A systematic study on hot-rolled high-strength WE43 Mg-RE alloy: formability, microstructures, mechanical properties, and strengthening mechanism

As one of the most successful commercial light-weight Mg alloys, WE43 (Mg–4Y-3Nd-0.5Zr, wt.%) alloy shows wide application potentials in the automobile and aerospace fields. However, at present, the value of expensive rare earth (RE) elements in WE43 alloy has not yet been maximumly exerted, since that this alloy is still mostly prepared with conventional casting method which limits its strength level. In this paper, hot-rolling plastic deformation is employed to prepare high-strength WE43 alloy. The effects of rolling parameters (temperature 480 °C-520 °C, reduction 20–90 %) on the formability, and effects of subsequent T5 treatment (225 °C × 0–64 h) on the microstructures and mechanical properties have been systematically investigated. The results show that, temperature 500 °C and reduction ≤80 % can be selected as the preparation parameters that can ensure excellent formability for WE43 alloy. After hot-rolled at 500 °C with 50 % reduction plus 225 °C × 4 h T5 treatment, WE43 alloy exhibits the optimal mechanical property, i.e., YS 316.0 ± 1.7 MPa, UTS 352.2 ± 4.8 MPa, and EL. 3.4 ± 0.1 %, which is remarkably improved by 82 %, 57 %, and 113 %, respectively, when compared with cast-T6 counterpart. Based on the EBSD and TEM results, the strengthening mechanisms have been semi-quantitatively analyzed, showing that the main contributions can be attributed to grain refinement strengthening, precipitation strengthening, and texture strengthening. This paper provides a comprehensive understanding of the low-cost and convenient hot-rolling preparation process of high strength WE43 alloy, and will greatly benefit to expanding engineering applications of Mg-RE alloys.