Influence of preliminary deformation on structure and properties of Fe-Ni-V-C alloy after reverse α → γ transformation

Using transmission electron microscopy, the Fe-25 Ni-1.5 V-0.3 C alloy structure was investigated after the γ → α → γ transformation and the effect of the preliminary deformation upon it in the range from 16 to 33% at the temperature of +200 and -196 deg C. Characteristic of nondeformed specimens is the lath morphology of the reverse austenite. Deformation prior to the α → γ transformation is conducive to the appearance of areas of fine-grained austenite With a low density of dislocations, probably forming through a partial recrystallization of the lath austenite. It was found that the reverse austenite inherits the misorientation zones which are a structure particularity of slippage-deformed (259) martensite crystals (7). The maximum strength of the alloy after the α → γ transformation is achieved through a preliminary deformation at-196 deg C leading to a decrease in the amount of austenite that failed to undergo the γ → α → γ transformation