Effect of Pre-aging - Warm Forming Process Parameters on Microstructure and Properties of 7075 Aluminum Alloy
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摘要:
对7075-T6铝合金进行了不同预时效温度（85,100,120 ℃）、预时效时间（0~32 h）、成形温度（150,200,250,300 ℃）的预时效-温成形处理,研究了工艺参数对合金组织和性能的影响,确定了最佳工艺参数。结果表明：随着预时效时间延长,7075铝合金晶粒尺寸无明显变化,析出相数量增加,硬度和强度均先增大后减小；相比预时效温度为100,120 ℃时,预时效温度为85 ℃时析出相的数量较少,尺寸较小,硬度和强度较大,断后伸长率较小；随着温成形温度升高,硬度和强度均减小；最佳预时效-温成形工艺参数为预时效温度85 ℃、预时效时间24 h、温成形温度150 ℃,此时合金综合性能最佳,抗拉强度和断后伸长率分别为T6态的95%和163%；成形后经180 ℃×30 min烘烤处理可提升其强度、降低塑性。
Abstract:The 7075 aluminum alloy was pre-aged and warm formed at different pre-aging temperatures (85, 100, 120 ℃) for different pre-aging times (0–32 h) and forming temperatures (150, 200, 250, 300 ℃). The effect of process parameters on the microstructure and properties of alloy was studied. The optimum process parameters were determined. The results show that with the extension of pre-aging time, the grain size of 7075 aluminum alloy had no obvious change, the amount of precipitated phase increased, and the hardness and strength increased first and then decreased. Compared with those at pre-aging temperature of 100, 120 ℃, the number and the size of precipitated phases were smaller, the hardness and strength were larger, and the percentage elongation after fracture was smaller at the pre-aging temperature of 85 ℃. The hardness and strength decreased with the increase of warm forming temperature. The optimum pre-aging-warm forming process parameters were listed as follows: pre-aging temperature of 85 ℃, pre-aging time of 24 h, and warm forming temperature of 150 ℃. At this time, the alloy had the best comprehensive properties, which had the tensile strength and percentage elongation after fracture were 95% and 163% of those of the 7075-T6 aluminum alloy, respectively. Baking at 180 ℃ for 30 min after forming could improve the strength and reduce the ductility.
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Keywords:
- 7075 aluminum alloy /
- pre-aging /
- warm forming /
- baking
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图 2 85 ℃下预时效不同时间并在150 ℃下温成形后7075铝合金的显微组织与晶粒尺寸
Figure 2. Microstructures and grain size of 7075 aluminum alloy after pre-aging at 85 ℃ for different times and warm forming at 150 ℃
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图 3 不同温度下预时效24 h并在150 ℃下温成形后7075铝合金的显微组织
Figure 3. Microstructures of 7075 aluminum alloy after pre-aging at different temperatures for 24 h and warm forming at 150 ℃
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图 4 不同温度预时效不同时间并在150 ℃下温成形后7075铝合金的力学性能
Figure 4. Mechanical properties of 7075 aluminum alloy after pre-aging at different temperatures for different times and warm forming at 150 ℃: (a) hardness; (b) tensile strength; (c) yield strength and (d) percentage elongation after fracture
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图 5 不同温度下预时效不同时间并在150 ℃下温成形后7075铝合金的拉伸断口形貌
Figure 5. Tensile fracture morphology of 7075 aluminum alloy after pre-aging at different temperatures for different times and warm forming at 150 ℃
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