Effects of heat treatment on mechanical properties of an extruded Mg-4.3Gd-3.2Y-1.2Zn-0.5Zr alloy and establishment of its Hall-Petch relation

The effects of T4, T5, and T6 treatment on the microstructure and mechanical properties of the extruded Mg-4.3Gd-3.2Y-1.2Zn-0.5Zr (wt.%) alloy with a relatively low RE content (7.5 wt.%) were investigated. T4 treatment at 450-500 degrees C induces a gradual grain growth of alpha-Mg but an obvious transition of texture component from < 0001 >perpendicular to ED to < 0001 >parallel to ED. Interdendritic LPSO phases are highly stable against annealing while intragranular ones experience dissolution and re-precipitation. After peak-ageing at 200 degrees C, the elongation of as-extruded and T4 samples is just slightly reduced or even increased due to the weak ageing hardening response. T5 sample exhibits an attractive combination of strength and ductility, with a tensile yield strength (TYS) of 303 MPa and elongation of 20.0%. The Hall-Petch relation for the alloys with or without ageing treatment has been estimated. Grain boundary strengthening rather than precipitation strengthening has the dominant contribution to TYS, and a modified equation is developed to predict grain boundary strengthening values for Mg-Gd-Y-Zn-Zr alloys which contain different Schmid factors for basal slip. (c) 2020 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.

Automated summary

The effects of different treatments on the microstructure and mechanical properties of an extruded Mg-4.3Gd-3.2Y-1.2Zn-0.5Zr alloy were investigated. The study found that grain growth, texture changes, and stability of LPSO phases have an impact on the alloy's properties.