and the weight ratio of La to Ce is 2: 1-3: 1; the tensile strength is 350-380 MPa, and the yield strength is 250-290 MPa.
The high-strength and high-corrosion-resistance magnesium alloy contains 0.01-0.03 wt% of Fe and less than or equal to 0.01 wt% of other impurities.
The elongation of the high-strength and high-corrosion-resistance magnesium alloy is 16-21%.
The preparation method of the high-strength high-corrosion-resistance magnesium alloy comprises the following steps:
1. preparing a magnesium ingot, a zinc block, an aluminum block, manganese chloride particles and an Mg-La-rich mixed rare earth intermediate alloy according to the components, wherein the Mg-La-rich mixed rare earth intermediate alloy contains 20-30% of La and Ce according to the weight percentage, and the weight ratio of La to Ce is 2: 1-3: 1;
2. under the condition of protective atmosphere, adding a magnesium ingot into a smelting resistance furnace for melting, and setting the melting temperature to be 750 +/-5 ℃ to obtain a magnesium melt;
3. at SF6With CO2Under the condition of mixed protective atmosphere, melting the aluminum block in another melting resistance furnace at the melting temperature of 750 +/-5 ℃ to obtain an aluminum melt; sequentially adding a zinc block and Mg-La-rich mischmetal intermediate alloy into the aluminum melt, and simultaneously adding No. 5 flux; when the high-strength high-corrosion-resistance magnesium alloy contains manganese, adding the manganese chloride particles after adding the zinc blocks; after all the materials are melted, obtaining a mixed melt;
4. at SF6With CO2Adding the mixed solution into a magnesium melt under the condition of mixed protective atmosphere, refining at 750 +/-5 ℃ for 30-40 min, standing for 30-60 min, and cooling to 690-700 ℃ in the standing process to prepare a magnesium alloy melt;
5. casting the magnesium alloy melt by adopting an electromagnetic semi-continuous casting system, starting the electromagnetic system to electromagnetically stir the magnesium alloy melt and the cast ingot when the casting is started, wherein the electromagnetic frequency is 15-30 Hz until the casting is finished, and obtaining a magnesium alloy cast ingot;
6. placing a magnesium alloy ingot into a muffle furnace, and then carrying out two-stage homogenization treatment; wherein the temperature of the first-stage homogenization treatment is 180-250 ℃, and the time is 5-8 h; the temperature of the second-stage homogenization treatment is 350-420 ℃, and the time is 10-15 hours; removing oxide skin on the surface after two-stage homogenization treatment to obtain an ingot blank;
7. keeping the temperature of the ingot blank at 280-320 ℃ for 1-3 hours, and then carrying out hot extrusion on a vertical extruder, wherein the speed of an extrusion outlet is 0.2-0.5 mm/s, the temperature of an extrusion cylinder and a die is 280-320 ℃ during hot extrusion, and the extrusion ratio is more than or equal to 15: 1; and obtaining the high-strength high-corrosion-resistance magnesium alloy after hot extrusion.
In the step 2, the protective atmosphere is argon atmosphere.
The dosage of the No. 5 fusing agent is 0.2-0.4% of the total weight of the magnesium ingot, the zinc block, the aluminum block, the manganese chloride and the Mg-La-rich mixed rare earth intermediate alloy.
The particle size of the manganese chloride particles is 1-3 mm.
In the above-mentioned steps 3 and 4, SF6With CO2SF of mixed protective atmosphere6With CO2The volume ratio of (1) to (3-5).
The La and Ce light rare earth elements with lower cost are selected as the modification elements of the magnesium alloy, and the method is an important direction for researching the modified magnesium alloy; for AZ series magnesium alloy, most of the light rare earth elements can form a heat stable intermetallic compound with Al element in the alloying process, and simultaneously the changed Mg17Al12The phase precipitation form and distribution limit dislocation movement in the deformation process, increase the recrystallization nucleation point, inhibit the growth of recrystallization grains, obviously refine the grains, greatly contribute to the improvement of strength, greatly weaken the anisotropy of the magnesium alloy after deformation, form a rare earth texture, and improve the deformability and the formability of the magnesium alloy; the reason why the AZ80 magnesium alloy has poor corrosion resistance is that a large amount of Mg having poor corrosion resistance is used17Al12The phases are distributed at the crystal boundary, and after rare earth elements are added, Mg17Al12The reduction of the phase and the increase of the rare earth phase will greatly improve the corrosion resistance.
The invention has the advantages and beneficial effects that:
1. on the basis of AZ80 magnesium alloy, modifying the alloy by adding La-rich rare earth; the lanthanum-cerium rare earth element has certain solid solubility in the magnesium alloy and preferentially forms a rare earth phase with high melting point and high thermal stability with the Al element; these rare earth phases suppress the brittle second phase Mg17Al12The precipitation and growth of the alloy matrix are increased due to the deformation of the alloy matrix, so that the alloy matrix is strengthened, the crystal boundary structure is improved, the alloy structure is refined, and the dislocation structure generated by the deformation is increased; on the other hand, the hard high-melting-point rare earth has a strong pinning effect relative to the alloy matrix, a dislocation structure is generated around the alloy matrix, recrystallization nucleation points are increased, the structure is refined, the strength and the plasticity of the alloy are improved, and the corrosion resistance of the alloy is optimized;
2. 3.5 wt.% Na of the high-strength and high-corrosion-resistance magnesium alloyThe equal-area corrosion weight of the cl solution after 10 days of corrosion is less than 20mg/cm2(ii) a The excellent performance of the magnesium alloy can meet the strength index of the magnesium alloy as an automobile hub, has good corrosion resistance, can meet the aim of light weight of an automobile, and can enable the magnesium alloy to have great advantages in the application of the automobile hub;
3. the high corrosion resistant magnesium alloy still keeps good corrosion resistance when the Fe content is 0.03-0.1%;
4. the preparation process is simple and easy, and the used rare earth elements are all cheap rare earth, so the preparation cost is low, and the preparation method is suitable for industrial application.
Detailed Description
The No. 5 flux in the embodiment of the invention is a commercially available magnesium alloy refining agent product.
The impurity contents of the magnesium ingot, the zinc block, the aluminum block, the manganese chloride and the Mg-La-rich mixed rare earth intermediate alloy adopted in the embodiment of the invention are all less than or equal to 0.05 percent.
The electromagnetic semi-continuous casting system adopted in the embodiment of the invention is an electromagnetic semi-continuous casting crystallizer (see low-frequency electromagnetic semi-continuous casting AC52 alloy (special metals and non-ferrous alloys, volume 33, 4 th in 2013).
In the embodiment of the invention, the casting speed is 5-60 mm/min.
When the No. 5 fusing agent is added in the embodiment of the invention, the total No. 5 fusing agent is divided into at least 5 parts, and the parts are added in the melting process, and at least 1 part of the No. 5 fusing agent is added into the aluminum melt along with each component.
In the embodiment of the invention, the magnesium alloy ingot is physically cut to a proper size and then placed in a muffle furnace.
Method for producing magnesium alloy ingot in example of the inventionHas a size of
In the embodiment of the invention, the current of the electromagnetic system is 100-140A when electromagnetic stirring is carried out.
The purity of the argon adopted in the embodiment of the invention is more than or equal to 99 percent.
In the embodiment of the invention, the magnesium alloy ingot is subjected to corrosion test, and is soaked in NaCl solution with the weight concentration of 3.5% for ten days to obtain the equal-area corrosion weight of 13-21 mg/cm2。
The following description of the preferred embodiments of the present invention is provided in conjunction with the detailed description of the invention, but it is to be understood that these descriptions are merely intended to further illustrate features and advantages of the invention, and are not intended to limit the scope of the invention as claimed.
Example 1
Preparing a magnesium ingot, a zinc block, an aluminum block, manganese chloride particles and an Mg-La-rich mixed rare earth intermediate alloy, wherein the Mg-La-rich mixed rare earth intermediate alloy contains 30% of La and Ce according to the weight percentage, and the weight ratio of La to Ce is 2: 1; the particle size of the manganese chloride particles is 1-3 mm;
the prepared No. 5 flux is 0.2 percent of the total weight of the magnesium ingot, the zinc block, the aluminum block, the manganese chloride and the Mg-La-rich mixed rare earth intermediate alloy;
under the condition of protective atmosphere, adding a magnesium ingot into a smelting resistance furnace for melting, and setting the melting temperature to be 750 +/-5 ℃ to obtain a magnesium melt; the protective atmosphere is argon atmosphere;
at SF6With CO2Under the condition of mixed protective atmosphere, melting the aluminum block in another melting resistance furnace at the melting temperature of 750 +/-5 ℃ to obtain an aluminum melt; adding zinc blocks, manganese chloride particles and Mg-La-rich mixed rare earth intermediate alloy into the aluminum melt in sequence, simultaneously adding No. 5 flux, and obtaining mixed melt after all materials are melted;
at SF6With CO2Adding the mixed solution into the magnesium melt under the condition of mixed protective atmosphere, refining at 750 +/-5 ℃ for 30min, then standing for 30min, and cooling to 700 ℃ in the standing process to prepare magnesium alloy melt;
SF mentioned above6With CO2In a mixed protective atmosphere of SF6With CO2The volume ratio of (A) to (B) is 1: 3;
casting the magnesium alloy melt by adopting an electromagnetic semi-continuous casting system, starting the electromagnetic system to electromagnetically stir the magnesium alloy melt and the cast ingot when the casting is started, wherein the electromagnetic frequency is 15-30 Hz until the casting is finished, and obtaining a magnesium alloy cast ingot; performing corrosion test on the magnesium alloy ingot, soaking the magnesium alloy ingot in NaCl solution with the weight concentration of 3.5% for ten days, and performing equal-area corrosion on the ingot with the weight of 18mg/cm2;
Placing a magnesium alloy ingot into a muffle furnace, and then carrying out two-stage homogenization treatment; wherein the temperature of the first-stage homogenization treatment is 180 ℃, and the time is 8 h; the temperature of the second-stage homogenization treatment is 350 ℃, and the time is 15 h; removing oxide skin on the surface after two-stage homogenization treatment to obtain an ingot blank;
keeping the temperature of the ingot blank at 280 ℃ for 3h, and then carrying out hot extrusion on a vertical extruder, wherein the extrusion outlet speed is 0.2mm/s, the temperature of an extrusion cylinder and a die is 280 ℃ during hot extrusion, and the extrusion ratio is 15: 1; after hot extrusion, the high-strength high-corrosion-resistance magnesium alloy is obtained, and the components comprise 8.0 percent of Al, 0.5 percent of Zn, 0.1 percent of Mn, 1.2 percent of La, 0.6 percent of Ce and the balance of Mg and inevitable impurities according to weight percentage; wherein the weight percentage of Fe is 0.01-0.03%, and the total weight percentage of other impurities is less than or equal to 0.01%; the tensile strength is 368MPa, and the yield strength is 280 MPa; the elongation is 20.6%;
after the traditional AZ80 magnesium alloy is cast, annealed and extruded to form according to the above mode, the tensile strength is 322MPa, and the yield strength is 210 MPa; the elongation is 15.3%; wherein AZ80 cast ingot is subjected to corrosion test, and the equal-area corrosion weight is 60mg/cm2。
Example 2
The method is the same as example 1, except that:
(1) preparing a magnesium ingot, a zinc block, an aluminum block and an Mg-La-rich mixed rare earth intermediate alloy, wherein the Mg-La-rich mixed rare earth intermediate alloy contains La and Ce by 20% in percentage by weight, and the weight ratio of La to Ce is 3: 1;
(2) the No. 5 flux is 0.3 percent of the total weight of the magnesium ingot, the zinc block, the aluminum block and the Mg-La-rich mixed rare earth intermediate alloy; manganese chloride is not added;
(3) adding the mixed solution into the magnesium melt, refining at 750 + -5 deg.C for 35min, standing for 40min, and cooling to 695 deg.C during standing;
(4) in a mixed protective atmosphere of SF6With CO2The volume ratio of (A) to (B) is 1: 4;
(5) equal area corrosion weight of 16mg/cm in corrosion test2;
(6) The temperature of the first-stage homogenization treatment is 200 ℃, and the time is 7 h; the temperature of the second-stage homogenization treatment is 380 ℃, and the time is 14 h;
(7) keeping the temperature of the ingot blank at 300 ℃ for 2h, and then carrying out hot extrusion on a vertical extruder, wherein the extrusion outlet speed is 0.3mm/s, the temperature of an extrusion cylinder and a die is 300 ℃ during hot extrusion, and the extrusion ratio is 16: 1;
(8) the high-strength high-corrosion-resistance magnesium alloy comprises 7.0 percent of Al, 0.3 percent of Zn, 1.2 percent of La, 0.4 percent of Ce and the balance of Mg and inevitable impurities by weight percentage; 0.02% by weight of Fe; the tensile strength is 372MPa, and the yield strength is 281 MPa; the elongation is 18.2%; the metallographic structure is shown in fig. 1, the scanning structure of an electron microscope is shown in fig. 2, and the stress-strain curve is shown in fig. 3.
Example 3
The method is the same as example 1, except that:
(1) the Mg-La-rich mixed rare earth intermediate alloy contains 25 percent of La and Ce in percentage by weight;
(2) the No. 5 flux is 0.4 percent of the total weight of the magnesium ingot, the zinc block, the aluminum block, the manganese chloride and the Mg-La-rich mixed rare earth intermediate alloy;
(3) adding the mixed solution into the magnesium melt, refining at 750 + -5 deg.C for 40min, standing for 0min, and cooling to 695 deg.C during standing;
(4) in a mixed protective atmosphere of SF6With CO2The volume ratio of (A) to (B) is 1: 5;
(5) equal area corrosion weight of corrosion test 13mg/cm2;
(6) The temperature of the first-stage homogenization treatment is 220 ℃, and the time is 6 h; the temperature of the second-stage homogenization treatment is 400 ℃, and the time is 12 h;
(7) keeping the temperature of the ingot blank at 310 ℃ for 1.5h, and then carrying out hot extrusion on a vertical extruder, wherein the extrusion outlet speed is 0.4mm/s, the temperature of an extrusion cylinder and a die is 310 ℃ during hot extrusion, and the extrusion ratio is 17: 1;
(8) the high-strength high-corrosion-resistance magnesium alloy comprises, by weight, 7.0% of Al, 0.5% of Zn, 0.1% of Mn, 1.0% of La, 0.5% of Ce, and the balance of Mg and unavoidable impurities; 0.03 percent of Fe by weight; the tensile strength is 378MPa, and the yield strength is 285 MPa; the elongation was 17.2%.
Example 4
The method is the same as example 1, except that:
(1) the Mg-La-rich mixed rare earth intermediate alloy contains 25 percent of La and Ce according to weight percentage, and the weight ratio of La to Ce is 3: 1;
(2) the No. 5 flux is 0.3 percent of the total weight of the magnesium ingot, the zinc block, the aluminum block, the manganese chloride and the Mg-La-rich mixed rare earth intermediate alloy;
(3) adding the mixed solution into the magnesium melt, refining at 750 + -5 deg.C for 40min, standing for 60min, and cooling to 690 deg.C during standing;
(4) in a mixed protective atmosphere of SF6With CO2The volume ratio of (A) to (B) is 1: 4;
(5) equal area corrosion weight of 21mg/cm in corrosion test2;
(6) The temperature of the first-stage homogenization treatment is 250 ℃, and the time is 5 h; the temperature of the second-stage homogenization treatment is 420 ℃, and the time is 10 hours;
(7) keeping the temperature of the ingot blank at 320 ℃ for 1h, then carrying out hot extrusion on a vertical extruder, wherein the extrusion outlet speed is 0.5mm/s, the temperature of an extrusion cylinder and a die is 320 ℃ during hot extrusion, and the extrusion ratio is 18: 1;
(8) the high-strength high-corrosion-resistance magnesium alloy comprises 7.5 percent of Al, 0.3 percent of Zn, 0.1 percent of Mn, 1.5 percent of La, 0.5 percent of Ce, and the balance of Mg and inevitable impurities by weight percentage; 0.03 percent of Fe by weight; the tensile strength is 360MPa, and the yield strength is 275 MPa; the elongation is 20.8%.