Microstructural Evolution, Mechanical Property, and Strengthening in a Lightweight Mg-Y-Zn-Mn Alloy Fabricated by Multidirectional Forging and Hot Rolling

To explore the room-temperature strength and strengthening mechanism, a new Mg-6.35Y-3.47Zn-1.42Mn (wt.%) alloy has been fabricated by novel multidirectional forging and hot rolling. The microstructures, mechanical properties, and strengthening mechanism were studied. The average grain sizes after three-pass multidirectional forging and hot rolling were 7.46 ± 1.5 μm and 6.82 ± 1.5 μm, respectively. Microstructural characterization showed that the present alloy consists of α-Mg solid solution matrix phase and long period stacking ordered (LPSO) structure phase. A Vickers hardness of 108.58 was obtained following multidirectional forging and hot rolling. An ultimate tensile strength of 315.36 ± 4 MPa, yield strength of 196.09 ± 5 MPa, and elongation of 8.87% were achieved in this alloy. The strengthening contribution of this alloy was obtained through strengthening model estimation. The contribution of LPSO structure strengthening, dislocation strengthening, and grain boundary strengthening to the yield strength accounted for 81.72% of the yield strength. This estimation provides a guidance to the alloy and processing design strategy for commercial application in future. Finally, the relationship between this alloy processing and advanced manufacturing was discussed.