Analysis of microstress distribution non-uniformity in the rolling deformation process of ultra-thin magnesium alloy sheets

This paper analyzes the micro-scale stress distribution non-uniformity during the single-pass rolling process of ultra-thin magnesium alloy sheets. By establishing a macro-micro scale simulation of the rolling process and combining it with experimental investigations, the study explores the effects of different strain rate ratios on stress distribution in the Normal Direction (ND, refers to the thickness direction of the sheet) and Rolling Direction (RD, aligns with the axis of rolling deformation), as well as on the slip systems. This study investigates the microstress distribution non-uniformity in 0.5 mm ultra-thin AZ31 magnesium alloy sheets during single-pass rolling. Experimental and simulation results reveal that increasing the strain rate ratio from 1:1 to 1:2 reduces the rolling force by 8 kN (125 kN–117 kN) and decreases the principal stress in the ND from −125 MPa to −80∼-60 MPa, with stress non-uniformity concentrated at grain boundaries. In the RD, a tensile-compressive mixed state induces stress peaks exceeding 56 MPa. The activation of basal and prismatic slip systems generates opposing shear stresses (−45 MPa vs. +24 MPa), exacerbating intergranular stress conflicts. The direction and distribution of shear stress in different slip systems vary due to differences in grain orientation and the slip stages, resulting in stress conflicts between grains and the formation of opposing positive and negative stress phenomena. These findings demonstrate that adjusting strain rate ratios and texture control can effectively alleviate stress concentration and improve formability, providing critical insights for optimizing industrial rolling processes of ultra-thin magnesium alloy sheets.