Effects of Thermal Cycling on the Fcc/Hcp Martensitic Transformation Temperatures in Fe-Mn Alloys

A. BARUJ; S. COTES; M. SADE; A. FERNÁNDEZ GUILLERMET

ZEITSCHRIFT FUR METALLKUNDE

Carl Hanser Verlag

Lugar: Munich; Año: 1996 vol. 87 p. 765 - 772

0044-3093

A systematic study has been performed of the effect of thermal cycling (TC) upon the fcc/hcp martensitic transformation (MT) temperatures in the Fe-Mn system. The experimental part of the work comprises TC experiments on alloys with Mn contents between about 16 and 30wt%, and the determination of the Ms and As temperatures by dilatometric techniques. These data are analysed thermodynamically using Gibbs energy functions for the fcc and hcp phases. The driving forces for the start of the fcc/hcp and the hcp/fcc transformations are studied as functions of composition and the number of thermal cycles. The analysis reveals significant regularities, which points to the existence of both promotion and inhibition effects of TC upon the fcc/hcp MT. These effects are discussed in the light of the available information on the MT in Fe-Mn and related systems. A possible microstructural picture is developed which recognizes the key role of stacking faults and other crystalline defects in the nucleation and growth processes in this MT.