A method for forming a high-strength and heat-resistant magnesium alloy structural part containing Nd

Abstract

The present invention belongs to the technical field of magnesium alloy forming, and specifically relates to a method for forming a high-strength and heat-resistant magnesium alloy structural component containing Nd; the method specifically comprises the following steps: (1) smelting: melting a pure magnesium ingot and an intermediate alloy; (2) casting: casting a ZM6 ingot at a temperature range of 730 to 780°C; (3) ingot processing: machining the outer circle and both end faces of the cast ZM6 ingot; (4) powdering: using a centrifugal atomization method to form the ZM6 ingot into spherical magnesium alloy powder; (5) program setting: completing the program setting of structural component forming on a magnesium alloy SLM printing device; and (6) component forming: completing the forming of the high-strength and heat-resistant magnesium alloy structural component containing Nd by the SLM printing device. The strength of the cast ZM6 structural component after heat treatment strengthening can be achieved without heat treatment, thereby improving the dimensional accuracy of the structural component.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnesium alloy forming, and in particular relates to a forming method of a Nd-containing high-strength and heat-resistant magnesium alloy structural part. Background Art

[0002] Magnesium alloy is an excellent weight-reducing material. Conventional magnesium alloy is 30% to 60% lighter than aluminum alloy and more than 70% lighter than steel. Its application in engineering can greatly reduce the mass of structural parts. In addition, magnesium alloy has the advantages of good damping and electromagnetic shielding. Due to its excellent performance, magnesium alloy materials are widely used in aerospace, automobile, rail transportation, computer and instrumentation fields.

[0003] Magnesium alloys are classified into wrought magnesium alloys and cast magnesium alloys based on their forming methods. Cast magnesium alloys are suitable for manufacturing complex structural components. ZM6, a high-strength and heat-resistant magnesium alloy containing Nd, is also a common material for cast magnesium alloys. Nd has a relatively low mass fraction among rare earth elements, making Nd-containing magnesium alloys classified as medium rare earth magnesium alloys. Mg-Nd alloys are typical precipitation-strengthened alloys, with the limiting solid solubility of Nd in Mg being 3.6%. The addition of Nd improves the mechanical properties of magnesium alloys at both room and high temperatures. High-strength magnesium alloys containing Nd are typically formed by casting. While cast magnesium alloys can be used to manufacture complex structural components, they suffer from low strength after casting and require heat treatment to enhance their strength. This heat treatment can cause deformation of the components, which can reach up to 3% of the structural dimensions, severely impacting dimensional accuracy. Some components are scrapped due to insufficient dimensional accuracy. Dimensional accuracy and deformation control during heat treatment of cast magnesium alloy components are major challenges. Therefore, improving the inherent strength of the material and reducing subsequent heat treatment processes are key to improving the dimensional accuracy of structural components. SLM (Selective Laser Melting) is a laser additive manufacturing technology that uses computer-aided design and a high-intensity laser as an energy source to melt and fuse powder in selected areas layer by layer, thereby achieving the purpose of component forming. The formed components have high precision and high strength, and do not require subsequent heat treatment to improve their performance. It is a new forming method. Selective laser melting currently has application cases for magnesium alloys. In terms of selective laser melting forming of rare earth magnesium alloys, research has mainly been conducted on Gd-containing magnesium alloys, while research on selective laser melting forming of Nd-containing magnesium alloys is relatively limited. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for forming a Nd-containing high-strength and heat-resistant magnesium alloy structural member.

[0005] This is achieved specifically through the following technical solutions:

[0006] 1. A method for forming a high-strength and heat-resistant magnesium alloy structural component containing Nd, comprising: atomizing a ZM6 ingot into a spherical magnesium alloy powder; and forming the spherical magnesium alloy powder into a magnesium alloy structural component by selective laser melting (SLM) additive manufacturing.

[0007] Furthermore, the molding method specifically comprises the following steps:

[0008] (1) Melting: pure magnesium ingot and Mg-Nd and Mg-Zr master alloys are put into a magnesium alloy melting furnace for melting;

[0009] Furthermore, the input amount of pure magnesium ingot Mg-Nd and Mg-Zr master alloy is in weight units, and the input weight ratio is in accordance with the ZM6 alloy composition ratio specified in HB7780 "Specifications for Magnesium Alloy Castings";

[0010] (2) Casting: At a temperature of 730-780°C, the molten alloy liquid is poured into a sand core using a differential pressure casting device to cast a ZM6 ingot with a diameter of ≤300 and a height of ≤300;

[0011] (3) Ingot processing: The outer circle and both end faces of the ZM6 ingot after casting are machined using a lathe. The surface roughness of the processed ingot is ≤6.3;

[0012] (4) Powdering: The ZM6 ingot was made into spherical magnesium alloy powder with an average particle size of 70 to 150 μm by centrifugal atomization;

[0013] (5) Program setting: Prepare the laser selective melting (SLM) program according to the drawings and other technical documents, and complete the program setting on the magnesium alloy SLM printing equipment;

[0014] (6) Component forming: After the program setting is completed, the laser selective melting additive manufacturing method is adopted and the SLM printing equipment is used to complete the forming of the Nd-containing high-strength and heat-resistant magnesium alloy structural parts.

[0015] Furthermore, in the steps (2), (4) and (6), the temperature, average particle size and printing parameters can be arbitrarily selected within the prescribed range and are not affected by the external dimensions of the molded structural part.

[0016] Furthermore, the printing parameters of step (6) are as follows: laser power is 100-300W, and printing speed is 200-1000mm / s.

[0017] In summary, the beneficial effects of the present invention are as follows: in view of the problem that when magnesium alloys are used in the traditional method to manufacture complex structural parts, the material strength after casting is low and heat treatment is required to improve the material strength, but deformation of the parts will be caused during the heat treatment process, the present invention proposes a method for combining casting, gas atomization powder making method, and laser selective melting additive manufacturing process to be applied to the forming of magnesium alloy structural parts. The structural parts formed by the method of the present invention can achieve the strength of the cast ZM6 structural parts after heat treatment strengthening without heat treatment, thereby avoiding the deformation problem of the structural parts during the heat treatment process and improving the dimensional accuracy of the structural parts.

[0018] The present invention provides a new method for forming magnesium alloy structural parts. In addition to being applicable to high-strength and heat-resistant magnesium alloys containing Nd, it can also be used for forming magnesium alloy structural parts with other components. DETAILED DESCRIPTION

[0019] The specific embodiments of the present invention are further described in detail below, but the present invention is not limited to these embodiments. Any improvement or replacement based on the basic spirit of the present embodiment still falls within the scope of protection required by the claims of the present invention.

[0020] Example 1

[0021] 1. A method for forming a Nd-containing high-strength and heat-resistant magnesium alloy structural part, comprising the following steps:

[0022] (1) Melting: Preheat the pure magnesium ingot and Mg-Nd and Mg-Zr master alloys to remove oil stains. Then, place the magnesium ingot in a crucible preheated at 450°C and added with solvent. After power is supplied, melt the crucible. Then, add other auxiliary materials such as Mg-Nd and Mg-Zr master alloys in sequence until all materials are melted into liquid.

[0023] (2) Casting: The molten alloy liquid is poured into the sand core at a temperature of 755°C and cast into a ZM6 ingot with a diameter of 270 and a height of 290 using a differential pressure casting device;

[0024] (3) Ingot processing: Use a lathe to machine the outer circle and both end faces of the ZM6 ingot after casting, and the surface roughness after processing is ≤6.3;

[0025] (4) Powdering: The ZM6 ingot was made into spherical magnesium alloy powder with an average particle size of 104 μm by centrifugal atomization;

[0026] (5) Program setting: Program setting of 30×65×2 sample on magnesium alloy SLM printing equipment;

[0027] (6) Component forming: SLM printing equipment was used to form Nd-containing high-strength and heat-resistant magnesium alloy specimens, with a printing power of 120W and a printing speed of 400mm / s. The printed parts were tested for mechanical properties, and the test results showed a tensile strength of 159Mpa and an elongation of 1%.

[0028] Example 2

[0029] 1. A method for forming a Nd-containing high-strength and heat-resistant magnesium alloy structural part, comprising the following steps:

[0030] (1) Melting: Preheat the pure magnesium ingot and Mg-Nd and Mg-Zr master alloys to remove oil stains. Then, place the magnesium ingot in a crucible preheated at 450°C and added with solvent. After power is supplied, melt the crucible. Then, add other auxiliary materials such as Mg-Nd and Mg-Zr master alloys in sequence until all materials are melted into liquid.

[0031] (2) Casting: The molten alloy liquid is poured into the sand core at a temperature of 755°C and cast into a ZM6 ingot with a diameter of 270 and a height of 290 using a differential pressure casting device;

[0032] (3) Ingot processing: Use a lathe to machine the outer circle and both end faces of the ZM6 ingot after casting, and the surface roughness after processing is ≤6.3;

[0033] (4) Powdering: The ZM6 ingot was made into spherical magnesium alloy powder with an average particle size of 95 μm by centrifugal atomization;

[0034] (5) Program setting: Program setting of 100×30×10 sample on magnesium alloy SLM printing equipment;

[0035] (6) Component forming: SLM printing equipment was used to form Nd-containing high-strength and heat-resistant magnesium alloy specimens, with a printing power of 150W and a printing speed of 500mm / s. The printed parts were tested for mechanical properties, and the test results showed a tensile strength of 182Mpa and an elongation of 1.2%.

[0036] Example 3

[0037] 1. A method for forming a Nd-containing high-strength and heat-resistant magnesium alloy structural part, comprising the following steps:

[0038] (1) Melting: Preheat the pure magnesium ingot and Mg-Nd and Mg-Zr master alloys to remove oil stains. Then, place the magnesium ingot in a crucible preheated at 450°C and added with solvent. After power is supplied, melt the crucible. Then, add other auxiliary materials such as Mg-Nd and Mg-Zr master alloys in sequence until all materials are melted into liquid.

[0039] (2) Casting: The molten alloy liquid is poured into the sand core at a temperature of 755°C and cast into a ZM6 ingot with a diameter of 270 and a height of 290 using a differential pressure casting device;

[0040] (3) Ingot processing: Use a lathe to machine the outer circle and both end faces of the ZM6 ingot after casting, and the surface roughness after processing is ≤6.3;

[0041] (4) Powdering: The ZM6 ingot was made into spherical magnesium alloy powder with an average particle size of 90 μm by centrifugal atomization;

[0042] (5) Program setting: Program setting of φ30×100 sample on magnesium alloy SLM printing equipment;

[0043] (6) Component forming: SLM printing equipment was used to form Nd-containing high-strength and heat-resistant magnesium alloy specimens. The printing power was 180W and the printing speed was 400mm / s. The mechanical properties of the printed parts were tested. The test results showed that the tensile strength was 185Mpa and the elongation was 0.9%.

[0044] Example 4

[0045] 1. A method for forming a Nd-containing high-strength and heat-resistant magnesium alloy structural part, comprising the following steps:

[0046] (1) Melting: Pure magnesium ingots and Mg-Nd and Mg-Zr master alloys are preheated to remove oil stains. The magnesium ingots are then placed in a crucible preheated to 430°C and solvent is added. After power is supplied, melting begins. Other auxiliary materials such as Mg-Nd and Mg-Zr master alloys are then added in sequence until all materials are melted into liquid.

[0047] (2) Casting: The molten alloy liquid is poured into the sand core at a temperature of 770°C and cast into a ZM6 ingot with a diameter of 250 and a height of 260 using a differential pressure casting device;

[0048] (3) Ingot processing: Use a lathe to machine the outer circle and both end faces of the ZM6 ingot after casting, and the surface roughness after processing is ≤6.3;

[0049] (4) Powdering: The ZM6 ingot was made into spherical magnesium alloy powder with an average particle size of 110 μm by centrifugal atomization;

[0050] (5) Program setting: Program setting of φ30×100 sample on magnesium alloy SLM printing equipment;

[0051] (6) Component forming: SLM printing equipment was used to form Nd-containing high-strength and heat-resistant magnesium alloy specimens. The printing power was 150W and the printing speed was 600mm / s. The mechanical properties of the printed parts were tested. The test results showed that the tensile strength was 176Mpa and the elongation was 1.3%.

[0052] Example 5

[0053] 1. A method for forming a Nd-containing high-strength and heat-resistant magnesium alloy structural part, comprising the following steps:

[0054] (1) Melting: Pure magnesium ingots and Mg-Nd and Mg-Zr master alloys are preheated to remove oil stains. The magnesium ingots are then placed in a crucible preheated to 430°C and solvent is added. After power is supplied, melting begins. Other auxiliary materials such as Mg-Nd and Mg-Zr master alloys are then added in sequence until all materials are melted into liquid.

[0055] (2) Casting: The molten alloy liquid is poured into the sand core at a temperature of 770°C and cast into a ZM6 ingot with a diameter of 250 and a height of 260 using a differential pressure casting device;

[0056] (3) Ingot processing: Use a lathe to machine the outer circle and both end faces of the ZM6 ingot after casting, and the surface roughness after processing is ≤6.3;

[0057] (4) Powdering: The ZM6 ingot was made into spherical magnesium alloy powder with an average particle size of 96 μm by centrifugal atomization;

[0058] (5) Program setting: Program setting of 65×30×5 sample on magnesium alloy SLM printing equipment;

[0059] (6) Component forming: SLM printing equipment was used to form Nd-containing high-strength and heat-resistant magnesium alloy specimens. The printing power was 180W and the printing speed was 600mm / s. The mechanical properties of the printed parts were tested. The test results showed that the tensile strength was 190Mpa and the elongation was 1.1%.

Claims

1. A method for forming a high-strength and heat-resistant magnesium alloy structural part containing Nd, characterized in that: The ZM6 ingot is atomized into spherical magnesium alloy powder, and the spherical magnesium alloy powder is formed into a magnesium alloy structural part by selective laser melting (SLM) additive manufacturing. The process includes the following steps: (1) Melting: pure magnesium ingot and Mg-Nd and Mg-Zr master alloys are put into a magnesium alloy melting furnace for melting; (2) Casting: At a temperature of 730-780°C, the molten alloy liquid is poured into the sand core using differential pressure casting equipment to cast into a ZM6 ingot with a diameter of ≤300 and a height of ≤300; (3) Ingot processing: Use a lathe to machine the outer circle and both end faces of the ZM6 ingot after casting; (4) Powdering: The ZM6 ingot was made into spherical magnesium alloy powder with an average particle size of 70-150 μm by centrifugal atomization; (5) Program setting: Prepare the selective laser melting (SLM) program according to the drawing requirements and complete the program setting on the magnesium alloy SLM printing equipment; (6) Component forming: After the program setting is completed, the laser selective melting additive manufacturing method is used and the SLM printing equipment is used to complete the forming of the Nd-containing high-strength and heat-resistant magnesium alloy structural parts; The printing parameters of step (6) are as follows: laser power is 100-300W, and printing speed is 200-1000mm / s.

2. The method for forming a Nd-containing high-strength and heat-resistant magnesium alloy structural member according to claim 1, wherein: In the step (3), the surface roughness of the processed ingot is ≤6.3.