Fe-31% Ni-0.2% C 합금(合金)의 오스폼드 마르텐사이트와 마르폼드 마르텐사이트의 역변태처리(逆變態處理)에 의한 강화효과(強化效果)

Effect of Strengthening by Reverse Transformation of Ausformed Martensite and Marformed Martensite of Fe-31% Ni-0.2% C Alloy

In this study, the ausformed martensite and marformed martensite obtained from austenite with various deformation degrees in Fe-31% Ni-0.2%C alloy were transformed to revesed austenite at $510^{\circ}C$ by cyclic reverse martensite transformation. The effect of prior deformation, the rapid heating rate of reversion and number of cyclic transformation on the microstructure, mechanical properties of reversed austenite were investigated. The reverse austenite transformation is accomplised by the mechanism of shear type transformation. The structure of reversed austenite formed from ausformed martensite and marformed martensite with high deformation degrees is a fine structure of nearly equiaed grain containg a high density of dislocation tangles and was largely affected by the prior deformation applied before reversal transformation. The strength of reversed austenite is more increased with of cyclic transformation especially it is strength at the first cyclic transformation. The yield stress of revesed austenite of ausformed martensite is lower than that of marformed martensite.