Aging behavior and fatigue crack propagation of high Zn-containing Al-Zn-Mg-Cu alloys with zinc variation

作     者：Kai Wen Yunqiang Fan Guojun Wang Longbing Jin Xiwu Li Zhihui Li Yongan Zhang Baiqing Xiong 

作者机构：State Key Laboratory of Non-ferrous Metals and ProcessesGeneral Research Institute for Nonferrous Metals Northeast Light Alloy Co.Ltd. 

出 版 物：《Progress in Natural Science:Materials International》 (自然科学进展·国际材料(英文))

年 卷 期：2017年第27卷第2期

页      面：217-227页

核心收录：

学科分类：08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学] 0702[理学-物理学] 

基　　金：financially supported by the National Key Research and Development Program of China (No.2016YFB0300803,No.2016YFB0300903) the National Program on Key Basic Research Project of China (Nos.2012CB619504) the National Natural Science Foundation of China (No.51274046) 

主　　题：Al-Zn-Mg-Cu alloy Fatigue crack propagation Precipitate Aging treatment 

摘      要：In the present work, the influence of two-step aging treatments on hardness, electrical conductivity and mechanical properties of two high Zn-containing Al-Zn-Mg-Cu alloys with zinc content variation was investigated and the detailed T76 aging parameters were proposed. The microstructure of the precipitates were studied by transmission electron microscopy(TEM) and high-resolution transmission electron microscopy(HREM) and then quantitatively investigated with the aid of an image analysis. The fatigue performances were researched by the fatigue crack propagation(FCP) rate test and fracture morphology was observed with scanning electron microscopy(SEM). The results show that the matrix precipitate size distributions of both alloys had significant difference, so as to fatigue crack propagation rates and fracture appearance. The shear and bypass mechanisms of dislocation-precipitate interactions were employed to explain the difference. Among the shearable precipitates, the proportion of larger size precipitates for the higher zinc content alloy is bigger than that for the lower zinc content alloy. The coarse shearable precipitates hinder the propagation of the fatigue cracks, leading to inferior FCP rate. For both alloys, the shear mechanism possesses the dominant factor, finally causing a preponderance in the FCP resistance for the higher zinc content alloy than the lower one.