The interaction evolution between thermally activated precipitates and deformation-induced ' martensite in a metastable -Zr alloy

In this study, the interaction evolution between the alpha precipitates that are thermally actived and deformationinduced alpha ' martensite in a metastable beta-Zr alloy during tensile deformation was investigated. Following a twostep heat treatment, it results in the simultaneous precipitation of the thermally activated alpha phase in both within the beta grain (alpha(IN)) and at the grain boundaries (alpha(GB)). The microstructure after deformation demonstrates that the alpha ' martensite induced by deformation initially nucleates and subsequently develops into elongated plates that are parallel with each other in the spaces between the alpha(IN). As deformation continues, the alpha ' martensite grows rapidly in the length direction, firstly facing initial obstruction from alpha(IN), but finally penetrating it and persisting to develop further. However, the growing alpha ' martensite encounters alpha(GB), it is prevented completely from growing in length direction and instead grows quickly in width direction. Furthermore, alpha ' martensite plates further thicken and merge with each other, ultimately enveloping the complete beta grain, including alpha(IN), to construct an alpha ' martensite domain featuring an unusual shell-core arrangement. The shell layer is alpha(GB )and the core layer is alpha ' martensite surrounding alpha(IN). Meanwhile, the secondary deformation product, namely {1011} twins, will form within alpha ' martensite domain in subsequent deformation process.