A method for in-situ precipitation of long-period stacking ordered phase in magnesium-rare earth alloy

Abstract

The application relates to the technical field of metal materials, in particular to a method for in-situ precipitation of a long-period stacking ordered phase of a magnesium-rare earth alloy, which comprises the following steps: preparing a magnesium-based composite powder; the magnesium-based composite powder comprises a magnesium matrix alloy powder and Ni particles; forming through laser additive manufacturing; the application introduces Ni particles into laser additive manufacturing of the magnesium-rare earth alloy to in-situ form a long-period stacking ordered (LPSO) phase, a new method for forming the LPSO phase in laser additive manufacturing of the magnesium-rare earth alloy is verified, and a new approach is provided for design and development of the long-period stacking ordered magnesium alloy.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, specifically to a method for in-situ precipitation of long-period stacked ordered phases in magnesium rare earth alloys using laser additive manufacturing. Background Technology

[0002] The LPSO phase in magnesium alloys is a superior strengthening phase, possessing excellent heat resistance, high tensile strength, and ductility. Its formation is considered one of the most effective methods for developing lightweight, high-strength magnesium alloys at both room and high temperatures. The LPSO phase is commonly found in Mg-RE-Zn alloys (where RE = Y, Nd, Gd, La, Ce, Pr, Tm, Dy, Sm, Ho, Tb, Yb, Er) and MG-XY alloys (X = Zn, Cu). The discovery, composition determination, and development of the highest-strength magnesium alloys were all achieved through research on Mg-Zn-Y alloys. In 2001, Kawamura et al. (developed a rapidly solidified powder metallurgy Mg alloy with excellent tensile strength)... 97 Zn1Y2 alloy (Rapidly solidifiedpowder metallurgy Mg 97 Zn1Y2 alloys with excellent tensile yield strength above 600MPa) were prepared by rapid solidification powder metallurgy to produce as-cast long-period LPSO phase-reinforced Mg alloys with high tensile strength. 97 Zn1Y2 alloy. In 2008, Itoi et al. (A high-strength Mg–Ni–Y alloy sheet with a long-period ordered phase prepared by hot-rolling) [The text abruptly shifts to a seemingly unrelated topic:] ...Zn1Y2 alloy. In 2008, Itoi et al. (A high-strength Mg–Ni–Y alloy sheet with a long-period ordered phase prepared by hot-rolling) ... 90.5 Ni 3.25 Y 6.25 An 18R-type LPSO structural phase was discovered in the alloy. In 2013, Jin et al. (Mg) 88 Formation of LPSO phase in M5Y7 (M = Ti, Ni, and Pb) cast alloy (Formation of long-period stacking ordered structures in Mg) 88 M5Y7 (M = Ti, Ni and Pb) casting alloys) can be produced by adjusting the content of Ni and Y in the as-cast Mg... 88A small amount of 14H-LPSO structure was formed in the Ni5Y7 alloy. In 2014, Wang et al. (Abundant longperiod stacking ordered structure induced by Ni addition into Mg–Gd–Zn alloy) found that adding a small amount of Ni (0.2-2.3 wt.% Ni) to as-cast Mg–Gd-Zn-Ni alloys could not only induce the formation of LPSO phase, but also stimulate Zn to participate in the formation of LPSO phase. Furthermore, the mechanical properties of magnesium alloys containing LPSO phase formed by Ni completely replacing Zn were significantly superior to those of magnesium alloys containing LPSO phase formed entirely by Zn.

[0003] Currently, magnesium alloys containing the LPSO phase are mainly prepared using processes such as rolling, casting, and powder metallurgy. The LPSO phase primarily exists in the Mg-RE-Zn alloy system, while research on its formation in the Mg-RE-Ni system is relatively limited. Existing technology (Xie Weixun. Research on TIG arc additive manufacturing and composite strengthening process of rare earth magnesium alloys containing LPSO phase [D]. Nanjing University of Aeronautics and Astronautics, 2023.) uses Mg-9Gd-4Y-2Zn-0.5Zr (wt.%) rare earth magnesium alloy wire as raw material to study the manufacturing of rare earth magnesium alloys using TIG arc additive manufacturing, aiming to obtain additive components with high forming accuracy and mechanical properties. However, this method involves a large amount of rare earth elements, resulting in high cost, and the volume fraction of the LPSO phase is not ideal. Furthermore, the arc additive manufacturing process suffers from problems such as poor forming accuracy and surface quality, difficulty in controlling heat input, limited material applicability, insufficient process stability, significant challenges in controlling internal defects, high requirements for post-processing, and limited equipment flexibility.

[0004] Therefore, there is an urgent need to design a new technical solution to comprehensively address the problems existing in the background technology. Summary of the Invention

[0005] The purpose of this invention is to provide a method for in-situ precipitation of long-period stacked ordered phases in magnesium rare earth alloys, which can effectively solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for in-situ precipitation of long-period stacked ordered phases in magnesium rare earth alloys includes the following steps:

[0008] S1. Preparation of magnesium-based composite powder; the magnesium-based composite powder includes magnesium matrix alloy powder (WE43 series magnesium alloy powder) and Ni particles, wherein the Ni particles account for 1wt.%-9wt.% of the total weight of the magnesium-based composite powder;

[0009] S2. Forming by laser additive manufacturing; the process parameters for laser additive manufacturing are as follows: laser power is 1500-2000W, scanning speed of the X and Y directions of the deposited sample is 500-1000mm / min, powder feeding rate is 2.0-2.5rpm, powder feeding gas pressure flow rate is 2-5L / min, scanning strategy is: scanning line spacing is 1.2-1.6mm, and after each layer is deposited, the Z direction is raised by 1.0-1.5mm and the deposition experiment is repeated.

[0010] Preferably, the composition of the magnesium matrix alloy powder in step S1, by mass percentage, is: Y: 4.01 wt.%, Nd: 2.46 wt.%, Gd: 1.23 wt.%, Zr: 0.51 wt.%, with the balance being Mg and unavoidable impurities.

[0011] Preferably, the particle size distribution of the magnesium matrix alloy powder is in the range of 75–178 μm.

[0012] Preferably, the amount of Ni particles added is 1 wt.%, 3 wt.%, or 5 wt.% of the total weight of the magnesium-based composite powder.

[0013] Preferably, the average particle size of the Ni particles is 10 μm.

[0014] Preferably, in step S1, the magnesium matrix alloy powder and Ni particles are mixed by a ball milling process. The ball milling process parameters are: ball-to-powder ratio: 5:1; ball milling speed: 200 r / min; ball milling time: 2-3 h; and the oxygen content is guaranteed to be <100 ppm during the ball milling process.

[0015] Preferably, the process parameters for laser additive manufacturing in step S2 are: oxygen content <100ppm, laser power 1800W; X and Y direction scanning speed of the deposited sample: 800mm / min, powder feeding rate: 2.3rpm, powder feeding gas pressure flow rate: 3L / min, scanning strategy: four reciprocating N layers, scanning line spacing of 1.5mm, and Z direction elevation of 1.2mm after each layer deposition.

[0016] Preferably, the laser beam spot diameter is 3 mm.

[0017] The method for in-situ precipitation of long-period stacked ordered phases in magnesium rare earth alloys provided in the above technical solution introduces Ni particles into the laser additive manufacturing of WE43 magnesium rare earth alloys to form long-period stacked ordered (LPSO) phases in situ, providing a new approach for the design of magnesium alloys containing LPSO phases and the preparation of lightweight, high-performance magnesium alloys. Furthermore, after adding 1 wt.%, 3 wt.%, and 5 wt.% metallic Ni powder particles, the volume fractions of the LPSO phase formed in the WE43 magnesium alloy matrix are 14.5%, 15.8%, and 19.2%, respectively. Using the method of this invention, compared with the WE43 matrix, the introduction of 1 wt.%, 3 wt.%, and 5 wt.% metallic Ni results in varying degrees of improvement in tensile strength and elongation. Specifically, the addition of 5 wt.% Ni increases the tensile strength and elongation of the prepared magnesium rare earth alloy by 7.6% and 10.3% respectively compared to the matrix alloy, and by 17.1% and 24.6% respectively compared to the casting process. Attached Figure Description

[0018] Figure 1 Backscattered image of magnesium-based composite powder with 3 wt.% Ni particles added;

[0019] Figure 2 Packing diagram of composite powder after ball milling and mixing with 1 wt.%, 3 wt.%, and 5 wt.% Ni particles;

[0020] Figure 3 Microstructure of the deposited sample after Ni particles and WE43 composite powder were manufactured by laser additive manufacturing: (a) WE43 matrix, (b) 1 wt.% Ni, (c) 3 wt.% Ni and (d) 5 wt.% Ni;

[0021] Figure 4 The image shows the SEM image of the microstructure of the deposited sample (Xie Weixun. Research on TIG arc additive manufacturing and composite strengthening process of rare earth magnesium alloy containing LPSO phase [D]. Nanjing University of Aeronautics and Astronautics, 2023.). The black area in the image is the α-Mg matrix, and the white phase is the generated second phase.

[0022] Figure 5 The room temperature tensile properties of the laser additive manufacturing Ni / WE43 alloy in this embodiment are shown. Detailed Implementation

[0023] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0024] This embodiment provides a method for in-situ precipitation of long-period stacked ordered phases in magnesium rare earth alloys. The specific steps are as follows:

[0025] (1) The selected WE43 magnesium rare earth alloy powder has a particle size distribution range of 75-178 μm and an average particle size of 126.5 μm. The specific ratio of its alloying elements is Y: 4.01 wt.%, Nd: 2.46 wt.%, Gd: 1.23 wt.%, Zr: 0.51 wt.%, with the balance being Mg. 1 wt.%, 3 wt.%, and 5 wt.% metallic Ni powder particles with an average size of 10 μm were introduced into the alloy. The ball milling process was completed in a planetary ball mill at a speed of 200 rpm for 2 hours. The ball milling process strategy was to run for 30 minutes and then rest for 5 minutes, with a total machine running time of 2.25 hours. The ball-to-material ratio was set to 5:1 to ensure uniform mixing of the WE43 alloy powder and metallic Ni powder particles. Figure 1 As shown. The packing diagrams of the three composite powders after ball milling and mixing are as follows. Figure 2 As shown.

[0026] (2) A 15mm thick pure magnesium substrate was selected, and the surface oxide layer was removed by sanding to keep the surface flat. The pure magnesium substrate was placed in a laser powder feeding additive manufacturing platform equipped with a micro-numerical M2P-X100 (G code) motion controller built in the laboratory and filled with an inert argon gas chamber with an oxygen content controlled below 100ppm. The laser used was a YLS-K 10kW high-power fiber laser from IPG, with a laser beam spot diameter of 3mm.

[0027] (3) Under an argon protective atmosphere (oxygen content <100ppm), the following optimized process parameters were used to conduct laser additive manufacturing forming experiments: the laser power was set to 1800W, the X and Y direction scanning speed of the deposited sample was 800mm / min, the powder feeding rate was 2.3rpm, the powder feeding gas pressure flow rate was 3L / min, the scanning strategy was four reciprocating multilayers, the scanning line spacing was 1.5mm, and after each layer was deposited, the Z direction was raised by 1.2mm to repeat the deposition experiment.

[0028] (4) The microstructure of the laser additive manufacturing magnesium rare earth alloy sample prepared by the process described in the above embodiments is as follows: Figure 3 As shown, analysis revealed that the samples exhibited excellent forming quality, free from defects such as porosity and cracks, with a density exceeding 99%. ImageJ software was used to statistically analyze the volume fraction of the in-situ precipitated LPSO phase. After adding 1 wt.%, 3 wt.%, and 5 wt.% metallic Ni powder particles, the volume fractions of the LPSO phase in the WE43 magnesium alloy matrix were 14.5%, 15.8%, and 19.2%, respectively. Figure 4In the existing technology (research on TIG arc additive manufacturing and composite strengthening process of rare earth magnesium alloys containing LPSO phase), magnesium rare earth alloys containing LPSO phase were prepared. According to the ImageJ software, the volume fraction of LPSO phase was 8.5%. Compared with the previous technology, the volume fraction of LPSO phase in the magnesium rare earth alloys prepared in this embodiment was increased by 70.6%, 85.9% and 125.9%, respectively.

[0029] The LPSO phase in magnesium alloys is a superior strengthening phase, possessing excellent heat resistance, high tensile strength, and ductility. Its formation is considered one of the most effective methods for developing lightweight, high-strength magnesium alloys at both room and high temperatures. A suitable volume fraction of LPSO (10-25%) can significantly improve the strength and toughness of magnesium alloys. For example... Figure 5 As shown in Tables 1 and 2, compared with the WE43 matrix, the tensile strength and elongation were improved to varying degrees after the introduction of 1 wt.%, 3 wt.%, and 5 wt.% metallic Ni. Among them, the tensile strength and elongation of the sample increased by 7.6% and 10.3% respectively compared with the matrix alloy, and by 17.1% and 24.6% respectively compared with the casting process.

[0030] Compared with the rare earth element content of the two, the rare earth element content used in the preparation of magnesium rare earth alloy containing LPSO phase (Mg-9Gd-4Y-2Zn-0.5Zr(wt%)) is 13%, while the rare earth element content used in this invention is 7.7wt.%, which reduces the amount of rare earth elements used by 40.8%. Therefore, the cost is reduced significantly, while the volume fraction of LPSO phase obtained is increased significantly.

[0031] The specific conditions for the embodiments and comparative examples are shown in Table 1.

[0032] Table 1

[0033]

[0034] The test results are shown in Table 2.

[0035] Table 2

[0036]

[0037] As shown in Comparative Examples 1 to 3, for WE43 magnesium alloys, neither laser additive manufacturing, arc additive manufacturing, nor casting processes can form the LPSO phase. This is because the main alloying system for forming the LPSO phase is Mg-RE-X, where X (transition elements (Zn, Ni, etc.)) is an essential component. Since WE43 alloy is a Mg-RE system and does not contain transition elements, it cannot form the LPSO phase. From Examples 1 to 3, it is evident that the LPSO phase volume fraction is optimal when using the "laser additive manufacturing + 5% Ni" condition, exhibiting high tensile strength, suitable yield strength, and elongation. This is because during laser additive manufacturing, rapid heating and cooling, along with complex thermal stress, introduce numerous dislocations, vacancies, and other defects into the material. These defects can serve as nucleation sites for the LPSO phase, reducing its nucleation energy and promoting its formation. Furthermore, although the overall cooling rate is fast during laser additive manufacturing, high temperatures are created in the localized areas affected by the laser, allowing alloying elements to acquire sufficient energy for diffusion and migration in a short time, creating conditions for the formation of more LPSO phases. Higher LPSO phase content significantly improves strength. Meanwhile, comparing Comparative Examples 4 and 5, it can be seen that neither "arc additive manufacturing + 5% Ni" nor "casting process + 5% Ni" is as effective as this application. This is because, compared to arc additive manufacturing + 5% Ni and casting process + 5% Ni, the laser additive manufacturing process used in this application has a higher cooling rate, resulting in a finer solidification structure within the magnesium alloy matrix and the formation of a higher content of network LPSO phase distributed along grain boundaries. Figure 3 ).

[0038] Combining Comparative Examples 6 and 7, it can be seen that for the Mg-9Gd-4Y-2Zn-0.5Zr system, although both laser additive manufacturing and arc additive manufacturing processes can increase the volume fraction of the LPSO phase, the improvement is relatively small. Moreover, although the strength obtained is higher than that of this application, the elongation is lower. In addition, the amount of rare earth elements used is 1.7 times that of this application, resulting in a significantly higher cost. In summary, this application has high market application potential in the preparation of high-performance magnesium rare earth alloys containing the LPSO phase.

[0039] The embodiments of the present invention have been described in detail above with reference to the examples. However, the present invention is not limited to the above embodiments. For those skilled in the art, after learning the contents described in the present invention, several equivalent changes and substitutions can be made without departing from the principle of the present invention. These equivalent changes and substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A method for in-situ precipitation of long-period stacked ordered phases in magnesium rare earth alloys, characterized in that, Includes the following steps: S1. Preparation of magnesium-based composite powder; the magnesium-based composite powder includes magnesium matrix alloy powder and Ni particles, wherein the Ni particles account for 5 wt.% of the total weight of the magnesium-based composite powder. S2. Forming by laser additive manufacturing; the process parameters for laser additive manufacturing are as follows: laser power is 1500-2000W, laser beam spot diameter is 3 mm, scanning speed of the X and Y directions of the deposited sample is 500-1000 mm / min, powder feeding rate is 2.0-2.5 rpm, powder feeding gas pressure flow rate is 2-5 L / min, scanning strategy is: scanning line spacing is 1.2-1.6 mm, and after each layer is deposited, the Z direction is raised by 1.0-1.5 mm to repeat the deposition experiment; The composition of the magnesium matrix alloy powder in step S1, by mass percentage, is as follows: Y: 4.01 wt.%, Nd: 2.46 wt.%, Gd: 1.23 wt.%, Zr: 0.51 wt.%, with the balance being Mg and unavoidable impurities; The particle size distribution range of the magnesium matrix alloy powder is 75–178 μm; The process parameters for laser additive manufacturing in step S2 are as follows: oxygen content <100 ppm, laser power 1800 W; X and Y direction scanning speed of the deposited sample: 800 mm / min, powder feed rate: 2.3 rpm, powder feed gas pressure flow rate: 3 L / min, scanning strategy: four reciprocating N layers, scanning line spacing of 1.5 mm, and Z direction elevation of 1.2 mm after each layer deposition.

2. The method for in-situ precipitation of long-period stacked ordered phases in magnesium rare earth alloys according to claim 1, characterized in that: The average particle size of the Ni particles is 10 μm.

3. The method for in-situ precipitation of long-period stacked ordered phases in magnesium rare earth alloys according to claim 1, characterized in that, In step S1, the magnesium matrix alloy powder and Ni particles are mixed by ball milling. The ball milling process parameters are: ball-to-powder ratio: 5:1; ball milling speed: 200 r / min; ball milling time: 2-3 h; and the oxygen content is guaranteed to be <100 ppm during the ball milling process.

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