A plastic working process of a Mg-Gd-Y-Zn-Zr alloy member

Abstract

This invention discloses a plastic processing technology for Mg-Gd-Y-Zn-Zr alloy components. The preparation process includes the following steps: A. Melting and semi-continuous casting Mg-Gd-Y-Zn-Zr alloy bars with a diameter of Φ330mm-430mm; B. Homogenizing annealing of the ingot; C. Turning and blanking to obtain bars with a diameter of Φ290mm-390mm; Before extrusion, the billet and die are held at 380-450℃ for 1-3 hours; After the holding period, the billet is laid horizontally. The process involves: A) Forward extrusion with an extrusion ratio of 4-9 and a hydraulic rod feed speed of 0.5-3.5 mm / s; air cooling after extrusion; B) Machining a cuboid billet with a cross-sectional side length of 35-55 mm and a length of 70-110 mm from the extruded billet; the length direction of the cuboid billet is perpendicular to the extrusion direction; C) Performing 5-13 passes of equal-diameter angular extrusion on the cuboid billet in a die with an included angle of 90°; after deformation, the surface temperature of the billet is 205-305℃, followed by air cooling to room temperature. Using this process, the prepared Mg alloy components exhibit very weak anisotropy in mechanical properties, which can promote the in-depth application of Mg alloy components in transportation, aerospace, and other fields.

Description

Technical Field

[0001] This invention relates to the field of magnesium alloy deformation processing, and particularly to a plastic processing technology for quasi-isotropic magnesium alloy components. Background Technology

[0002] As the lightest practical metallic structural material currently available, magnesium alloys possess advantages such as high specific strength, high specific stiffness, and good damping and vibration reduction properties. They are increasingly replacing aluminum or steel in various applications, accelerating the process of lightweighting structural components. Among them, Mg-RE-Zn alloys containing long-period ordered structure (LPSO) phases exhibit even more outstanding mechanical properties. Currently, the Mg alloy bulk materials with the highest hardness and best overall mechanical properties reported in the literature are all derived from the plastic forming of Mg-RE-Zn alloys.

[0003] However, polycrystalline magnesium alloys typically exhibit preferred crystal orientations (i.e., texture) after plastic deformation. Combined with inhomogeneous microstructures (such as the second phase), this leads to differences in strength and ductility along different directions, with some directions even showing significant weaknesses in mechanical properties. This severely limits the application scenarios of Mg alloy components. For Mg-RE-Zn alloys, inventing a processing technology to make them exhibit quasi-isotropic mechanical properties is of great significance for promoting the in-depth application of Mg alloys in transportation, aerospace, and other fields. Summary of the Invention

[0004] This invention provides a plastic processing technology for Mg-Gd-Y-Zn-Zr alloy components, and the specific technical solution is as follows.

[0005] A. Smelting and semi-continuous casting Mg-Gd-Y-Zn-Zr alloy bars with diameters of Φ330mm-430mm;

[0006] B. Perform homogenization annealing on the ingot;

[0007] C. After homogenization and annealing, the billet is rolled and cut to obtain bars with a diameter of Φ290mm-390mm. Before extrusion, the billet and the die are kept at 380-450℃ for 1-3 hours. After the heat treatment, the billet is removed and placed into the extrusion cylinder for horizontal forward extrusion at an extrusion ratio of 4-9. Bars with a diameter of Φ100-200mm are extruded from the die opening. During horizontal forward extrusion, the hydraulic rod advance speed is 0.5-3.5mm / s. The bars are air-cooled after extrusion.

[0008] D. Machining a cuboid blank with a cross-sectional side length of 35-55mm and a length of 70-110mm from the extruded bar; the length direction of the cuboid blank is perpendicular to the extrusion direction;

[0009] E. Extruding the rectangular billet at a 90° angle in a mold; before extruding, heat the rectangular billet and the mold at 380-430℃ for 1-4 hours; after heat treatment, extrude 5-13 times at a 90° angle along the length of the billet, with the push rod running at a speed of 1-3 mm / s; after each deformation pass, reverse the two ends of the billet along the length direction, and do not rotate the billet along the length direction; do not reheat the billet in the middle of the process.

[0010] Preferably, the magnesium alloy has the following mass percentage composition: Gd: 4.0-9.0%, Y: 2.0-6.0%, Zn: 0.8-2.0%, Zr: 0.2-0.8%, with the remainder being Mg and non-removable impurity elements.

[0011] Preferably, in step B, the annealing process is as follows: after holding at 490-530℃ for 16-50 hours, the annealer is removed and air-cooled.

[0012] Preferably, in step E, the number of equal diameter angular extrusion passes is odd.

[0013] Preferably, in step E, the surface temperature of the billet is 205-305°C after deformation, and then it is air-cooled to room temperature.

[0014] In step E, the room temperature yield strength of the equal diameter angular extruded component along each side length direction is ≥240MPa, tensile strength is ≥300MPa, and elongation after fracture is ≥12.0%, and the absolute value of the strength deviation in different directions is less than 15MPa and the absolute value of the elongation after fracture deviation is less than 2%.

[0015] In the above scheme, the purpose of homogenizing the semi-continuous ingot is to dissolve the eutectic phase as much as possible and remove residual casting stress, thereby improving the plastic forming ability of the ingot. Horizontal forward extrusion with an extrusion ratio of 4-10 on the homogenized annealed ingot yields large-sized alloy bars with oriented LPSO phases and bimodal α-Mg grains, providing billets with specific microstructure characteristics and good formability for subsequent constant-diameter angular extrusion. Setting the length direction of the machined cuboid billet in the extruded bar to be perpendicular to the horizontal forward extrusion direction ensures that the LPSO phase arrangement in the billet is perpendicular to the subsequent constant-diameter angular extrusion direction. This facilitates the elimination of the oriented LPSO phase arrangement caused by horizontal forward extrusion through constant-diameter angular extrusion, reducing the anisotropy caused by the LPSO phase. During constant-diameter angular extrusion, the two ends of the billet along its length are reversed in each deformation pass without rotating the billet along its length direction. This makes the morphology of the LPSO phase and the texture of the α-Mg grains more controllable. Controlling the number of equal diameter angular extrusion passes to an odd number of 5-13 passes aims to further reduce the anisotropy of the mechanical properties of the components.

[0016] The main advantage of this invention is that it proposes a plastic processing technology for quasi-isotropic Mg alloy components. By organically integrating horizontal forward extrusion and constant diameter angular extrusion, and making full use of the process and microstructure control at each stage, high-performance, quasi-isotropic large-size Mg alloy components are successfully produced. The absolute value of the strength deviation in different directions of the components is less than 15 MPa, and the absolute value of the elongation deviation after fracture is less than 2%. Attached Figure Description

[0017] Figure 1 This is a macroscopic photograph of the finished component from Example 1;

[0018] Figure 2 The scanning electron microscope microstructure of the finished component from Example 1;

[0019] Figure 3 This is the EBSD pole figure of the finished component from Example 1;

[0020] Figure 4 These are the stress-strain curves of the finished component from Example 1 subjected to room temperature tension along different side lengths;

[0021] Figure 5 The microstructure of the finished component in Comparative Example 1 is shown by scanning electron microscopy.

[0022] Figure 6 This is the EBSD pole plot of the finished component in Comparative Example 1;

[0023] Figure 7 Scanning electron microscopy microstructure of the finished component in Comparative Example 2

[0024] Figure 8 This is the EBSD pole figure of the finished component in Comparative Example 2. Detailed Implementation

[0025] This invention has been developed through extensive comparative experiments by adjusting plastic processing parameters. Several embodiments are provided below to further illustrate the invention. These embodiments are illustrative and not intended to limit the invention. Any improvements to the process based on the inventive concept fall within the scope of protection of this invention.

[0026] Example 1

[0027] Mg alloy bars with a diameter of Φ430mm were smelted and semi-continuously cast, with the alloy content being Mg-5.3Gd-3.3Y-1.1Zn-0.5Zr by mass percentage. The homogenization annealing process involved holding at 510℃ for 36 hours, followed by air cooling. The homogenized ingot was then cut to obtain round bar billets with a diameter of Φ390mm. These billets and extrusion dies were held at 400℃ for 1 hour, followed by horizontal forward extrusion at an extrusion ratio of 7.1, resulting in bars with a diameter of Φ150mm extruded from the die. The hydraulic rod feed speed was 3mm / s, and the extruded bars were then air-cooled. A rectangular billet with dimensions of 50×50×90mm was machined from extruded bar stock, with its length direction perpendicular to the horizontal forward extrusion direction. The billet was then subjected to equal-diameter angular extrusion in a die with a 90° angle. Before equal-diameter angular extrusion, the billet and die were held at 400℃ for 2 hours. After holding, nine equal-diameter angular extrusion passes were performed along the length of the billet, with the pusher running at a speed of 2mm / s. After each deformation pass, the two ends of the billet along its length were reversed, and the billet did not rotate along its length. The billet was not reheated in the furnace during deformation. After deformation, the surface temperature of the billet was 230℃, and it was then air-cooled to room temperature. Macroscopic photographs of the resulting component are attached. Figure 1 The room temperature tensile mechanical properties of the components along the length (ED) and width (TD1, TD2) directions are listed in Table 1. Scanned images are attached. Figure 2 See attached EBSD pole figure. Figure 3 The tensile stress-strain curves are shown in the appendix. Figure 4 .

[0028] Example 2

[0029] Mg alloy bars with a diameter of Φ330mm were smelted and semi-continuously cast, with the alloy mass percentage content being Mg-9.0Gd-6.0Y-2.0Zn-0.8Zr. The homogenization annealing process involved holding at 530℃ for 16 hours, followed by air cooling. The homogenized ingot was then cut to obtain round bar billets with a diameter of Φ290mm. These billets and extrusion dies were then held at 450℃ for 1 hour, followed by horizontal forward extrusion at an extrusion ratio of 9, resulting in bars with a diameter of Φ100mm extruded from the die. The hydraulic rod feed speed was 0.5mm / s, and the extruded bars were then air-cooled. A rectangular billet with dimensions of 35×35×70mm was machined from extruded bar stock, with the length direction of the billet perpendicular to the horizontal forward extrusion direction. The rectangular billet was subjected to equal-diameter angular extrusion in a die with a 90° included angle. Before equal-diameter angular extrusion, the rectangular billet and die were held at 430℃ for 1 hour. After holding, five equal-diameter angular extrusion passes were performed along the length direction of the billet, with the pusher running at a speed of 1mm / s. After each deformation pass, the two ends of the billet along its length direction were reversed, and the billet was not rotated along its length direction. The billet was not reheated in the furnace during deformation. After deformation, the surface temperature of the billet was 305℃, followed by air cooling to room temperature. The room temperature tensile mechanical properties of the component along its length (ED) and width (TD1, TD2) directions are listed in Table 1.

[0030] Example 3

[0031] Mg alloy bars with a diameter of Φ430mm were smelted and semi-continuously cast, with the alloy content being Mg-4.0Gd-2.0Y-0.8Zn-0.2Zr by mass percentage. The homogenization annealing process involved holding at 490℃ for 50 hours, followed by air cooling. The homogenized ingot was then cut to obtain round bar billets with a diameter of Φ390mm. These billets and extrusion dies were then held at 380℃ for 3 hours, followed by horizontal forward extrusion at an extrusion ratio of 4, resulting in bars with a diameter of Φ200mm extruded from the die. The hydraulic rod feed speed was 3.5mm / s, and the extruded bars were then air-cooled. A rectangular billet with dimensions of 55×55×110mm was machined from extruded bar stock, with the length direction of the billet perpendicular to the horizontal forward extrusion direction. The rectangular billet was subjected to equal-diameter angular extrusion in a die with a 90° included angle. Before equal-diameter angular extrusion, the rectangular billet and die were held at 380℃ for 4 hours. After the holding period, 13 equal-diameter angular extrusion passes were performed along the length direction of the billet, with the pusher running at a speed of 3mm / s. After each deformation pass, the two ends of the billet along its length direction were reversed, and the billet was not rotated along its length direction. The billet was not reheated in the furnace during the deformation process. After deformation, the surface temperature of the billet was 205℃, and it was then air-cooled to room temperature. The room temperature tensile mechanical properties of the component along its length (ED) and width (TD1, TD2) directions are listed in Table 1.

[0032] Comparative Example 1

[0033] Mg alloy bars with a diameter of Φ430mm were smelted and semi-continuously cast, with the alloy content being Mg-5.3Gd-3.3Y-1.1Zn-0.5Zr by mass percentage. The homogenization annealing process involved holding at 510℃ for 36 hours, followed by air cooling. The homogenized ingot was then cut to obtain round bar billets with a diameter of Φ390mm. These billets and extrusion dies were held at 400℃ for 1 hour, followed by horizontal forward extrusion at an extrusion ratio of 7.1, resulting in bars with a diameter of Φ150mm extruded from the die. The hydraulic rod feed speed was 3mm / s, and the extruded bars were then air-cooled. A rectangular billet with dimensions of 50×50×90mm was machined from extruded bar stock, with its length direction perpendicular to the horizontal forward extrusion direction. The billet was subjected to equal-diameter angular extrusion in a die with a 90° angle. Before equal-diameter angular extrusion, the billet and die were held at 350℃ for 2 hours. After holding, 9 passes of equal-diameter angular extrusion were performed along the length direction of the billet, with the pusher running at a speed of 2mm / s. After each pass, the two ends of the billet along its length direction were reversed, and the billet was not rotated along its length direction. The billet was not reheated in the furnace during deformation. After deformation, the surface temperature of the billet was 170℃, followed by air cooling to room temperature. The room temperature tensile mechanical properties of the resulting components along the length (ED) and width (TD1, TD2) directions are listed in Table 1. Scanned images are attached. Figure 5 See attached EBSD pole figure. Figure 6 .

[0034] Comparative Example 2

[0035] Mg alloy bars with a diameter of Φ430mm were smelted and semi-continuously cast, with the alloy content being Mg-5.3Gd-3.3Y-1.1Zn-0.5Zr by mass percentage. The homogenization annealing process involved holding at 510℃ for 36 hours, followed by air cooling. The homogenized ingot was then cut to obtain round bar billets with a diameter of Φ390mm. These billets and extrusion dies were held at 400℃ for 1 hour, followed by horizontal forward extrusion at an extrusion ratio of 7.1, resulting in bars with a diameter of Φ150mm extruded from the die. The hydraulic rod feed speed was 3mm / s, and the extruded bars were then air-cooled. A rectangular billet with dimensions of 50×50×90mm was machined from extruded bar stock, with its length direction parallel to the horizontal forward extrusion direction. The billet was subjected to equal-diameter angular extrusion in a die with a 90° included angle. Before equal-diameter angular extrusion, the billet and die were held at 400℃ for 2 hours. After holding, 9 passes of equal-diameter angular extrusion were performed along the length direction of the billet, with the pusher running at a speed of 2mm / s. After each deformation pass, the two ends of the billet along its length direction were reversed, and the billet was not rotated along its length direction. The billet was not reheated in the furnace during deformation. After deformation, the surface temperature of the billet was 230℃, followed by air cooling to room temperature. The room temperature tensile mechanical properties of the resulting components along the length (ED) and width (TD1, TD2) directions are listed in Table 1. Scanned images are attached. Figure 7 See attached EBSD pole figure. Figure 8 .

[0036] Comparative Example 3

[0037] Mg alloy bars with a diameter of Φ330mm were smelted and semi-continuously cast, with the alloy mass percentage content being Mg-9.0Gd-6.0Y-2.0Zn-0.8Zr. The homogenization annealing process involved holding at 530℃ for 16 hours, followed by air cooling. The homogenized ingot was then cut to obtain round bar billets with a diameter of Φ290mm. These billets and extrusion dies were then held at 450℃ for 1 hour, followed by horizontal forward extrusion at an extrusion ratio of 9, resulting in bars with a diameter of Φ100mm extruded from the die. The hydraulic rod feed speed was 0.5mm / s, and the extruded bars were then air-cooled. A rectangular billet with dimensions of 35×35×70mm was machined from extruded bar stock, with the length direction of the billet perpendicular to the horizontal forward extrusion direction. The rectangular billet was subjected to equal-diameter angular extrusion in a die with a 90° included angle. Before equal-diameter angular extrusion, the rectangular billet and die were held at 430℃ for 1 hour. After holding, the billet underwent 6 passes of equal-diameter angular extrusion along its length, with the pusher running at a speed of 1mm / s. After each deformation pass, the two ends of the billet along its length were reversed, and the billet was not rotated along its length. The billet was not reheated in the furnace during deformation. After deformation, the surface temperature of the billet was 305℃, followed by air cooling to room temperature. The room temperature tensile mechanical properties of the component along its length (ED) and width (TD1, TD2) directions are listed in Table 1.

[0038] Table 1 Mechanical properties of magnesium alloy components in the examples and comparative examples.

[0039]

[0040] from Figure 2 and Figure 3 It can be seen that the finished component in Example 1 exhibits sufficient dynamic recrystallization, and the LPSO phase shows a certain degree of directional alignment. However, the parallelism of the basal plane in the pole figure to the weakly textured component of ED neutralizes the anisotropy that the LPSO phase may cause, ultimately resulting in quasi-isotropy when stretched at room temperature. Figure 4 As shown in Table 1, the room temperature yield strength of the components along each side length direction is ≥240MPa, tensile strength is ≥300MPa, and elongation after fracture is ≥12.0%, with the absolute value of the strength deviation in different directions being less than 15MPa and the absolute value of the elongation after fracture deviation being less than 2%. Table 1 shows that the isotropic mechanical properties of the components in Examples 1, 2, and 3 are significantly better than those in Comparative Examples 1-3.

[0041] Combination Figure 2 , 3 and Figure 5 , 6By comparing Example 1 and Comparative Example 1, the reduced holding temperature of the equal diameter angular extrusion billet and die resulted in insufficient dynamic recrystallization of the component, leading to coarse, strongly textured deformed grains occupying a larger volume fraction. Figure 5 This resulted in a significant increase in texture intensity. Figure 6 The LPSO phase and texture have inconsistent effects on anisotropy, ultimately leading to increased anisotropy in the alloy. The absolute value of the yield strength deviation in different directions reaches 15 MPa, and the absolute value of the elongation deviation after fracture reaches 3%. Meanwhile, comparing Example 1 and Comparative Example 2, in Comparative Example 2, the length direction of the equal-diameter angular extruded billet is parallel to the horizontal forward extrusion direction. Although the dynamic recrystallization of the finished component is sufficient... Figure 7 However, the poles and texture types in the {0001} pole figure change significantly. Figure 8 This process exacerbates the anisotropy of the component, with the absolute value of the yield strength deviation in different directions reaching 19 MPa. Furthermore, by comparing Example 2 and Comparative Example 3, the change from an odd to an even number of equal-diameter angular extrusion passes also alters the microstructure and texture of the component, resulting in severe anisotropy of the mechanical properties of the component in Comparative Example 3. The absolute value of the yield strength deviation in different directions reaches 36 MPa, the absolute value of the ultimate tensile strength deviation reaches 27 MPa, and the absolute value of the elongation after fracture deviation reaches 5.3%.

[0042] The embodiments of the present invention have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention is not limited to the specific embodiments described above; these embodiments are merely illustrative and not limiting. Those skilled in the art, under the guidance of the present invention, can make many modifications without departing from the spirit and scope of the claims, and all such modifications fall within the scope of protection of the present invention.

Claims

1. A plastic processing technology for Mg-Gd-Y-Zn-Zr alloy components, characterized in that... The specific process steps are as follows: A. Smelting and semi-continuous casting Mg-Gd-Y-Zn-Zr alloy rod ingots with diameters of Φ330mm-430mm; B. Perform homogenization annealing on the ingot; C. After homogenization and annealing, the billet is rolled and cut to obtain a bar with a diameter of Φ290mm-390mm. Before extrusion, the bar and the die are kept at 380-450℃ for 1-3 hours. After the heat treatment, the bar is taken out and loaded into the extrusion cylinder for horizontal forward extrusion at an extrusion ratio of 4-9. The extruded bar with a diameter of Φ100-200mm is extruded from the die opening. During horizontal forward extrusion, the hydraulic rod advance speed is 0.5-3.5mm / s. The extruded bar is air-cooled after extrusion. D. Machining a rectangular blank with a cross-sectional side length of 35-55mm and a length of 70-110mm from the extruded bar; the length direction of the rectangular blank is perpendicular to the extrusion direction; E. Extruding the rectangular billet at a 90° angle in a mold; before extruding, heat the rectangular billet and the mold at 380-430℃ for 1-4 hours; after heat treatment, extrude 5-13 times at a 90° angle along the length of the billet, with the push rod running at a speed of 1-3 mm / s; after each deformation pass, reverse the two ends of the billet along the length direction, and do not rotate the billet along the length direction; do not reheat the billet in the middle of the process.

2. The plastic processing technology for a Mg-Gd-Y-Zn-Zr alloy component according to claim 1, characterized in that, The mass percentage composition of the magnesium alloy is Gd: 4.0-9.0%, Y: 2.0-6.0%, Zn: 0.8-2.0%, Zr: 0.2-0.8%, with the remainder being Mg and non-removable impurity elements.

3. The plastic processing technology for a Mg-Gd-Y-Zn-Zr alloy component according to claim 1, characterized in that, In step B, the annealing process is as follows: after holding at 490-530℃ for 16-50 hours, the sample is removed and air-cooled.

4. The plastic processing technology for a Mg-Gd-Y-Zn-Zr alloy component according to claim 1, characterized in that, In step E, the number of equal diameter angular extrusion passes is odd.

5. The plastic processing technology for a Mg-Gd-Y-Zn-Zr alloy component according to claim 1, characterized in that, In step E, after deformation, the surface temperature of the billet is 205-305°C, and then it is air-cooled to room temperature.

6. The plastic processing technology for a Mg-Gd-Y-Zn-Zr alloy component according to claim 1, characterized in that, In step E, the room temperature yield strength of the equal diameter angular extruded component along each side length direction is ≥240MPa, tensile strength is ≥300MPa, and elongation after fracture is ≥12.0%, and the absolute value of the strength deviation in different directions is less than 15MPa and the absolute value of the elongation after fracture deviation is less than 2%.

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