高纯Al-Cu-Mg-Ag合金的多级断续时效工艺研究

采用拉伸力学性能测试、透射电镜微观组织分析、扫描电镜断口分析等方法,研究高纯Al-Cu-Mg-Ag合金多级断续时效工艺对合金力学性能及微观组织的影响。结果表明,二级时效温度为室温和65℃时,合金强化效果主要来源于固溶强化和GP区,时效时间对合金强度影响很小。二次时效温度高于100℃时,合金的主要强化相由θ′相逐渐转变为Ω相。适当延长时效时间可使合金获得最大的强化效果。与T6I4和T6I6热处理工艺相比,采用185℃,20min预时效后水淬+150℃/25～50h的多级断续时效工艺极大缩短热处理周期并简化工序,同时合金的强度水平与T6态相当,而塑性获得显著改善。

多级时效对汽车用Al-Mg-Zn-Cu-Sn合金微观组织和性能的影响

采用拉伸试验、TEM、SEM等测试手段,研究了不同多级时效热处理下汽车轻量化用Al-Mg-Zn-Cu-Sn铝合金的力学和组织性能。研究结果表明:合金基体中存在白色的粗大第二相组织,主要存在AlZnMgCu相与Al7Cu2Fe杂质相。二级时效处理后在晶粒中形成了许多细小析出相,合金晶界析出η相。对合金进行时效处理时生成强化相沉淀的顺序是先转变为α过饱和固溶体,再进入GP区,之后形成η’相,最终转变为η相。对合金进行二级时效处理后,产生众多GP区与η’相,起到明显的强化效果。采用二级时效方法进行处理后,合金拉伸强度与屈服强度达到641. 05 MPa与596. 42 MPa,伸长率12. 16%。在合金的断口区域形成了沿晶断裂与穿晶韧窝断裂,经过二级时效处理后形成许多韧窝状的穿晶断口;经过三级时效处理后有些韧窝深度与外径都较大。

Multistage-aging process effect on formation of GP zones and mechanical properties in Al-Zn-Mg-Cu alloy

The tensile properties and fatigue behavior of an Al-Zn-Mg-Cu alloy were investigated by performing tensile tests and fatigue crack propagation （FCP） tests. The tensile results show that lower aging temperature modified retrogression and re-aging （RRA） process enhances the elongation, but reduces the strength of the alloy, as compared to conventional RRA process which employs peak aging temperature. Both ductility and strength, however, are increased by employing a natural aging prior to re-aging based on the former modified RRA process. Fatigue test results show that both routes reduce FCP rate. Especially, the lower re-aging temperature modified RRA process obtains the lowest FCP rate. Natural aging treatment could enhance the nucleation rate of GP zones. A large amount of GP zones could be cut by dislocations, which is responsible for the highest tensile strength and elongation, as well as lower FCP rate.