Powder for magnesium-aluminum alloy MIM (metal injection molding) and MIM part preparation method thereof

Abstract

The invention relates to powder for magnesium-aluminum alloy MIM and a preparation method of a magnesium-aluminum alloy MIM piece. The powder comprises, by weight, 94%-99.7% of magnesium-aluminum alloy spherical powder, 0.1%-2% of metal manganese powder, 0.1%-2% of metal zirconium powder and 0.1%-2% of metal zinc powder. Wherein the particle size range of the magnesium-aluminum alloy spherical powder is 1-20 [mu] m, and the particle sizes of the metal manganese powder, the metal zirconium powder and the metal zinc powder are 1-5 [mu] m. According to the preparation method of the MIM part, the powder is adopted for preparing a feed, and then the feed is prepared into the MIM part through a powder injection molding process. By optimizing the powder, the strength and toughness of the aluminum-magnesium alloy and the aluminum-magnesium alloy part are enhanced, the corrosion resistance is greatly improved, and the application space of the aluminum-magnesium alloy is expanded.

Description

Technical Field

[0001] The invention relates to metal powder for powder injection and the field of powder injection, and in particular to a powder for magnesium-aluminum alloy MIM and a method for preparing a MIM part thereof. Background Art

[0002] As an important lightweight structural material, magnesium-aluminum alloy has broad application prospects in the industrial field, especially in aerospace, automobile manufacturing and electronic products, due to its unique high strength-to-weight ratio and good casting properties, it is an ideal choice for optimized design and energy conservation and emission reduction.

[0003] However, the current application of magnesium-aluminum alloys is restricted by their own performance limitations, so they cannot meet the use requirements in some usage scenarios. If the existing aluminum-magnesium alloys can be effectively improved in strength, toughness and corrosion resistance, their application scenarios can be more diverse.

[0004] Therefore, how to improve the poor performance and corrosion resistance of magnesium-aluminum alloys is crucial to expanding their applications in extreme environments. Summary of the invention

[0005] The first object of the present invention is to provide a magnesium-aluminum alloy MIM powder, wherein the strength and toughness of the material are improved by the addition of manganese metal, the corrosion resistance is improved by the addition of zirconium metal, and the strength and corrosion resistance of the material can be further improved by the addition of zinc metal.

[0006] The technical solution for achieving the first object of the present invention is: the powder for MIM of magnesium-aluminum alloy in the present invention includes 94 wt%~99.7 wt% of magnesium-aluminum alloy spherical powder, 0.1 wt%~2 wt% of metal manganese powder, 0.1wt%~2 wt% of metal zirconium powder, and 0.1 wt%~2 wt% of metal zinc powder in weight percentage; the particle size range of the magnesium-aluminum alloy spherical powder is 1~20μm, and the particle sizes of the metal manganese powder, the metal zirconium powder, and the metal zinc powder are all 1~5μm.

[0007] Furthermore, the material grade of the above-mentioned magnesium-aluminum alloy spherical powder is AZ91D.

[0008] As an optimized design, the powder comprises 0.5wt% manganese metal powder, 0.5wt% zirconium metal powder, 0.3wt% zinc metal powder, and the rest is magnesium-aluminum alloy spherical powder.

[0009] The second object of the present invention is a method for preparing a magnesium-aluminum alloy MIM part, which can obtain an aluminum-magnesium alloy part with a complex structure through the MIM process so that it can be applied to the fields of aerospace, automobile, electronics, etc.

[0010] The technical solution for achieving the second object of the present invention is: the method for preparing an aluminum-magnesium alloy MIM part in the present invention comprises the following steps: S1, mixing the above-mentioned magnesium-aluminum alloy MIM powder with a binder to form a feed; S2, injecting the feed material into a green body; S3, degreasing the green body to obtain a degreased body; S4, sintering the debinded blank to obtain a sintered part; S5. Place the sintered part into a metal furnace for heat treatment to obtain a final part.

[0011] Furthermore, the binder accounts for 35% to 45% of the above feed, and the components of the binder are: 75% to 80% polyoxymethylene, 5% to 10% polyethylene, 5% to 10% polypropylene, 3% to 5% lubricant and 1% to 3% antioxidant.

[0012] Further, in the above step S3, a degreased blank is obtained by acid degreasing; wherein the conditions for acid degreasing are: a vacuum degree of 10 -2 Pa~10 -4 Pa, temperature is 50℃~200℃, time is 4 hours~8 hours; acid degreasing medium is oxalic acid; during acid degreasing, the green body is placed on a degreasing plate with holes, and then placed in an oxalic acid furnace for degreasing; the degreasing plate is made of metal molybdenum plate; the degreasing atmosphere is N2, and the purity is 99.999%; before degreasing begins, the furnace cavity needs to be cleaned first, the specific process is 120~150℃, and the heat preservation is 30~90 minutes; during the degreasing process, the acid inlet amount is set to 0.1~0.9g / min.

[0013] Furthermore, the technical parameters of sintering in step S4 are: vacuum degree is 10 -2 Pa~10 -4 Pa, firstly, heat up to 200℃ at 3℃ / min and keep it for 1h for pre-alloying to discharge the gas in the matrix, then heat up to 550~650℃ at 2℃ / min and keep it for 5~6 hours; during the sintering process, argon with a purity of 99.99% should be used in the heat stripping stage; before entering the furnace, metal molybdenum plates need to be placed around the product to surround the entire product, and sponge titanium should be sprinkled at the joints of the metal molybdenum plates to allow it to fully absorb the oxygen in the furnace during the sintering process.

[0014] Furthermore, the heat treatment parameters in the above step S5 are: first preheating to 200-300°C, keeping warm for 15 minutes, so that the material is evenly heated, then heating to 400-500°C, keeping warm for 3-7 hours, then cooling to 130-160°C at a cooling rate of 30-60°C / min, and keeping warm at this temperature for 10-15 hours.

[0015] The present invention has positive effects: the present invention improves the poor mechanical properties and corrosion resistance of magnesium-aluminum alloy by adding a certain amount of metal powder to magnesium-aluminum alloy powder. Zinc and magnesium form a strengthening phase Mg / Zn2, which can enhance the mechanical properties of the alloy; zirconium and aluminum form a ZrAl3 compound, which can hinder the recrystallization process, thereby refining the recrystallized grains, and refining the grains can effectively improve the material properties; manganese can form a dispersed intermetallic compound MnAl6 with aluminum, which hinders the growth of grains and plays a role in refining grains. DETAILED DESCRIPTION

[0016] (Example 1) In this embodiment, the aluminum-magnesium alloy MIM powder includes 0.5wt% manganese metal powder, 0.5wt% zirconium metal powder, 0.3wt% zinc metal powder, and the rest is magnesium-aluminum alloy spherical powder; the particle size of the magnesium-aluminum alloy spherical powder is 1-20μm (D50: 10-13μm), and the particle sizes of the metal manganese powder, metal zirconium powder, and metal zinc powder are all 1-5μm. The material grade of the magnesium-aluminum alloy spherical powder is AZ91D.

[0017] The preparation method of the aluminum-magnesium alloy MIM part in this embodiment includes the following steps: S1. Mix the aluminum-magnesium alloy MIM powder and a binder to form a feed; wherein the ratio of the aluminum-magnesium alloy MIM powder to the binder is 1.6; the volume proportion of the aluminum-magnesium alloy MIM powder in the feed is 66%, and the rest is the binder; the components of the binder include 60% to 70% of polyoxymethylene, 12% to 15% of polyethylene, 15% to 20% of polypropylene and 3% to 5% of stearic acid in terms of mass percentage; S2, placing the feed material in an injection molding machine, and forming the injection blank through the mold; the injection parameters are: mold temperature is 80~100℃, feed material heating temperature is 130~180℃, injection pressure is 80~120MPa; holding time is 2~3.5s; S3, degreasing the injection blank to obtain a degreased blank; wherein the conditions for acid degreasing are: vacuum degree of 10 -2 Pa~10 - 4 Pa, temperature is 50℃~200℃, time is 4 hours~8 hours; acid degreasing medium is oxalic acid; during acid degreasing, the green body is placed on a degreasing plate with holes, and then placed in an oxalic acid furnace for degreasing; the degreasing plate is made of metal molybdenum plate, and the purpose of using the metal molybdenum plate is to prevent some impurities in the ceramic plate from entering the degreasing body; the degreasing atmosphere is N2, and the purity is 99.999%; before degreasing begins, the furnace cavity needs to be cleaned first, the specific process is 120~150℃, and the heat preservation is 30~90 minutes; during the degreasing process, the acid inlet amount is set to 0.1~0.9g / min; S4. Perform high vacuum sintering on the degreased blank to obtain a sintered blank. The specific technical parameters of the sintering are: high vacuum sintering in a metal cavity sintering furnace, the pressure in the furnace is ≤1.0×10-3Pa, the sintering temperature is 550℃, and the insulation time is 10h. During the sintering process, argon with a purity of 99.99% should be used in the heat removal stage. Before entering the furnace, a metal molybdenum plate needs to be placed around the product to surround the entire product, and sponge titanium is sprinkled at the joints of the metal molybdenum plate to fully absorb the oxygen in the furnace during the sintering process. S5. The sintered parts are heat treated. The heat treatment process is as follows: first, preheat to 200-300°C for preheating, and keep warm for 15 minutes so that the material is evenly heated, then heat up to 400-500°C, keep warm for 3-7 hours, then cool to 130-160°C at a cooling rate of 30-60°C / min, and keep warm at this temperature for 10-15 hours.

[0018] The density of the sintered parts is 99.5%, the tensile strength is 400MPa, and the yield strength is 350MPa.

[0019] (Example 2) In this embodiment, the aluminum-magnesium alloy MIM powder includes 0.3wt% manganese metal powder, 0.3wt% zirconium metal powder, 05wt% zinc metal powder, and the rest is magnesium-aluminum alloy spherical powder; the particle size of the magnesium-aluminum alloy spherical powder is 1-20μm (D50: 10-13μm), and the particle sizes of the metal manganese powder, metal zirconium powder, and metal zinc powder are all 1-5μm. The material grade of the magnesium-aluminum alloy spherical powder is AZ91D.

[0020] The preparation method of the aluminum-magnesium alloy MIM part in this embodiment includes the following steps: S1. Mix the above-mentioned magnesium-aluminum alloy MIM powder and a binder to form a feed; wherein the ratio of the aluminum-magnesium alloy MIM powder to the binder is 1.6; the volume proportion of the aluminum-magnesium alloy MIM powder in the feed is 66%, and the rest is the binder; the components of the binder include 60% to 70% of polyoxymethylene, 12% to 15% of polyethylene, 15% to 20% of polypropylene and 3% to 5% of stearic acid in terms of mass percentage; S2, placing the feed material in an injection molding machine, and forming the injection blank through the mold; the injection parameters are: mold temperature is 80~100℃, feed material heating temperature is 130~180℃, injection pressure is 80~120MPa; holding time is 2~3.5s; S3, degreasing the injection blank to obtain a degreased blank; wherein the conditions for acid degreasing are: vacuum degree of 10 -2 Pa~10 - 4Pa, temperature is 50℃~200℃, time is 4 hours~8 hours; acid degreasing medium is oxalic acid; during acid degreasing, the green body is placed on a degreasing plate with holes, and then placed in an oxalic acid furnace for degreasing; the degreasing plate is made of metal molybdenum plate, and the purpose of using the metal molybdenum plate is to prevent some impurities in the ceramic plate from entering the degreasing body; the degreasing atmosphere is N2, and the purity is 99.999%; before degreasing begins, the furnace cavity needs to be cleaned first, the specific process is 120~150℃, and the heat preservation is 30~90 minutes; during the degreasing process, the acid inlet amount is set to 0.1~0.9g / min; S4. Perform high vacuum sintering on the degreased blank to obtain a sintered blank. The specific technical parameters of the sintering are: high vacuum sintering in a metal cavity sintering furnace, the pressure in the furnace is ≤1.0×10-3Pa, the sintering temperature is 550℃, and the holding time is 10h. During the sintering process, argon with a purity of 99.99% should be used in the heat removal stage. Before entering the furnace, a metal molybdenum plate needs to be placed around the product to surround the entire product, and sponge titanium is sprinkled at the joints of the metal molybdenum plate to fully absorb the oxygen in the furnace during the sintering process. By fully absorbing oxygen, the oxidation of the sintered parts by oxygen can be prevented. S5. The sintered parts are heat treated. The heat treatment process is as follows: first, preheat to 200-300°C for preheating, and keep warm for 15 minutes so that the material is evenly heated, then heat up to 400-500°C, keep warm for 3-7 hours, then cool to 130-160°C at a cooling rate of 30-60°C / min, and keep warm at this temperature for 10-15 hours.

[0021] The density of the sintered parts is 98.9%, the tensile strength is 350MPa, and the yield strength is 300MPa.

[0022] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A magnesium aluminum alloy MIM powder, characterized in that: According to weight percentage, it includes 94 wt %~99.7 wt % of magnesium-aluminum alloy spherical powder, 0.1 wt %~2 wt % of metal manganese powder, 0.1 wt %~2 wt % of metal zirconium powder, and 0.1wt %~2 wt % of metal zinc powder; the particle size range of the magnesium-aluminum alloy spherical powder is 1~20μm, and the particle sizes of the metal manganese powder, the metal zirconium powder, and the metal zinc powder are all 1~5μm.

2. The magnesium-aluminum alloy MIM powder according to claim 1, characterized in that: The material grade of the magnesium-aluminum alloy spherical powder is AZ91D.

3. The magnesium-aluminum alloy MIM powder according to claim 1, characterized in that: According to weight percentage, it includes 0.5wt% of manganese metal powder, 0.5wt% of zirconium metal powder, 0.3wt% of zinc metal powder, and the rest is magnesium-aluminum alloy spherical powder.

4. A method for preparing an aluminum-magnesium alloy MIM part, characterized in that The following steps are involved: S1. Mixing the magnesium-aluminum alloy MIM powder according to claim 1, 2 or 3 with a binder to form a feed material; S2, injecting the feed material into a green body; S3, degreasing the green body to obtain a degreased body; S4, sintering the debinded blank to obtain a sintered part; S5. Place the sintered part into a metal furnace for heat treatment to obtain a final part.

5. The method for preparing an aluminum-magnesium alloy MIM part according to claim 4, characterized in that: The binder accounts for 35% to 45% of the feed, and the components of the binder are: 75% to 80% polyoxymethylene, 5% to 10% polyethylene, 5% to 10% polypropylene, 3% to 5% lubricant and 1% to 3% antioxidant.

6. The method for preparing an aluminum-magnesium alloy MIM part according to claim 4, characterized in that: In step S3, a degreased blank is obtained by acid degreasing; wherein the conditions for acid degreasing are: a vacuum degree of 10 -2 Pa~10 -4 Pa, temperature is 50℃~200℃, time is 4 hours~8 hours; acid degreasing medium is oxalic acid; during acid degreasing, the green body is placed on a degreasing plate with holes, and then placed in an oxalic acid furnace for degreasing; the degreasing plate is made of metal molybdenum plate; the degreasing atmosphere is N2, and the purity is 99.999%; before degreasing begins, the furnace cavity needs to be cleaned first, the specific process is 120~150℃, and the heat preservation is 30~90 minutes; during the degreasing process, the acid inlet amount is set to 0.1~0.9g / min.

7. The method for preparing an aluminum-magnesium alloy MIM part according to claim 4, characterized in that: The technical parameters of sintering in step S4 are: vacuum degree is 10 -2 Pa~10 -4 Pa, firstly, heat up to 200℃ at 3℃ / min and keep it for 1h for pre-alloying to discharge the gas in the matrix, then heat up to 550~650℃ at 2℃ / min and keep it for 5~6 hours; during the sintering process, argon with a purity of 99.99% should be used in the heat stripping stage; before entering the furnace, metal molybdenum plates need to be placed around the product to surround the entire product, and sponge titanium should be sprinkled at the joints of the metal molybdenum plates to allow it to fully absorb the oxygen in the furnace during the sintering process.

8. The method for preparing an aluminum-magnesium alloy MIM part according to claim 4, characterized in that: The heat treatment parameters in step S5 are: first preheating to 200-300°C, keeping warm for 15 minutes, so that the material is evenly heated, then heating to 400-500°C, keeping warm for 3-7 hours, then cooling to 130-160°C at a cooling rate of 30-60°C / min, and keeping warm at this temperature for 10-15 hours.