Simultaneously improving elastic modulus and damping capacity of extruded Mg-Gd-Y-Zn-Mn alloy via alloying with Si

Abstract

Developing magnesium (Mg) alloys with both high elastic modulus and damping capacity is a long-term challenge in the field of lightweight metals. Herein, it is shown that alloying with Si in Mg-Gd-Y-Zn-Mn simultaneously increased the elastic modulus and damping capacity. After Si alloying, the LPSO phase was greatly reduced and a large number of (RE + Si)-rich particles were formed. Due to the contribution of the high modulus second phases, the elastic modulus of the extruded Mg-Gd-Y-Zn-Mn alloy with a trace amount of Si was 49.3 GPa, 8 GPa greater than that of the extruded pure Mg. In addition, the extruded Mg-Gd-Y-Zn-Mn-Si alloy possessed good damping capacity at both room temperature (RT) and high temperature. At high strain amplitude, the extruded Mg-Gd-Y-Zn-Mn-Si alloy achieved a RT damping value of Q−1 > 0.01, significantly higher than the extruded pure Mg, which was related to the high density of thermal mismatch dislocations in the vicinity of the interfaces between the reinforcing phase and the α-Mg matrix. With the increasing temperature, the extruded Mg-Gd-Y-Zn-Mn-Si alloy showed obviously higher damping capacity than the extruded Si-free alloy, which was attributed to the incoherent phase interfaces, weakened texture and thermal mismatch dislocations.