High-strength Mg-Y-Nd alloy and additive forming and heat treatment method thereof

Abstract

The invention belongs to the field of additive manufacturing, and particularly relates to a high-strength Mg-Y-Nd alloy and an additive forming and heat treatment method thereof. The high-strength Mg-Y-Nd alloy additive forming and heat treatment method comprises the steps that on a WE43 magnesium alloy base plate, an Mg-Y-Nd magnesium alloy welding wire with the diameter being 0.8-2.8 mm is adopted for additive manufacturing, the advancing speed of a welding gun is 2-20 mm / s, the welding current is 60-140 A, the welding voltage is 12-20 V, the wire feeding speed is 4-18 m / min, and the high-strength Mg-Y-Nd alloy is obtained. And after one layer is subjected to additive manufacturing, after the layer is cooled to 20-80 DEG C, polishing is conducted to remove impurities, then the next layer is subjected to additive manufacturing through the reciprocating additive manufacturing method, and the steps are repeated till the Mg-Y-Nd additive manufacturing alloy with 30-60 layers is obtained. The surface of the Mg-Y-Nd additive manufacturing alloy is polished and cleaned, heat preservation is conducted for 0.5-4 h at the temperature of 480-540 DEG C, solution treatment and water quenching are conducted, finally heat preservation is conducted for 10-19 h at the temperature of 170-230 DEG C, aging treatment and water quenching are conducted, and the high-strength Mg-Y-Nd additive manufacturing alloy is obtained.

Description

Technical Field

[0001] The present invention belongs to the field of additive manufacturing, and specifically relates to a high-strength Mg-Y-Nd alloy and an additive forming and heat treatment method thereof. Background Art

[0002] As the lightest metal structural material currently in practical application, magnesium alloy has the characteristics of high specific strength, high specific stiffness, good damping, and superior electromagnetic shielding properties. It is an ideal structural material for lightweighting key components in fields such as aerospace and improving equipment efficiency. However, magnesium alloy has poor ductility and formability at room temperature and is difficult to maintain high strength and plasticity (when strength increases, plasticity decreases, and vice versa). As a result, traditional forming methods consume more energy and time during the manufacturing process, and it is difficult to directly form complex components. In addition, in order to realize the processing of complex functional parts, complex structural parts, and difficult-to-process parts, the existing technology requires the use of complex and precise molds and tooling equipment, which greatly increases the process cycle. In addition, for better forming, long-term high-temperature treatment is often required, which is not conducive to saving energy and shortening the process flow. For example, when using non-melting inert gas shielded arc welding (TIG) to form magnesium alloys, there will be higher energy consumption and higher heat input. When achieving good forming, it will have an adverse effect on mechanical or other properties. This is mainly because the high heat input will cause a large number of large-sized eutectic phases to precipitate, which requires high temperature and long processing time during subsequent processing, ultimately resulting in a significant decrease in the ductility of the material and anisotropy of each layer of the material. In summary: when the existing technology meets the formability requirements, it will have an adverse effect on the mechanical properties such as strength and plasticity of the alloy; when the strong plasticity meets the requirements, the formability will be reduced. That is, it is difficult for the mechanical properties and formability of the alloy to meet the requirements at the same time. In addition, in the process of additive forming of magnesium alloys, the regulation of process parameters is crucial. When using the same equipment for additive manufacturing, changes in process parameters have a significant impact on the properties of the alloy. Therefore, how to simplify the production process of magnesium alloy parts, coordinate the processing samples, processes and process parameters, reduce production costs, improve material utilization and achieve simultaneous improvement in strong plasticity and formability are technical problems that need to be solved urgently. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a high-strength Mg-Y-Nd alloy, and its preparation method comprises the following steps: (1) under protective gas, a magnesium alloy welding wire is additively formed on a magnesium alloy substrate: the vertical distance between the welding gun and the magnesium alloy substrate is 4-30 mm, the welding gun is additively formed in a straight line, the welding gun travel speed is 2-20 mm / s, the welding current is 50-140 A, the welding voltage is 12-20 V, the wire feeding speed is 4-18 m / min, after additively manufacturing one layer, it is cooled to 20-80 ° C and polished to remove impurities, and then a reciprocating additive manufacturing method is used to additively manufacture the next layer, and the layer is cooled to 20-80 ° C and polished to remove impurities, and this cycle is repeated 15-30 times to finally obtain a 30-60-layer Mg-Y-Nd magnesium alloy additive component;

[0004] (2) subjecting the Mg-Y-Nd magnesium alloy additive component obtained in step (1) to solid solution treatment, aging treatment, and room temperature water quenching to obtain a high-strength Mg-Y-Nd alloy; the high-strength Mg-Y-Nd alloy has a tensile strength of ≥462 MPa and an elongation of ≥5.2%;

[0005] The solution treatment is as follows: keeping the temperature at 480-540°C for 0.5-4h;

[0006] The aging treatment is as follows: keeping the temperature at 170-230°C for 10-19 hours;

[0007] The shielding gas is high-purity argon with a purity of ≥99.99%, or a mixture of argon and helium, or a mixture of CO2 and argon; the volume ratio of argon to helium is 1.5-3.5:6.5-8.5; the volume ratio of CO2 to argon is 2-3:97-98; the shielding gas flow rate is 6-26 L / min;

[0008] The magnesium alloy welding wire comprises, by weight percentage, Y 4.9-7.1%, Nd 4.2-5.5%, unavoidable impurity content ≤ 0.02%, and the balance Mg;

[0009] The magnesium alloy substrate is a WE43 magnesium alloy substrate or an AZ31B magnesium alloy substrate;

[0010] The diameter of the magnesium alloy welding wire described in step (1) is 0.8-2.8 mm.

[0011] Furthermore, the vertical distance between the welding gun in step (1) and the magnesium alloy substrate is 5-28 mm.

[0012] Furthermore, the composition of the magnesium alloy welding wire described in step (1) is: Y 5.0-7.0%, Nd 4.3-5.4%.

[0013] Furthermore, the traveling speed in step (1) is 3-19 mm / s, the welding current is 65-135 A, the welding voltage is 13-19 V, and the wire feeding speed is 5-17 m / min.

[0014] Furthermore, the cooling to 25-75° C. in step (1) is followed by grinding to remove impurities.

[0015] Furthermore, the step (1) finally obtains a 35-58-layer Mg-Y-Nd magnesium alloy additive component.

[0016] Furthermore, the diameter of the magnesium alloy welding wire in step (1) is 1.0-2.4 mm.

[0017] Furthermore, the solution treatment in step (1) is carried out by keeping the temperature at 485-535° C. for 0.6-3.5 h.

[0018] Furthermore, the aging treatment in step (1) is carried out by keeping the temperature at 175-225° C. for 10.5-18.5 h. DETAILED DESCRIPTION

[0019] Example 1

[0020] The forming and heat treatment methods of the high-strength Mg-5.1Y-4.3Nd additive manufacturing alloy 1 are as follows:

[0021] The WE43 magnesium alloy substrate is used, and the welding wire is Mg-5.1Y-4.3Nd magnesium alloy welding wire with a diameter of 1.0mm;

[0022] Step 1: Under high-purity argon shielding gas with a purity of ≥99.99%, the gas flow rate is 15 L / min, and the Mg-5.1Y-4.3Nd magnesium alloy welding wire is subjected to 21 reciprocating cycles of additive manufacturing on a magnesium alloy substrate. Each additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 9 mm, the welding gun is additively manufactured in a straight line, the welding gun travel speed is 5 mm / s, the welding current is 70 A, the welding voltage is 13 V, and the wire feeding speed is 5.6 m / min; after each additive manufacturing layer, it is cooled to 30°C, the impurity layer is polished to remove, and the next layer is additively manufactured by a reciprocating additive manufacturing method, and then cooled to 30°C. The additive manufacturing is repeated to finally obtain a magnesium alloy additive manufacturing component, and the number of layers of the additive manufacturing component is 42.

[0023] Step 2: After polishing and cleaning the surface of the additively manufactured component obtained in Step 1, solution treatment and aging treatment are performed, followed by water quenching at room temperature. The solution treatment is performed at 500°C for 3 hours. The surface of the additively manufactured component is then polished and cleaned, followed by aging treatment, and then water quenching at room temperature to obtain a high-strength Mg-5.1Y-4.3Nd additively manufactured alloy 1. The aging treatment is performed at 200°C for 18 hours.

[0024] Example 2

[0025] The forming and heat treatment methods of high-strength Mg-5.3Y-4.5Nd additive manufacturing alloy 2 are as follows:

[0026] The WE43 magnesium alloy substrate is used, and the welding wire is Mg-5.3Y-4.5Nd magnesium alloy welding wire with a diameter of 1.2mm;

[0027] Step 1: Under high-purity argon shielding gas with a purity of ≥99.99%, the gas flow rate is 17 L / min, and Mg-5.1Y-4.3Nd magnesium alloy welding wire is used to perform 22 cycles of additive manufacturing on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 13 mm, the welding gun is additively manufactured in a straight line, the welding gun travel speed is 6 mm / s, the welding current is 80 A, the welding voltage is 14.2 V, and the wire feeding speed is 6.8 m / min; after each additive manufacturing layer, it is cooled to 40°C, and after polishing to remove the impurity layer, a reciprocating additive manufacturing method is used to additively manufacture the next layer, and then cooled to 40°C. Repeat the additive manufacturing process to finally obtain a magnesium alloy additive manufacturing component, and the number of layers of the additive manufacturing component is 44.

[0028] Step 2: After polishing and cleaning the surface of the additively manufactured component obtained in Step 1, solution treatment and aging treatment are performed, followed by water quenching at room temperature. The solution treatment is performed at 510°C for 2 hours. The surface of the additively manufactured component is then polished and cleaned, followed by aging treatment, and then water quenching at room temperature to obtain high-strength Mg-5.3Y-4.5Nd additively manufactured alloy 2. The aging treatment is performed at 210°C for 16 hours.

[0029] Example 3

[0030] The forming and heat treatment methods of high-strength Mg-5.2Y-5.0Nd additive manufacturing alloy 3 are as follows:

[0031] The WE43 magnesium alloy substrate is used, and the welding wire is Mg-5.2Y-5.0Nd magnesium alloy welding wire with a diameter of 1.4mm;

[0032] Step 1: Under high-purity argon shielding gas with a purity of ≥99.99%, the gas flow rate is 19 L / min, and Mg-5.1Y-4.3Nd magnesium alloy welding wire is used to perform 23 cycles of additive manufacturing on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 17 mm, the welding gun is additively manufactured in a straight line, the welding gun travel speed is 8 mm / s, the welding current is 90 A, the welding voltage is 16.8 V, and the wire feeding speed is 7.6 m / min; after each additive manufacturing layer, it is cooled to 50°C, the impurity layer is polished to remove, and the next layer is additively manufactured by a reciprocating additive manufacturing method, and then cooled to 50°C. The additive manufacturing is repeated to finally obtain a magnesium alloy additive manufacturing component, and the number of layers of the additive manufacturing component is 46.

[0033] Step 2: The surface of the additively manufactured component obtained in Step 1 is polished and cleaned, followed by solution treatment and aging treatment, followed by water quenching at room temperature. The solution treatment is performed at 520°C for 2.5 hours. The surface of the additively manufactured component is then polished and cleaned, followed by aging treatment, and then water quenching at room temperature to obtain the high-strength Mg-5.2Y-5.0Nd additively manufactured alloy 3. The aging treatment is performed at 225°C for 17 hours.

[0034] Example 3

[0035] The forming and heat treatment methods of high-strength Mg-5.0Y-5.2Nd additively manufactured alloy 4 are as follows:

[0036] The AZ31 magnesium alloy substrate is used, and the welding wire is Mg-5.0Y-5.2Nd magnesium alloy welding wire with a diameter of 1.6mm;

[0037] Step 1: Under high-purity argon shielding gas with a purity of ≥99.99%, the gas flow rate is 25 L / min, and Mg-4.9Y-5.2Nd magnesium alloy welding wire is used to perform 24 cycles of additive manufacturing on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 20 mm, the welding gun is additively manufactured in a straight line, the welding gun travel speed is 9 mm / s, the welding current is 110 A, the welding voltage is 18.2 V, and the wire feeding speed is 8.4 m / min; after each additive manufacturing layer, it is cooled to 45°C, the impurity layer is polished to remove, and the next layer is additively manufactured by a reciprocating additive manufacturing method, and then cooled to 45°C. The additive manufacturing is repeated to finally obtain a magnesium alloy additive manufacturing component, and the number of layers of the additive manufacturing component is 48.

[0038] Step 2: After polishing and cleaning the surface of the additively manufactured component obtained in Step 1, it undergoes solution treatment and aging treatment, followed by water quenching at room temperature. The solution treatment is performed at 530°C for 0.5 hours. The surface of the additively manufactured component is then polished and cleaned, followed by aging treatment, and then water quenching at room temperature to obtain the high-strength Mg-5.0Y-5.2Nd additively manufactured alloy 4. The aging treatment is performed at 215°C for 15 hours.

[0039] Comparative Example 1

[0040] The forming and heat treatment methods of Mg-7.2Y-3.5Nd additively manufactured alloy 5 are as follows:

[0041] The AZ31 magnesium alloy substrate is used, and the welding wire is Mg-7.2Y-3.5Nd magnesium alloy welding wire with a diameter of 2.9mm;

[0042] Step 1: Under high-purity argon shielding gas with a purity of ≥99.99%, the gas flow rate is 25 L / min, and Mg-7.2Y-3.5Nd magnesium alloy welding wire is used to perform 14 cycles of additive manufacturing on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 3 mm, the welding gun is additively manufactured in a straight line, the welding gun travel speed is 21 mm / s, the welding current is 150 A, the welding voltage is 22 V, and the wire feeding speed is 19 m / min; after each additive manufacturing layer, it is cooled to 100°C, and after polishing to remove the impurity layer, a reciprocating additive manufacturing method is used to additively manufacture the next layer, and then cooled to 100°C. The additive manufacturing is repeated to finally obtain a magnesium alloy additive manufacturing component, and the number of layers of the additive manufacturing component is 28.

[0043] Step 2: After polishing and cleaning the surface of the additively manufactured component obtained in Step 1, it undergoes solution treatment and aging treatment, followed by water quenching at room temperature. The solution treatment is performed at 475°C for 5 hours. The surface of the additively manufactured component is then polished and cleaned, followed by aging treatment, and then water quenching at room temperature to obtain the high-strength Mg-7.2Y-3.5Nd additively manufactured alloy 5. The aging treatment is performed at 250°C for 9 hours.

[0044] The mechanical property test results of the additively manufactured alloys obtained in Examples 1-4 and Comparative Example 1 are shown in Table 1.

[0045] Table 1 Comparison of mechanical properties of additively manufactured alloys obtained in Examples 1-4

[0046]

[0047] As can be seen from Table 1, the additively manufactured alloys obtained in Examples 1-4 have a tensile strength of ≥462 MPa and an elongation of ≥5.2%. There is no anisotropy or cracking between the layers, and the overall material properties are consistent. The process of the present invention is suitable for forming complex and precision alloy parts. Compared with Comparative Example 1, although the comparative example uses similar components and processes as the present invention, the component ratios and process parameters are not within the scope of protection of the claims of the present invention. As a result, the strength and plasticity of the comparative example are indeed lower than that obtained in the present invention. In addition, compared with the prior art, the present invention simultaneously improves the strength and plasticity of the alloy and makes the alloy have better formability, making it suitable for the processing of general-purpose and complex parts.

[0048] Compared with the prior art, the present invention saves the cost of adding raw materials, simplifies the production process of magnesium alloy parts, and coordinates the processing samples, processes and process parameters to achieve reduced production costs and improved material utilization, ultimately overcoming the technical bottlenecks of the prior art that the formability and strength and plasticity are difficult to improve simultaneously and the anisotropy of the mechanical properties of the alloy, thereby achieving simultaneous improvement of strength and plasticity and formability. The processes and parameters adopted in all embodiments of the present invention are different, among which the alloy strength and plasticity obtained in Example 1 are the most excellent. In addition, compared with Comparative Example 1, it is shown that the adjustment of process parameters and the coordinated regulation of the sample to be processed are very important, and it can also be shown that the excellent mechanical properties and formability of the alloy obtained by the present invention are not determined by a certain component, ratio, process and process parameters, but are achieved by the coordinated regulation of welding wire type, welding wire size, process and process parameters, and only the components, component ratios, processes and process parameters within the scope of protection of the claims of the present invention can achieve the preparation of high-strength Mg-Y-Nd additive manufacturing alloys. The present invention also effectively overcomes the anisotropy problem of multi-layer forming alloys, better achieves the simultaneous improvement of alloy formability and strength and plasticity and avoids the occurrence of anisotropy of mechanical properties. The present invention realizes a short-process processing technology while effectively reducing the heat treatment temperature and time and reducing energy loss, completing the precise processing of ordinary or complex magnesium alloys and difficult-to-process magnesium alloy parts, and simultaneously improving the alloy's formability and strong plasticity. From the perspective of organizational structure, the present invention allows the coarse second phase of the alloy to be effectively dissolved back into the matrix, thereby increasing the matrix's solute element content. At the same time, the short-term heat treatment avoids the growth of grains and precipitates a large number of fine nanophases that can play a strengthening role. In addition, the average grain size obtained by the present invention is ≤12μm, which is smaller than the alloy grain size obtained by the prior art, providing a basis for the alloy's high-strength plasticity, and the width error rate between layers is less than 1%, which is significantly lower than the 10% layer-to-layer width error rate of the comparative example, and simultaneously improves the alloy's formability and strong plasticity.

Claims

1. A high-strength Mg-Y-Nd alloy, characterized in that: Its additive forming and heat treatment method includes the following steps: (1) Under a shielding gas, a magnesium alloy welding wire is additively formed on a magnesium alloy substrate: the vertical distance between the welding gun and the magnesium alloy substrate is 4-30 mm, the welding gun is additively formed in a straight line, the welding gun travel speed is 2-20 mm / s, the welding current is 50-140 A, the welding voltage is 12-20 V, the wire feeding speed is 4-18 m / min, after additively manufacturing one layer, it is cooled to 20-80 ° C and polished to remove impurities, and then a reciprocating additive manufacturing method is used to additively manufacture the next layer, and the layer is cooled to 20-80 ° C and polished to remove impurities, and this cycle is repeated 15-30 times to finally obtain a 30-60-layer Mg-Y-Nd magnesium alloy additive component; (2) subjecting the Mg-Y-Nd magnesium alloy additive component obtained in step (1) to solid solution treatment, aging treatment, and room temperature water quenching to obtain a high-strength Mg-Y-Nd alloy; the high-strength Mg-Y-Nd alloy has a tensile strength of ≥462 MPa and an elongation of ≥5.2%; The solution treatment is as follows: keeping the temperature at 480-540°C for 0.5-4h; The aging treatment is as follows: keeping the temperature at 170-230°C for 10-19 hours; The shielding gas in step (1) is high-purity argon with a purity of ≥99.99% or a mixture of argon and helium or a mixture of CO2 and argon; the volume ratio of argon and helium is 1.5-3.5:6.5-8.5; the volume ratio of CO2 and argon is 2-3:97-98; the shielding gas flow rate is 6-26 L / min; the composition of the magnesium alloy welding wire is, by weight percentage, Y4.9-7.1%, Nd4.2-5.5%, the inevitable impurity content is ≤0.02%, and the balance is Mg; the magnesium alloy substrate is a WE43 magnesium alloy substrate or an AZ31B magnesium alloy substrate; the diameter of the magnesium alloy welding wire is 0.8-2.8 mm.

2. The high-strength Mg-Y-Nd alloy according to claim 1, characterized in that: The vertical distance between the welding gun described in step (1) and the magnesium alloy substrate is 5-28 mm.

3. The high-strength Mg-Y-Nd alloy according to claim 1, characterized in that: Calculated by weight percentage, the composition of the magnesium alloy welding wire is: Y 5.0-7.0%, Nd 4.3-5.4%.

4. The high-strength Mg-Y-Nd alloy according to claim 1, characterized in that: The traveling speed described in step (1) is 3-19 mm / s, the welding current is 65-135 A, the welding voltage is 13-19 V, and the wire feeding speed is 5-17 m / min.

5. The high-strength Mg-Y-Nd alloy according to claim 1, characterized in that: After cooling to 25-75° C. in step (1), the product is polished to remove impurities.

6. The high-strength Mg-Y-Nd alloy according to claim 1, characterized in that: The step (1) finally obtains a 35-58-layer Mg-Y-Nd magnesium alloy additive component.

7. The high-strength Mg-Y-Nd alloy according to claim 1, characterized in that: The diameter of the magnesium alloy welding wire described in step (1) is 1.0-2.4 mm.

8. The high-strength Mg-Y-Nd alloy according to claim 1, characterized in that: The solution treatment in step (1) is carried out at 485-535°C for 0.6-3.5 hours.

9. The high-strength Mg-Y-Nd alloy according to claim 1, characterized in that: The aging treatment in step (1) is carried out at 175-225° C. for 10.5-18.5 hours.

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