Influence of minor RE addition on microstructures, tensile properties, and creep resistance in a die-cast Mg–Al–Ca–Mn alloy
Deping Zhang, Boqiong Li, Jinhui Zhang, Ting Niu, Chunlin Li, Peng Cheng, Liuqing Yang
Abstract
In this work, we have investigated the influence of RE content on the tensile property, creep resistance, and microstructures of a die-cast Mg-9Al-0.3Ca-0.2Mn (wt. %). Minor content of RE elements simultaneously increases the strength and ductility, which is mostly since RE addition refined primary dendritic α-Mg and eutectic α-Mg matrix and eutectic β-Mg17Al12 phases and formed thermally stable Al11RE3 phases. The 0.6% RE adding alloy obtains the best strength-ductility synergy along with the UTS of 245 MPa, TYS of 170 MPa, and EL of 5.7%. The 0.6−1.0% RE addition gives rise to a reduction of the minimum creep rate by over one order of magnitude of the alloy, indicating a significant enhancement in creep resistance, which can be mainly attributed to RE addition introducing Al11RE3 phases to prevent grain boundary sliding, and suppressing dynamic precipitation of γ-Mg17Al12 phases during high-temperature creep. These results can provide important references for the design of creep-resistant die-cast Mg alloys and promote the application of commercial Mg-Al based alloys at high temperatures.