RRA处理对7085铝合金微观组织演变及性能的影响

Influence of RRA treatment on microstructure evolution and properties of 7085 aluminum alloy

通过对微观组织的TEM精细表征、断口的SEM观察、力学性能和导电率的测试等,研究了回归再时效处理(RRA)对7085铝合金微观组织演变及性能的影响。结果表明:回归温度越高,RRA处理后达到峰值硬度的时间越短,导电率增加速率越快;120℃×24 h预时效+200℃×8 min回归处理+120℃×24 h再时效为最佳的RRA工艺,抗拉强度、屈服强度和伸长率分别达到735 MPa、698 MPa和8. 5%,导电率达到44. 5%IACS;回归处理后的谷值硬度,与RRA处理后试样的峰值硬度达到时间一致;RRA处理后晶内主要为与基体呈共格关系的GP区和η’粒子,晶界附近存在宽度在70~80 nm的PFZ区。

Influence of retrogression and reaging(RRA)treatment on microstructure evolution and properties of 7085 aluminum was investigated.The microstructure was characterized by using TEM,the fracture was observed by using SEM,and the conductivity and properties was tested.The results indicate that the higher the retrogression temperature,the faster the arriving of peak value of hardness and conductivity.The best RRA process is 120℃×24 h pre-aging+200℃×8 min retrogression+120℃×24 h reaging,when treated with best RRA process,the tensile strength,yield strength and elongation of the tested alloy reach 735 MPa,698 MPa and 8.5%,respectively,while the conductivity arrives 44.5%IACS.The reaching time of hardness peak value after RRA is coincided with that of valley value after retrogression.The crystal mainly consists of GP zones andη’phase which are coherent with matrix,and there is a PFZ zone with a width of70-80 nm near grain boundary.