Direct observation of martensitic reversion from lenticular martensite to austenite in Fe-Ni alloy

Martensitic reversion from lenticular martensite to austenite was investigated in Fe-29%Ni alloy. Martensitically reversed austenite has essentially the same crystal orientation as untransformed austenite, which means that the crystallographic reversibility appears even in non-thermoelastic martensitic transformations. On the other hand, a small amount of the reversed austenite forms having a specific twin orientation with respect to the untransformed austenite. The formation of twined austenite reveals that reversed austenite nucleates at the untransformed austenite/martensite interface and grows into the interior of lenticular martensite. In addition, it was found that martensitically reversed austenite contains high-density dislocations leading to a significant strengthening.