Cu对Al-Zn-Mg-Xcu合金组织、断裂及淬透性的影响

Effect of Cu on Microstructure,Fracture and Hardenbility of Al-Zn-Mg-XCu Alloy

采用光学显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)以及室温拉伸、末端淬火等测试方法,研究了Cu对Al-7.6Zn-1.6Mg-XCu合金组织、断裂和淬透性的影响.研究表明:随着Cu质量分数的增加,合金的强度先增加后减小,合金的强度在Cu质量分数为1.70%时出现峰值;合金的力学性能各向异性随Cu质量分数的增加,先减小再增大,Cu质量分数为1.45%时,合金的力学性能各向异性最小;随着Cu质量分数的升高,合金横向断裂模式从以穿晶断裂为主向沿晶断裂转变.与合金纵向延伸率变化幅度比较,Cu质量分数对合金横向延伸率影响更加显著.随着Cu质量分数的升高和淬火速率降低,合金时效后平衡相的周围出现明显的无沉淀析出带,导致合金硬度下降明显,淬透性也大大降低.

The effect of Cu content on the microstructure,fracture and hardenbility of Al-7.6Zn-1.6Mg-XCu alloy was investigated by means of mechanical tensile and jominy end quench testing combined with optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results showed that the strength of the alloys increased first and then decreased with the increase of Cu mass fraction,and the strength of the alloy peaked at Cu mass fraction of1.70%.The anisotropic mechanical properties of the alloys decreased first and then increased with the increase of Cu mass fraction,and the alloys had the minimum anisotropy when the Cu mass fraction was1.45%.Concomitant with the increase of Cu mass fraction,a transition in fracture mode was observed from predominantly transgranular dimpled rupture to predominantly intergranular dimpled rupture.Compared with the change of the longitudinal elongation of the alloys,the Cu mass fraction had a significant effect on the transverse elongation of the alloys.With the increase of Cu mass fraction and the decrease of quenching rate,obvious precipitation free zone(PFZ)was observed around the equilibrium phases of the alloys after aging,which resulted in significant reduction in hardenability and hardness of the alloys.