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

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 alpha-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. (C) 2019 Elsevier B.V. All rights reserved.