Synergistic strengthening mechanism of gradient structure AZ31 magnesium alloy plate in hard plate rolling

Compared with homogeneous structural materials, gradient structural materials are easier to realize the strength-ductility optimization. Research on the strengthening mechanism of different gradient structure materials is a meaningful way to broaden the application of gradient structure materials. In this paper, the AZ31 magnesium alloy plate was rolled by hard plate rolling. The gradient structure was controlled by changing the initial plate thickness. When the initial plate thickness was 4 ​mm, AZ31 magnesium alloy shows excellent strength and ductility, the tensile strength was 282.2 ​MPa, and the ductility was 28.4 ​%. The change of the initial plate thickness changes the stress state which forming a gradient structure with different characteristic layers. The extra strengthening between different characteristic layers improves the properties of gradient structure, which makes the magnesium alloy change from a uniaxial stress state to a multi-axial stress state during the tensile process. The increase of the characteristic layer induces more geometrically necessary dislocation accumulation, improving the gradient structure's strength and ductility. This research provides a new design strategy for the forming and performance optimization of gradient structure magnesium alloy plate by hard plate rolling, which has good industrial production and application potential.