Austenite ferromagnetism and martensite morphology

Abstract

The Curie temperature of the austenite, the martensite-start temperature, and martensite morphology have been determined in a series of nil-carbon Fe−Ni and Fe−Ni−Co alloys. For these alloys, austenite ferromagnetism aboveMs is a necessary, but not sufficient, condition for the formation of lenticular rather than packet martensite. In contrast to Fe−Ni alloys where lenticular martensite only forms below ≈O°C, some of the Fe−Ni−Co alloys transform to this structure at temperatures up to ≈200°C. The results support the hypothesis that the resistance of austenite to plastic deformation affects the habit plane and thus morphology of the martensite which forms.