A continuous temperature gradient annealing method for improving the hardness of 5xxx aluminum alloy
Through the continuous temperature gradient annealing method, the heating and cooling rate are controlled, and the problems of reduced hardness and low heat treatment efficiency of 5xxx aluminum alloy are solved, achieving hardness improvement and performance improvement.
Patent Information
- Application Number
- CN202311209178.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-19
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2043-09-19
AI Technical Summary
The hardness of the existing 5xxx aluminum alloy is generally reduced during the heat treatment process, and the uniform annealing process has a long time period and complex process, resulting in low heat treatment efficiency, high heat energy consumption, and prolonging the production cycle.
The continuous temperature gradient annealing method is used to heat to 350-400°C by a heating rate of 1.6-3.3°C/min, and then cool to room temperature at a cooling rate of 5-15°C/min, to control the second phase dissolution and the increase in dislocation density to achieve solid solution strengthening.
In a short time, it significantly improves the hardness of 5xxx aluminum alloy, improves its mechanical properties, simplifies process flow, reduces energy consumption, and shortens production cycles.
Smart Images
Figure CN117070864B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a continuous temperature gradient annealing method for improving the hardness of 5xxx aluminum alloy, belonging to the technical field of heat treatment of aluminum alloy. Background Art
[0002] 5xxx aluminum alloy has good strength and plasticity, electrical conductivity and excellent corrosion resistance, so it is widely used in the shipbuilding industry, aerospace field and information transmission field. This series of alloys belongs to non-heat-treatable strengthening alloys, and it is impossible to improve the structure and mechanical properties of the alloy by aging. Therefore, cold work hardening is mostly used for strengthening during the production process or used in the annealed state. During the heat treatment process of 5xxx aluminum alloy, homogenization annealing is mostly used. The purpose of homogenization annealing is to achieve the uniformity of structure and composition and eliminate stress by maintaining the macroscopic morphology, undergoing phase transformation microscopically, and reconstructing the morphology and distribution state of alloy elements and intermetallic compounds, so as to prevent subsequent processing deformation. The homogenization annealing process is actually a process of phase dissolution and atomic diffusion. Atomic diffusion mainly occurs within the crystal grains, and it can only eliminate the segregation within the crystal grains and has little effect on regional segregation. Homogenization annealing includes single-stage homogenization and two-stage homogenization. The strengthening effect of two-stage homogenization is significantly better than that of single-stage homogenization. However, for alloys with more complex compositions, even if the holding time of homogenization is very long, it is difficult to achieve satisfactory results, which reduces the efficiency of the heat treatment process, increases heat energy consumption, prolongs the production cycle, and is not conducive to environmental protection. Summary of the Invention
[0003] Aiming at the problems in the existing annealing process that the hardness of 5xxx aluminum alloy generally decreases, the homogenization annealing process has a long time cycle and complex process, which reduces the efficiency of the heat treatment process, increases heat energy consumption, and prolongs the production cycle, etc., the present invention proposes a continuous temperature gradient annealing method for improving the hardness of 5xxx aluminum alloy. By increasing the dislocation density of some crystal planes in 5xxx aluminum alloy and solid solution strengthening of the alloy, the hardness of 5xxx aluminum alloy is improved. Compared with the existing annealing process, the present invention can improve the hardness of 5xxx aluminum alloy through a more concise process flow in a shorter time. Adopting a reasonable continuous temperature gradient annealing process can improve the mechanical properties of 5xxx aluminum alloy.
[0004] A continuous temperature gradient annealing method for improving the hardness of 5xxx aluminum alloy, the specific steps are as follows:
[0005] (1) Heat the 5xxx aluminum alloy at a heating rate of 1.6 - 3.3 °C / min uniformly to a temperature of 350 - 400 °C for continuous temperature gradient annealing;
[0006] (2) Cool the 5xxx aluminum alloy after continuous temperature gradient annealing in step (1) uniformly to room temperature at a cooling rate of 5 - 15 °C / min.
[0007] The heating time of the step (1) is 2 to 3 h.
[0008] Principle of the continuous temperature gradient annealing process for improving the hardness of 5xxx aluminum alloy in the present invention:
[0009] Heat at a uniform heating rate of 1.6 to 3.3 °C / min to a temperature of 350 to 400 °C for continuous temperature gradient annealing, so that the second phase of the 5xxx aluminum alloy dissolves at different temperatures, control the cooling rate at 5 to 15 °C / min to reduce the precipitation of the second phase, enhance the solid solution strengthening effect, and after continuous temperature gradient annealing, the dislocation density of some crystal planes increases, improving the mechanical properties of the alloy to a certain extent and enhancing the hardness of the 5xxx aluminum alloy.
[0010] The beneficial effects of the present invention are:
[0011] (1) The present invention enhances the hardness of 5xxx aluminum alloy through the solid solution strengthening of 5xxx aluminum alloy and the increase in the dislocation density of some crystal planes in the alloy;
[0012] (2) Compared with the recrystallization annealing and homogenization annealing adopted by the existing heat treatment methods, the present invention can improve the hardness of 5xxx aluminum alloy through a more concise process flow in a shorter time, and the mechanical properties of 5xxx aluminum alloy can be improved by adopting a reasonable continuous temperature gradient annealing process. Description of the drawings
[0013] Figure 1 It is the continuous temperature gradient annealing process diagram of 5xxx aluminum alloy;
[0014] Figure 2 It is the isothermal annealing process diagram of 5xxx aluminum alloy for Comparative Examples 1 to 3;
[0015] Figure 3 It is the comparison diagram of the microhardness of the aluminum alloy for Examples 1 to 3 and Comparative Examples 1 to 3;
[0016] Figure 4 It is the SEM diagram of the structure of 5xxx aluminum alloy after annealing in Example 2;
[0017] Figure 5 It is the SEM diagram of the structure of 5xxx aluminum alloy after annealing in Comparative Example 2. Specific embodiments
[0018] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the content described.
[0019] In the embodiments of the present invention, the composition of the 5xxx aluminum alloy is within the standard composition range specified in GB-T3190-2020. The microhardness of the aluminum alloy structure is detected using a 3S-1000QZD digital Vickers hardness tester (F = 0.2 Kg, t = 15 s). Seven points are measured for each specimen, and after removing the highest and lowest points, the average value of the remaining five measurement data is taken.
[0020] Comparative Example 1: Isothermal annealing method for 5xxx aluminum alloy (see Figure 2 ), and the specific steps are as follows:
[0021] (1) The 5xxx aluminum alloy is heated at a uniform heating rate of 20 °C / min to a temperature of 360 °C and held for 2 h for isothermal annealing treatment;
[0022] (2) The 5xxx aluminum alloy subjected to isothermal annealing treatment is cooled at a uniform cooling rate of 5 °C / min to room temperature;
[0023] The microhardness of the aluminum alloy after heat treatment in this comparative example is 66.6 HV (see Figure 3 ).
[0024] Example 1: A continuous temperature gradient annealing method for improving the hardness of 5xxx aluminum alloy (see Figure 1 ), and the specific steps are as follows:
[0025] (1) The 5xxx aluminum alloy is heated at a uniform heating rate of 3.0 °C / min for 2 h to a temperature of 360 °C for continuous temperature gradient annealing, so that the second phase of the 5xxx aluminum alloy is dissolved at different temperatures during the continuous heating process. At the same time, the dislocation density increases during the heating process, improving the mechanical properties of the 5xxx aluminum alloy and enhancing the hardness of the 5xxx aluminum alloy;
[0026] (2) The 5xxx aluminum alloy after continuous temperature gradient annealing in step (1) is cooled at a uniform cooling rate of 5 °C / min to room temperature, and the cooling rate of 5 °C / min is controlled to reduce the precipitation of the second phase and enhance the solid solution strengthening effect;
[0027] The microhardness of the 5xxx aluminum alloy after heat treatment in this example is 78.9 HV (see Figure 3 ). Compared with the 5xxx aluminum alloy after heat treatment in Comparative Example 1, its microhardness is increased by 12.3 HV.
[0028] Comparative Example 2: Isothermal annealing method for 5xxx aluminum alloy (see Figure 2 ), and the specific steps are as follows:
[0029] (1) The 5xxx aluminum alloy is heated at a uniform heating rate of 20 °C / min to a temperature of 380 °C and held for 2.5 h for isothermal annealing treatment;
[0030] (2) Cool the isothermally annealed 5xxx aluminum alloy at a uniform cooling rate of 8 °C / min to room temperature;
[0031] The microhardness of the aluminum alloy after heat treatment in this comparative example is 63.3 HV (see Figure 3 ).
[0032] Example 2: A continuous temperature gradient annealing method for improving the hardness of 5xxx aluminum alloy (see Figure 1 ), the specific steps are as follows:
[0033] (1) Heat the 5xxx aluminum alloy at a uniform heating rate of 2.53 °C / min for 2.5 h to a temperature of 380 °C for continuous temperature gradient annealing, so that the 5xxx aluminum alloy dissolves the second phase at different temperatures during the continuous heating process. At the same time, the dislocation density increases during the heating process, improving the mechanical properties of the 5xxx aluminum alloy and enhancing the hardness of the 5xxx aluminum alloy;
[0034] (2) Cool the 5xxx aluminum alloy after continuous temperature gradient annealing in step (1) at a uniform cooling rate of 8 °C / min to room temperature, and control the cooling rate of 8 °C / min to reduce the precipitation of the second phase and enhance the solid solution strengthening effect;
[0035] The microhardness of the 5xxx aluminum alloy after heat treatment in this example is 81.3 HV (see Figure 3 ). Compared with the 5xxx aluminum alloy after heat treatment in Comparative Example 2, its microhardness is increased by 18 HV;
[0036] The SEM image of the microstructure of the 5xxx aluminum alloy after heat treatment in Comparative Example 2 is shown in Figure 4 , and the 5xxx aluminum alloy after heat treatment in Example 2 of this example is shown in Figure 5 . Analysis shows that the irregular granular second phase discontinuously distributed in the alloy is mainly β phase (Mg2Al3), Figure 4 The shown coarse β phase is not significantly refined; there are more β phases in the grains, so there is no obvious dispersion strengthening and solid solution strengthening effect, resulting in low hardness; while Figure 5 The shown second phase β phase is significantly refined and partially redissolved in the matrix, achieving the solid solution strengthening effect and eliminating the inhomogeneity of composition and microstructure.
[0037] Comparative Example 3: Isothermal annealing method for 5xxx aluminum alloy (see Figure 2 ), the specific steps are as follows:
[0038] (1) Heat the 5xxx aluminum alloy at a uniform heating rate of 20 °C / min to a temperature of 400 °C and hold for 2 h for isothermal annealing treatment;
[0039] (2) The isothermally annealed 5xxx aluminum alloy was cooled uniformly to room temperature at a cooling rate of 15 °C / min;
[0040] The microhardness of the aluminum alloy after heat treatment in this comparative example was 63.7 HV (see Figure 3 ).
[0041] Example 3: A continuous temperature gradient annealing method for improving the hardness of 5xxx aluminum alloy (see Figure 1 ), the specific steps are as follows:
[0042] (1) The 5xxx aluminum alloy was heated uniformly at a heating rate of 3.3 °C / min for 2 h to a temperature of 400 °C for continuous temperature gradient annealing, so that the second phase of the 5xxx aluminum alloy was dissolved at different temperatures during the continuous heating process. At the same time, the dislocation density increased during the heating process, improving the mechanical properties of the 5xxx aluminum alloy and enhancing the hardness of the 5xxx aluminum alloy;
[0043] (2) The 5xxx aluminum alloy after continuous temperature gradient annealing in step (1) was cooled uniformly to room temperature at a cooling rate of 15 °C / min, and the cooling rate of 15 °C / min was controlled to reduce the precipitation of the second phase and enhance the solid solution strengthening effect;
[0044] The microhardness of the 5xxx aluminum alloy after heat treatment in this example was 79.1 HV (see Figure 3 ). Compared with the 5xxx aluminum alloy after heat treatment in Comparative Example 2, its microhardness increased by 15.4 HV.
[0045] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.
Claims
1. A continuous temperature gradient annealing method for improving the hardness of 5xxx aluminum alloy, characterized in that, The specific steps are as follows: (1) Heat the 5xxx aluminum alloy at a uniform heating rate of 1.6 - 3.3 °C / min to a temperature of 350 - 400 °C for continuous temperature gradient annealing, so that the second phase of the 5xxx aluminum alloy dissolves at different temperatures during the continuous heating process. At the same time, the dislocation density increases during the heating process, enhancing the hardness of the 5xxx aluminum alloy; (2) Cool the 5xxx aluminum alloy annealed by continuous temperature gradient in step (1) to room temperature at a uniform cooling rate of 5 - 15 °C / min, and control the cooling rate of 5 - 15 °C / min to reduce the precipitation of the second phase and enhance the solid solution strengthening effect.
2. The continuous temperature gradient annealing method for improving the hardness of 5xxx aluminum alloy according to claim 1, characterized in that: The heating time in step (1) is 2 - 3 h.