Martensite deformation during the phase transformation of TiNi shape-memory alloy under constraint

Martensite deformation in constrained phase transformation of TiNi shape memory alloy has been studied with differential scanning calorimeter (DSC) and strain recovery measurements. It is shown that martensite deformation occurs in both the reverse and forward transformations for prestrained TiNi shape memory alloy fibers under constraint with constant strain. Two sorts of martensite, the redeformed martensite and the inheriting deformation martensite, exist after a constrained thermal cycle. In the subsequent free reverse transformation, two-stages of strain recovery appear corresponding to the reverse transformations of the inheriting deformation martensite and the redeformed martensite, respectively.