Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5455869 | Materials Science and Engineering: A | 2017 | 32 Pages |
Abstract
Effects of minor Sr (x=0, 0.2, 0.6, 1.0 wt%) addition on microstructure, mechanical properties and creep behavior of high pressure die casting AZ91-0.5RE based alloys were thoroughly investigated. Experimental results show that the addition of Sr to HPDC AZ91-0.5RE based alloys can refine the microstructure including externally solidified crystal α-Mg and eutectic compound β-Mg17Al12. On the other hand, when the content of Sr reaches 1.0%, a small amount of plate-like Al4Sr phase can be formed. Moreover, minor of Sr addition can significantly decrease the volume fraction of β-Mg17Al12 precipitates of AZ91-0.5RE based alloys. In addition, the mechanical properties of AZ91-0.5RE based alloys can be improved remarkably with Sr addition, and the alloy containing 0.2% Sr exhibits the best mechanical properties at ambient temperature. Fractographic analyses demonstrate that the fracture modes of the alloy without and with Sr are quasi-cleavage fracture and ductile fracture, respectively. Furthermore, Creep properties of HPDC AZ91-0.5RE based alloys were obviously improved by adding Sr element. And creep mechanisms of the alloys with and without Sr at 150 °C/30-70 MPa and 50 MPa/140-160 °C are both considered to be dislocation climb controlled creep based on the analyses of the stress exponent and apparent activation energy. The AZ91-0.5RE-1.0Sr alloy presents the best creep resistance among the studied alloys, which is mainly attributed to the presence of thermally stable intermetallic compound of Al4Sr phase at the grain boundaries.
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Authors
Dongdong Zhang, Deping Zhang, Fanqiang Bu, Xinlin Li, Kai Guan, Qiang Yang, Shaohua Liu, Xiaojuan Liu, Jian Meng,