Process for improving the hardness of 5A06 aluminum-magnesium alloy

Abstract

The application discloses a process method for improving the hardness of 5A06 aluminum magnesium alloy, and comprises the following steps: step 1, cutting processing is performed on the 5A06 aluminum alloy rod to form a plurality of cylindrical short samples; step 2, the sample is subjected to deformation treatment: the sample is compressed once, and the deformation amount is 16%-32%; step 3, the sample subjected to the deformation treatment is directly immersed in liquid nitrogen for cryogenic treatment, is placed in air to be warmed to room temperature, and the hardness of the sample is measured. The application solves the problems that it is difficult to improve the hardness of the aluminum magnesium alloy and difficult to prolong the service life at present, the cryogenic treatment time has a significant influence on the structure of the 5A06 aluminum alloy, the number of Al3Mg2 phases in the structure is obviously increased with the prolonging of the cryogenic treatment time, the hardness of the alloy can be further improved by adopting the process of deformation superposition and cryogenic treatment, so that the wear resistance is improved, and the service life of the alloy is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of alloy materials technology, specifically relating to a process method for improving the hardness of 5A06 aluminum-magnesium alloy. Background Technology

[0002] Aluminum-magnesium alloys are non-heat-treatable aluminum alloys, and their age-hardening effect is not significant. Therefore, strengthening aluminum-magnesium alloys can only be achieved through cold work hardening, stabilizing annealing, and increasing the magnesium content. In the aerospace industry, 5A06 aluminum alloy is often used to manufacture aircraft engines, propellers, brackets, and other components. In the automotive industry, aluminum-magnesium alloys are commonly used to manufacture cylinder heads, engine covers, and other components. In the electronics industry, aluminum-magnesium alloys are frequently used as materials for manufacturing 3C products due to their excellent heat dissipation, impact resistance, and other properties.

[0003] Given the wide range of applications and high consumption of aluminum-magnesium alloys, further extending their service life, conserving materials, and achieving high-quality development are of great significance. It is well known that the higher the hardness of an alloy material, the better its wear resistance and the longer its service life. The hardness of 5A06 aluminum alloy is already quite high, and it is difficult to increase its hardness using conventional heat treatment processes. Summary of the Invention

[0004] The purpose of this invention is to provide a process method for improving the hardness of 5A06 aluminum-magnesium alloy, which solves the current problems of difficulty in improving the hardness of aluminum-magnesium alloy and difficulty in extending its service life.

[0005] To achieve the above-mentioned technical objectives, the present invention specifically employs the following technical solutions:

[0006] A process for improving the hardness of 5A06 aluminum-magnesium alloy includes the following steps:

[0007] Step 1: Machining the 5A06 aluminum alloy bar to produce several cylindrical short samples.

[0008] Step 2: Deform the sample: Compress the sample once, with deformation ranging from 16% to 32%.

[0009] Step 3: Immerse the deformed sample directly in liquid nitrogen for cryogenic treatment, then place it in air to warm to room temperature, and measure the hardness of the sample.

[0010] Furthermore, the cylindrical short sample has a diameter of 15 mm and a height of 25 mm.

[0011] Furthermore, the deformation amounts were 16%, 24%, and 32%.

[0012] Furthermore, the cryogenic treatment time is 72 hours.

[0013] The beneficial effects of this invention are:

[0014] (1) When 5A06 aluminum alloy is cryogenically treated directly without deformation, the alloy hardness decreases instead of increasing. When cryogenically treated after deformation, the alloy hardness increases with the extension of cryogenic treatment time.

[0015] (2) The best process to improve the hardness of 5A06 aluminum alloy is to deform by 16% + cryogenic treatment for 72 hours.

[0016] (3) When the deformation amount is the same, the cryogenic treatment time has a significant impact on the microstructure of 5A06 aluminum alloy. With the extension of the cryogenic treatment time, the amount of Al3Mg2 phase in the microstructure increases significantly. The process of deformation superimposed with cryogenic treatment can further improve the hardness of the alloy, thereby improving wear resistance and extending the service life of the alloy. Attached Figure Description

[0017] Figure 1 The SEM structure of the 5A06 aluminum alloy of this invention after different processing techniques is shown. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1

[0020] The material used in this invention is 5A06 aluminum alloy rod, the composition of which is shown in Table 1.

[0021] Table 1 Chemical composition of 5A06 aluminum alloy (mass fraction / %)

[0022]

[0023] 5A06 aluminum alloy bars were machined to prepare several standard compression specimens. Each standard compression specimen was a short cylindrical bar, 15 mm in diameter and 25 mm in height. A hydraulic universal testing machine was used to perform a single compression test on the standard compression specimens to achieve deformation. The deformation amounts of the standard compression specimens were 16%, 24%, and 32%, respectively.

[0024] First, the 5A06 aluminum alloy samples were deformed to 16%, 24%, and 32% deformation. Then, standard compression samples with deformations of 16%, 24%, and 32% were subjected to cryogenic treatment. These standard compression samples were directly immersed in liquid nitrogen for the specified holding time, then removed and cooled using liquid nitrogen as the cooling medium. As shown in Table 2, the holding time was 24 hours, after which the samples were allowed to warm to room temperature in air.

[0025] Comparative Example 1

[0026] The experimental material was 5A06 aluminum alloy bar, the composition of which is shown in Table 1. Undeformed 5A06 aluminum alloy samples underwent cryogenic treatment, as shown in Table 2, with cryogenic treatment times of 0h, 24h, and 72h.

[0027] Example 2

[0028] The experimental material was 5A06 aluminum alloy rod, the composition of which is shown in Table 1. As shown in Table 2, the 5A06 aluminum alloy samples were first deformed, with deformation amounts of 16%, 24%, and 32%, respectively. Then, they underwent cryogenic treatment. The standard compression samples were directly immersed in liquid nitrogen for the specified holding time, and then removed, using liquid nitrogen as the cooling medium. The holding time was 72 hours, after which the samples were allowed to warm to room temperature in air.

[0029] Two standard compression specimens were obtained from the processing methods of Example 1, Example 2 and Comparative Example 1. One standard compression specimen was used for hardness testing and the other standard compression specimen was used for tissue analysis.

[0030] Hardness test experiment

[0031] Hardness testing was conducted using a 210HBS-3000 digital display Brinell hardness tester with a φ10mm quenched steel ball indenter, a test load of 1000kgf, and a holding time of 30s.

[0032] The hardness test specimen number, metallographic test number, specific treatment process, and hardness results are shown in Table 2.

[0033] Table 2. Hardness of 5A06 aluminum alloy samples after different deformation and cryogenic treatment times.

[0034]

[0035]

[0036] Hardness test results

[0037] Table 2 shows the Brinell hardness test results of 5A06 aluminum alloy samples after untreated, cryogenic treatment, and deformation-enhanced cryogenic treatment. As can be seen from Table 2, sample number 1 underwent no treatment, while samples number 2 and 3 underwent cryogenic treatment directly without deformation. Compared with sample number 1, the hardness of samples number 2 and 3 decreased slightly. This indicates that cryogenic treatment alone did not improve the hardness of the 5A06 aluminum alloy samples. The hardness of the 5A06 aluminum alloy samples decreased after cryogenic treatment without deformation. This is because 5A06 aluminum alloy is a hot-extruded profile with a heat treatment state of H112. Furthermore, it underwent machining during sample preparation, resulting in residual stress in the samples. Studies have shown that cryogenic treatment can eliminate residual stress in metallic materials. Therefore, the work hardening of the alloy samples was weakened after cryogenic treatment, leading to a decrease in hardness.

[0038] As the cryogenic treatment time increased, the decrease in hardness rebounded somewhat. Cryogenic treatment can improve the strength and hardness of aluminum alloy materials; therefore, the hardness of the samples will increase with the extension of the cryogenic treatment time. The experimental results of hardness samples No. 2 and No. 3 in Table 2 confirm this. It can be seen that if the 5A06 aluminum alloy is not deformed, the effect of cryogenic treatment on its hardness is relatively small.

[0039] Table 2 also shows that the hardness of the 5A06 aluminum alloy samples significantly increased after deformation and deep cryogenic treatment. Of course, work hardening contributes to this increase in hardness. Further investigation revealed that deep cryogenic treatment does indeed affect the hardness of the deformed 5A06 aluminum alloy samples. Comparing samples 4 and 7, both with a deformation amount of 16%, the hardness increased from 101.2 HB to 103.5 HB after 24 and 72 hours of deep cryogenic treatment. Similarly, comparing samples 5 and 8, and samples 6 and 9, with deformation amounts of 24% and 32% respectively, the hardness of all samples increased to varying degrees after 24 and 72 hours of deep cryogenic treatment. The most significant effect of deep cryogenic treatment on hardness was observed in the sample with a deformation amount of 16%, followed by samples with deformation amounts of 32% and 24%. This demonstrates that, with the same deformation amount, the hardness of the samples increases with the extension of the deep cryogenic time.

[0040] Metallographic structure of samples treated with different composite processes

[0041] Metallographic sample preparation: After pre-grinding and polishing, the samples were etched with hydrofluoric acid aqueous solution. Microstructure analysis was performed using a scanning electron microscope.

[0042] The scanning electron microscope (SEM) microstructure of the 5A06 aluminum alloy sample after different processing steps is as follows: Figure 1 As shown. From Figure 1It is evident that the SEM microstructure of the undeformed specimens, both untreated and after 24-hour cryogenic treatment, showed no significant changes. Figure 1 (a) and (b), but after 72 hours of cryogenic treatment, the amount of granular Al3Mg2 phase in the sample microstructure increased and the distribution became more uniform, see (a) and (b). Figure 1 (c). This is consistent with the results of the hardness test.

[0043] In Table 2, the three metallographic specimens, numbered d, e, and f, all underwent the same cryogenic treatment for 24 hours, with deformation increasing sequentially to 16%, 24%, and 32%, respectively. It is clearly evident that... Figure 1 The Al3Mg2 phase is the most abundant in the (d) tissue. Figure 1 (f) is the second, Figure 1 The value of (e) is the lowest. With increasing deformation, work hardening intensifies, residual stress increases, and the effect of cryogenic treatment in eliminating residual stress increases, while its effect in refining grains and precipitating the strengthening phase Al3Mg2 weakens. The trend of work hardening affecting strength is that it first increases, reaches a peak, and then decreases. Based on the elongation of 5A06 aluminum alloy being approximately 22%, it can be determined that among the three deformation amounts, the sample with a deformation of 16% has the lowest residual stress; the sample with a deformation of 24% has strength near the peak value and the highest residual stress; the sample with a deformation of 32% has strength exceeding the peak value, and the residual stress is between samples d and e. Therefore, the distribution of the granular Al3Mg2 phase is as follows: d, f, e have the highest, followed by the lowest, and then the least. (See...) Figure 1 (d) Figure 1 (f) and Figure 1 (e). Therefore, it can be determined that the hardness of the samples also decreases sequentially in this order. This is consistent with the hardness test results, as shown in Table 2. The deformation treatment of metallographic samples g, i, and h is the same as that of metallographic test samples d, f, and e, except that the cryogenic treatment time is changed to 72 hours. From Figure 1 of (g), Figure 1 of (i), Figure 1 As can be seen from (h), the distribution pattern of granular Al3Mg2 phase in the sample structure is similar to that of metallographic samples d, f, and e, and is consistent with the hardness test results.

[0044] Compare separately Figure 1 (d) and Figure 1 of (g), Figure 1 (e) and Figure 1 of (h) Figure 1 (f) and Figure 1 As can be seen from (i), while maintaining the same amount of deformation, the amount of Al3Mg2 phase in the sample microstructure increases with the extension of cryogenic treatment time. The degree of increase is significant. Figure 1 (g) is more significant. Figure 1(i) next, and lastly Figure 1 The corresponding hardness test results also show the same variation pattern.

[0045] Comprehensive analysis shows that cryogenic treatment has a relatively small effect on the hardness of 5A06 aluminum alloy when there is no deformation, but the hardness increases with time. Under different deformation states, the hardness of the samples increases with the extension of cryogenic treatment time. The effect of cryogenic treatment varies depending on the deformation conditions. Keeping the treatment time constant, the alloy hardness first decreases and then increases with the increase of alloy deformation, showing a minimum hardness value, which is related to the limit stress of work hardening in the alloy. It can be seen that cryogenic treatment time and deformation amount are key factors affecting the microstructure and properties of the alloy.

[0046] The preferred process conditions for improving the hardness of 5A06 aluminum alloy according to this invention are: 16% deformation + cryogenic treatment for 72 hours. Under these preferred process conditions, the hardness of 5A06 aluminum alloy is 103.5 HB.

[0047] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A process for improving the hardness of 5A06 aluminum-magnesium alloy, characterized in that: Includes the following steps: Step 1: Machining the 5A06 aluminum alloy bar to produce several cylindrical short samples; Step 2: Deform the sample: Compress the sample once, with a deformation amount of 16%; Step 3: Immerse the deformed sample directly in liquid nitrogen for cryogenic treatment, then place it in air to warm to room temperature, and measure the hardness of the sample. The cryogenic treatment time is 72 hours; the cylindrical short sample has a diameter of 15 mm and a height of 25 mm.

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