A new die-cast magnesium alloy for applications at higher elevated temperatures of 200-300°C

摘要

The development of lightweight magnesium(Mg)alloys capable of operating at elevated temperatures of 200-300°Cand the ability of using high pressure die casting for high-volume manufacturing are the most advanced developments in manufacturing critical parts for internal combustion engines used in power tools.Here we report the microstructure and mechanical properties of a newly developed die-cast Mg-RE(La,Ce,Nd,Gd)-Al alloy capable of working at higher elevated temperatures of 200-300°C.The new alloy delivers the yield strength of 94 MPa at 300°C,which demonstrates a 42%increase over the benchmark AE44 high temperature die-cast Mg alloy.The new alloy also has good stiffness at elevated temperatures with its modulus only decreasing linearly by 13%from room temperature up to 300°C.Thermal analysis shows a minor peak at 364.7°Cin the specific heat curve of the new alloy,indicating a good phase stability of the alloy up to 300°C.Nd and Gd have more affinity to Al for the formation of the minority of divorced Al-RE(Nd,Gd)based compounds,and the stable Al-poor Mg_(12)RE(La_(0.22)Ce_(0.13)Nd_(0.31)Gd_(0.31))Zn_(0.39)Al_(0.13)compound acts as the continuous inter-dendritic network,which contribute to the high mechanical performance and stability of the new die-cast Mg alloy at 200-300°C.