A secondary extrusion molding process for rare earth magnesium alloy bars

Abstract

The invention discloses a secondary extrusion forming process of a rare earth magnesium alloy bar, relates to the field of non-ferrous metal materials and their processing technology, and specifically includes the following steps: homogenization treatment, primary extrusion forming, short-time solid solution treatment, secondary extrusion forming, and isothermal aging treatment. A short-time solid solution treatment is performed between the primary extrusion and the secondary extrusion, the temperature of the solid solution treatment is 490°C to 530°C, the time is 20min to 5h, and the solid solution is quenched in cold water after completion. After that, the secondary extrusion is performed, the extrusion temperature is 260 to 320°C, the extrusion ratio is 7 to 16, and the extrusion speed is 0.3 to 0.4 mm / s. The secondary extrusion process in the present invention can further refine the grains on the basis of the primary extrusion, thereby effectively improving the performance of the magnesium alloy. The short-time solid solution treatment after the primary extrusion and before the secondary extrusion can not only make the secondary extrusion easier to perform, but also make the dynamic precipitation in the primary extrusion process re-dissolve, thereby further improving the mechanical properties of the alloy after the secondary extrusion.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal structural material processing, and in particular relates to a secondary extrusion process for rare earth magnesium alloy bars. Background Art

[0002] Magnesium alloy is the lightest metal structural material, and also has the advantages of high specific strength and specific stiffness, superior damping performance, good biocompatibility, large hydrogen storage capacity, and high theoretical specific capacity of batteries. Therefore, magnesium and its alloys are widely used in aerospace, automobile, 3C (computer, communication and consumer electronics) and other fields. However, the lower strength and poor plasticity greatly limit the application scope of magnesium alloys.

[0003] Plastic processing such as extrusion, rolling and forging is currently a widely used method for strengthening and toughening magnesium alloys. Extrusion has a stronger three-dimensional compressive stress state than forging and rolling, and the metal can exert its maximum plasticity, which is especially important for magnesium alloys with poor plastic deformation ability. In addition, dynamic recrystallization is very easy to occur during the extrusion process, forming fine recrystallized grains. At the same time, the overall grain structure will preferentially present a fixed arrangement in certain directions, and a large number of dynamic precipitation phases will precipitate inside the grains or on the grain boundaries. In addition, the subgrain structure and dislocation density inside the deformed grains will increase during the extrusion process.

[0004] All of the above factors will strengthen magnesium alloys in various aspects, but the effect of one extrusion on grain refinement is often limited. Secondary extrusion based on the first extrusion can further refine the grains, which is expected to improve the strength and plasticity of magnesium alloys at the same time. If a second extrusion is performed directly after the first extrusion, the extrusion tonnage will be too high, increasing the difficulty of extrusion. In addition, the dynamic precipitation precipitated during the first extrusion will promote recrystallization nucleation during the second extrusion, increase the degree of recrystallization of the alloy, and thus reduce the strength of the alloy.

[0005] In addition, the dynamic precipitation precipitated in the first extrusion will consume the solute atoms in the matrix, resulting in a weakening of the subsequent aging strengthening effect. In order to solve these problems, a short-term solid solution treatment can be performed before the second extrusion to make the second phase precipitated in the first extrusion process dissolve back into the matrix, thereby better exerting the effect of the second extrusion. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a secondary extrusion process, which can further refine the grains of the alloy on the basis of the primary extrusion, thereby obtaining good strength and plasticity. The short-term solution treatment between the primary extrusion and the secondary extrusion can reduce the difficulty of the secondary extrusion and play a role in regulating performance.

[0007] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows.

[0008] The present invention provides a secondary extrusion molding process for a rare earth magnesium alloy bar, comprising the following steps: (a) homogenizing a target rare earth magnesium alloy ingot;

[0009] (b) subjecting the homogenized alloy to a primary extrusion molding to obtain a primary extruded rod;

[0010] (c) performing a short-term solid solution treatment on the alloy after the first extrusion;

[0011] (d), then performing secondary extrusion molding to obtain a secondary extruded rod;

[0012] (e) Finally, the secondary extruded rod is subjected to isothermal aging treatment.

[0013] Further improvement and optimization of the above technical solution, in the step (b), the extrusion temperature of the first extrusion is 400°C to 500°C, the extrusion ratio is 4 to 8, and the extrusion speed is 0.3 to 1.2 mm / s.

[0014] Further improvement and optimization of the above technical solution, in the step (c), the short-time solution temperature is 500°C to 520°C, the time is 20min to 5h, and after the solution is completed, it is quenched in cold water.

[0015] Further improvement and optimization of the above technical solution, in step (d), the extrusion temperature of the secondary extrusion is 280-320°C, the extrusion ratio is 7-16, the extrusion speed is 0.3-0.4 mm / s, and after extrusion, it is quenched in cold water.

[0016] Further improvement and optimization of the above technical solution, the temperature of the isothermal aging treatment in step (e) is 200°C and the insulation time is 0 to 20 hours.

[0017] Further improvement and optimization of the above technical solution: take Mg-17Gd-0.3Zr (wt.%) ingot, homogenize it at 510℃ for 15h, and immediately put it into warm water at 60-100℃ for quenching after solution treatment; keep the homogenized ingot at 500℃ for 15-25min and then put it into the extrusion barrel for extrusion, and preheat the extrusion barrel to 400℃ before extrusion; extrusion is carried out at a speed of 0.3-0.4mm / s, and the extrusion ratio is 4, After extrusion, the rod is quenched in cold water to obtain a primary extruded rod; then the primary extruded rod is placed in a heat treatment furnace, short-term solid solution is performed at 500°C for 20 to 30 minutes, and then quickly taken out and quenched in cold water; next, the alloy is kept at 320°C for 13 minutes and then put into an extrusion barrel preheated to the same temperature for extrusion to obtain an extruded rod with a diameter of 18 mm, an extrusion speed of 0.3 to 0.4 mm / s, an extrusion ratio of 7, and is quickly quenched in cold water after extrusion.

[0018] Further improvement and optimization of the above technical solution, taking a Mg-1.0Mn-0.4Ca-0.2Ce (wt.%) ingot, homogenizing it and then extruding it once; extruding an alloy ingot with a diameter of 500 mm at an extrusion temperature of 400°C, an extrusion speed of 0.8-1.2 mm / s, to obtain an alloy rod with a diameter of 180 mm; short-term solid solution of the alloy at 520°C for 5 hours, then cutting to obtain an extruded ingot with a diameter of 80 mm, and performing a secondary extrusion at 280°C-320°C to obtain a rod with a diameter of 20 mm, an extrusion speed of 0.3-0.4 mm / s, an extrusion ratio of 16, and quenching in cold water after extrusion.

[0019] Further improvement and optimization of the above technical solution, taking Mg-1.5Mn-0.2Ce (wt.%) ingot, homogenizing it and then performing a first extrusion molding; extruding an alloy ingot with a diameter of 500mm at an extrusion temperature of 400℃, and an extrusion speed of 0.8-1.2mm / s to obtain an alloy rod with a diameter of 180mm; short-term solid solution of the alloy at 520℃ for 5h, and then cutting to obtain an extruded ingot with a diameter of 80mm, and performing a second extrusion at 280℃-320℃ to obtain a rod with a diameter of 20mm, the extrusion speed is 0.3-0.4mm / s, the extrusion ratio is 16, and after extrusion, it is quenched in cold water.

[0020] The beneficial effects obtained by the technical solution of the present invention are:

[0021] The present invention can further refine the grains of the alloy on the basis of the primary extrusion through the secondary extrusion process, thereby obtaining good strength and plasticity. And it is particularly important to perform a short-time solution treatment before the secondary extrusion. On the one hand, the short-time solution treatment can reduce the density of defects such as dislocations inside the alloy, improve the degree of recrystallization, and make the secondary extrusion easier to perform. On the other hand, for rare earth magnesium alloys with obvious aging hardening response, during the short-time solution treatment process, the second phase precipitated in the primary extrusion can be dissolved back into the matrix, so that more aging phases can be precipitated in the subsequent aging process, and better aging strengthening effect can be obtained. In addition, since the dynamic precipitation of the primary extrusion will promote the recrystallization nucleation during the secondary extrusion process, the degree of recrystallization of the alloy after the secondary extrusion can also be regulated by regulating the time of the short-time solution treatment, thereby achieving the purpose of regulating performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the metallographic structure of the rare earth magnesium alloy rod prepared in Example 2 of the present invention.

[0023] Figure 2 This is the stress-strain curve of the rare earth magnesium alloy rod prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0024] Example 1

[0025] Take the Mg-17Gd-0.3Zr (wt.%) ingot, homogenize it at 510℃ for 15h, and immediately put it into warm water at 60-100℃ for quenching after the solution treatment. Keep the homogenized ingot at 500℃ for 15-25min and put it into the extrusion barrel for extrusion. Before that, preheat the extrusion barrel to 400℃. Extrusion is carried out at a speed of 0.3-0.4mm / s, and the extrusion ratio is 4. After extrusion, put it into cold water for quenching to obtain a primary extruded rod. Then put the primary extruded rod into the heat treatment furnace, short-term solid solution at 500℃ for 20min, then quickly take it out and put it into cold water for quenching. Next, keep the alloy at 320℃ for 13min and put it into the extrusion barrel preheated to the same temperature for extrusion to obtain an extruded rod with a diameter of 18mm. The extrusion speed is 0.3-0.4mm / s, the extrusion ratio is 7, and it is quickly put into cold water for quenching after extrusion. Finally, isothermal aging was carried out at 200 °C for 20 h.

[0026] According to the standard of GBT-228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the alloy prepared in Example 1 of the present invention was tested for room temperature mechanical properties. The tensile direction was parallel to the extrusion direction. The test results are listed in Table 1.

[0027] Example 2

[0028] Take the Mg-17Gd-0.3Zr (wt.%) ingot, homogenize it at 510℃ for 15h, and immediately put it into warm water at 60-100℃ for quenching after the solution treatment. After homogenization, keep it at 500℃ for 15-25min and then put it into the extrusion barrel preheated to 400℃ for extrusion. Extrusion is carried out at a speed of 0.3-0.4mm / s, the extrusion ratio is 4, and it is quenched in cold water after extrusion. Then put the alloy into the heat treatment furnace, short-term solid solution at 500℃ for 30min, and quickly take it out and put it into cold water for quenching after the solid solution is completed. Next, keep the alloy at 320℃ for 13min and then put it into the extrusion barrel preheated to the same temperature for extrusion to obtain an extruded rod with a diameter of 18mm. The extrusion speed is 0.3-0.4mm / s, the extrusion ratio is 7, and it is quickly quenched in cold water after extrusion. Finally, isothermal aging is carried out at 200℃ for 20h.

[0029] According to the standard of GBT-228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the alloy prepared in Example 2 of the present invention was tested for room temperature mechanical properties. The tensile direction was parallel to the extrusion direction. The test results are listed in Table 1.

[0030] Example 3

[0031] Take Mg-1.0Mn-0.4Ca-0.2Ce (wt.%) ingot, homogenize it and perform a first extrusion. Extrude the alloy ingot with a diameter of 500mm at an extrusion temperature of 400℃, and the extrusion speed is 0.8-1.2mm / s to obtain an alloy rod with a diameter of 180mm. The alloy is short-term solid solution at 520℃ for 5h, and then cut to obtain an extruded ingot with a diameter of 80mm, and then extruded twice at 280℃ to obtain a rod with a diameter of 20mm, the extrusion speed is 0.3-0.4mm / s, the extrusion ratio is 16, and quenched in cold water after extrusion.

[0032] According to the standard of GBT-228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the alloy prepared in Example 3 of the present invention was tested for room temperature mechanical properties. The tensile direction was parallel to the extrusion direction. The test results are listed in Table 1.

[0033] Example 4

[0034] Take Mg-1.0Mn-0.4Ca-0.2Ce (wt.%) ingot, homogenize it and perform a first extrusion. Extrude the alloy ingot with a diameter of 500mm at an extrusion temperature of 400℃, and the extrusion speed is 0.8-1.2mm / s to obtain an alloy rod with a diameter of 180mm. The alloy is short-term solid solution at 520℃ for 5h, and then cut to obtain an extruded ingot with a diameter of 80mm, and then extruded twice at 320℃ to obtain a rod with a diameter of 20mm, the extrusion speed is 0.3-0.4mm / s, the extrusion ratio is 16, and quenched in cold water after extrusion.

[0035] According to the standard of GBT-228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the alloy prepared in Example 4 of the present invention was tested for room temperature mechanical properties. The tensile direction was parallel to the extrusion direction. The test results are listed in Table 1.

[0036] Example 5

[0037] Take Mg-1.5Mn-0.2Ce (wt.%) ingot, homogenize it and then perform extrusion molding. Extrude the alloy ingot with a diameter of 500mm at an extrusion temperature of 400℃, and the extrusion speed is 0.8-1.2mm / s to obtain an alloy rod with a diameter of 180mm. The alloy is short-term solid solution at 520℃ for 5h, and then cut to obtain an extruded ingot with a diameter of 80mm, and then perform secondary extrusion at 280℃ to obtain a rod with a diameter of 20mm, the extrusion speed is 0.3-0.4mm / s, the extrusion ratio is 16, and quenched in cold water after extrusion.

[0038] According to the standard of GBT-228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the alloy prepared in Example 5 of the present invention was tested for room temperature mechanical properties. The tensile direction was parallel to the extrusion direction. The test results are listed in Table 1.

[0039] Example 6

[0040] Take Mg-1.5Mn-0.2Ce (wt.%) ingot, homogenize it and then perform extrusion molding. Extrude the alloy ingot with a diameter of 500mm at an extrusion temperature of 400℃, and the extrusion speed is 0.8-1.2mm / s to obtain an alloy rod with a diameter of 180mm. The alloy is short-term solid solution at 520℃ for 5h, and then cut to obtain an extruded ingot with a diameter of 80mm, and then perform secondary extrusion at 320℃ to obtain a rod with a diameter of 20mm, the extrusion speed is 0.3-0.4mm / s, the extrusion ratio is 16, and quenched in cold water after extrusion.

[0041] According to the standard of GBT-228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the alloy prepared in Example 6 of the present invention was tested for room temperature mechanical properties. The tensile direction was parallel to the extrusion direction. The test results are listed in Table 1.

[0042] The above is an implementation scheme of the present invention. It should be pointed out that for ordinary technicians in this technical field, several modifications and improvements can be made without departing from the principles and core ideas of the patent of the present invention. These modifications and improvements are also considered to be within the scope of protection of the patent of the present invention.

[0043]

[0044] Table 1. Room temperature mechanical properties of the alloys prepared in Examples 1 to 6 in the extrusion direction.

Claims

1. A secondary extrusion molding process for a rare earth magnesium alloy bar, the steps of which are as follows: (a) taking a Mg-17Gd-0.3Zr (wt.%) ingot and homogenizing the target rare earth magnesium alloy ingot; (b) Extruding the homogenized alloy once to obtain a primary extruded rod; the primary extrusion temperature is 500°C, the extrusion ratio is 4, and the extrusion speed is 0.3-0.4 mm / s; (c) The alloy after the first extrusion is subjected to a short-time solid solution treatment; the short-time solid solution temperature is 500°C, the time is 20 min to 30 min, and after the solid solution is completed, it is quenched in cold water; (d) Then, secondary extrusion molding is performed to obtain secondary extruded rods; the extrusion temperature of the secondary extrusion is 320°C, the extrusion ratio is 7, the extrusion speed is 0.3-0.4 mm / s, and after extrusion, the rods are quenched in cold water; (e) Finally, the secondary extruded rod is subjected to isothermal aging treatment; the isothermal aging treatment temperature is 200°C and the holding time is 20 h.

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