Phase Transformation in Fe Alloys Induced by Surface Treatment

Difference of the phase transformation behavior at deformation-induced layer depending on surface treatment methods was investigated using Fe-33mass%Ni alloy. As specimens, two kinds of specimens were prepared. One specimen has austenite (γ) single structure, and the other specimen consists of both martensite (α’) and γ phases. Using these specimens, shot-peening tests were performed, and then phase transformation behavior induced by the shot-peening was compared with that by sliding wear reported in previous literature. The deformation-induced layer induced by shot-peening has very fine microstructure consisted of both α’ and γ phases. The microstructure in the deformation-induced layer formed by shot-peening becomes similar with increasing duration of shot-peening regardless of initial microstucture. On the other hand, the deformation-induced layer induced by sliding wear is reported to have γ single structure regardless of initial microstructure. This microstructural difference between shot-peening and sliding wear comes from the difference of heat generation during the surface treatment. Therefore, it is concluded that phase transformation behavior in deformation-induced layer depends on surface treatment method.