Uncovering the effect of basal texture tilting angle on the room-temperature stretch formability of magnesium alloy sheets and its underlying mechanisms

Tilting basal texture is recognized as a potentially effective strategy for optimizing the room–temperature (RT) formability of magnesium alloy sheets. However, the unclear quantitative relationship between the RT formability and basal texture tilting degree of magnesium alloy sheet as well as the unrevealed intrinsic mechanisms linking them renders this strategy immature yet. This work comprehensively investigates the influence of basal texture tilting angle (BTTA) on the RT stretch formability of AZ31 magnesium alloy sheets, as well as the plastic deformation mechanism operation and strain accommodation capability during forming process. The results show that the formability of every texture-effectively tilted sheet with a BTTA > 0° is significantly improved as compared to that of initial sheet orientating the c-axis of most grains toward the normal direction. Moreover, the formability optimization effect exhibits a trend of initial increase followed by decrease with increasing BTTA, which is primarily attributed to the differential response behaviors of plastic deformation mechanism operation and strain accommodation to BTTA in the upper regions among these sheets. Given that BTTA is > 0° but < 60°, basal slip dominates the plastic deformation. The positive correlation between formability gain and BTTA benefits greatly from the continuously enhanced initial basal slip ability and the reduced orientation hardening rate. When BTTA is ≥ 60° but < 90°, the strong synergistic effect combining {10 1 ¯ 2} tensile twinning with basal slip, along with the orientation softening for basal slip, promotes the formability improvement. Once BTTA approaches 90°, the profuse formation of {10 1 ¯ 2} tension twin is a main contribution to the formability increment. Additionally, the evolution pattern of thickness-direction strain accommodation capability ( r avg. value) with increasing BTTA is completely consistent with the I.E. value. Specially, due to the strong initial basal slip ability, numerous tension twins with soft orientation for basal slip formed during the early forming stage, the continuous orientation softening for basal slip in matrix and the highest thickness-direction strain accommodation capability, the sheet with a BTTA of 60° shows the optimal RT formability manifested as an I.E. value of 7.6 mm which represents a ∼217% enhancement compared to the initial sheet with a BTTA of 0°. This work deepens the understanding of tilting basal texture for optimizing formability and provides theoretical foundations for the reverse design and development of magnesium alloy sheets with high RT formability.