Effects of thermal cycling and plastic deformation upon the Gibbs energy barriers to martensitic transformation in Fe-Mn and Fe-Mn-Co alloys

In a previous study of the effect of thermal cycling (TC) upon the fcc/hcp martensitic transformation (MT) in the binary system Fe-Mn, we evaluated the so-called resistance-to-start-the-transformation energy (RSTE) by applying models for the Gibbs energy of the fee and hcp phases, and found a well defined pattern of variation as a function of the number of phase transformation cycles. In the first few cycles, the so-called promotion effects upon the MT were observed, but in the following cycles inhibition effects were predominant. In the presented work we further explore the applicability of our previous generalizations, by focusing on a ternary system: the Fe-Mn-Co system. We show that Co additions do not modify the pattern of variation of the RSTEs with the number of cycles. The effect of inducing plastic deformation (PD) of the fee phase on the MT temperatures is also studied and compared with the effect of TC. The inhibition effect caused by PD is qualitatively the same as that of TC, as hypothesized in our previous work. (C) 1999 Elsevier Science S.A. All rights reserved.