<i>In-situ</i> observations of a hierarchical twinning–detwinning process in stress-induced <i>α</i><sup>″</sup>-martensite of Ti-12Mo alloy
Bingnan Qian, Min Yang, Lola Lilensten, P. Vermaut, Fan Sun, F. Prima
Abstract
Beyond classic martensitic transformation-induced plasticity (TRIP), consecutive hierarchical twinning in the primary martensite is observed providing additional tensile strain about two-to-three times higher than the original transformation strain. The hierarchical twinning, operating in two different modes, contributes to at least one quarter of the plasticity in TRIP/TWIP Ti-12Mo alloy at early deformation stage. During tensile unloading, a peculiar multi-step detwinning process reverses the mechanically twinned martensite to its original orientation, resulting in rubber-like behavior. The complex reversible twinning process is investigated by combining in-situ EBSD/TEM experiments and theoretical rationalization with respect to Schmid factors and twin variant selection.