冷却工艺对7A04铝合金组织与性能的影响

Effect of Cooling Process on Microstructure and Properties of 7A04 Al-alloy

研究了不同冷却介质对高温固溶7A04铝合金组织及性能的影响规律。结果表明:冷却介质对固溶态7A04铝合金的微观组织、强度及断口形貌有较大的影响。高温固溶后采用空冷处理,基体中的第二相数量较少,屈服强度及拉伸强度较低,韧性较差,断口中出现大量平整断裂面;而高温固溶后采用油冷处理,基体中出现一定数量的第二相组织,拉伸强度及屈服强度有所提高,韧性有所改善;高温固溶后采用水冷处理,基体中的第二相组织数量增多,力学性能进一步提高,断口中出现少量较小较深的断裂韧窝。高温固溶后采用液氮深冷处理,基体中出现大量的第二相组织,且弥散分布在晶内及晶界,屈服强度及拉伸强度最高,分别为570 MPa和700 MPa,断口中出现大量的较深、较小韧窝。因此,7A04铝合金的最佳冷却工艺为高温固溶后采用深冷处理。

The effect of different cooling medium on the microstructure and mechanical properties of 7A04 aluminum alloy after high temperature solid solution was investigated. The results show that cooling medium in high-temperature treatment has a significant influence on the microstructure, strength and fi＇acture morphology. Via air cooling after high temperature solid solution, the number of second phase in matrix is relatively less, and the yield strength, tensile strength and the toughness are poorer, with a large amount of flat fracture surface. Using oil cooling, a certain amount of second phase appears in the matrix, and the tensile strength, yield strength and toughness improve. Adopting water cooling, the second phase significantly increases, and the mechanical properties further improves, with a small amount of deep and small dimples. Using liquid nitrogen cooling, a large amount of second phase appear in the grain and grain boundary, and the yield strength and tensile strength is 570 MPa and 700 MPa, respectively, and a large amount of deep and small dimples occur in the fi＇acture surface. Hence, 7A04 aluminum alloy via liquid nitrogen cooling treatment after high temperature solid solution has the optimum mechanical properties.