Achieving enhanced mechanical properties in the Mg-Y-Zn-V alloy by refining grains and improving the morphology and distribution of LPSO via pre-forging and subsequent rolling

In this work, Mg-7Y-5Zn-0.1V alloys were prepared by 1-D forging followed by multi-step rolling. The rolling reduction dependence of the microstructure and tensile properties of the Mg-7Y-5Zn-0.1V alloy was experimentally investigated. The results indicated that the bimodal matrix microstructures are formed, and the fibrous 18R long-period stacking ordered (LPSO) phase and kinked 14H-LPSO phase are observed after 1-D forging. As the rolling deformation increased, the fibrous 18R-LPSO fractured into block and distributed more homogeneous. The lamellar 14H-LPSO fractured more severely, and it re-precipitated within the matrix when the deformation reached 50 %. The average grain size decreased gradually with increasing rolling deformation, and the minimum was 5.07 mu m. After rolling, the {0001} <11 2 0> and {0001} <101 0> textures disappeared. The grain refinement of rolling alloy was mainly due to the fact that dynamic recrystallization (DRX) and substructures were generated within some grains, while the forging alloy was mainly due to DRX. The mechanisms of DRX were discontinuous DRX (DDRX) and twin-induced DRX (TDRX) after forging, and continuous DRX (CDRX) and DDRX after rolling. The strength reached its maximum when the rolling deformation amount reached 60 %, with a yield strength (YS) of 350 MPa and an ultimate tensile strength (UTS) of 385 MPa. Compared to the as-cast Mg-7Y-5Zn-0.1V alloy, its strength increased by 56 % and 63 %, respectively. The improvement of mechanical properties was mainly attributed to fine grain strengthening and dislocation strengthening.