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Significantly enhanced the ductility of the fine-grained Al–Zn–Mg–Cu alloy by strain-induced precipitation

2015; Elsevier BV; Volume: 88; Linguagem: Inglês

10.1016/j.matdes.2015.09.023

1873-4197

Yujing Lang, Guxin Zhou, Longgang Hou, Jishan Zhang, Linzhong Zhuang,

Aluminum Alloys Composites Properties

A fine-grained structure of Al–Zn–Mg–Cu alloy was produced by a successive two-step deformation (STD) process based on strain-induced precipitation (SIP). The fine-grained alloy treated by the STD process exhibited significantly superior tensile ductility than the conventional hot-deformed (CHD) alloy. Effects of the STD process on microstructure and mechanical properties were investigated, in conjunction with fracture characterizations. Numerous spherical precipitates and dense dislocations were induced by the SIP at 300 °C. A fine lamellar structure was formed during subsequent heating and hot deformation of the STD process, finally contributing to the fine-grained T6-aged alloy. Due to the fine-grained structure, more dimples in the fracture surface of the STD treated alloy were produced than those of the CHD treated alloy. TEM in-situ testified that the grain boundary precipitates (GBPs) originated the initiation of micro-cracks, and the cracks propagated along the (sub)grain boundaries during the tensile loading. The initiation and propagation of micro-cracks were explained in terms of grain boundary precipitates (GBPs), precipitation free zones, and grain refinement. Although initiation and propagation of the cracks easily occur to coarse GBPs and grain boundaries, the fine-grained structure obtained by the STD treatment could effectively delay these behaviors and improve mechanical properties.