Gibbs energy modelling of the driving forces and calculation of the fcc/hcp martensitic transformation temperatures in Fe-Mn and Fe-Mn-Si alloys

Very recent, accurate dilatometric measurements of the fcc<->hcp martensiti c transformation (MT) temperatures are used to develop a new thermodynamic description of the fee and hcp phases in the Fe-Mn-Si system, based on phen omenological models for the Gibbs energy function. The composition dependen ce of the driving forces for the fcc<->hcp and the hcp<->fcc MTs is establi shed. Detailed calculations of the MT temperatures are reported, which are used to investigate the systematic effects of Si additions upon the MT temp eratures of Fe-Mn alloys. A critical comparison with one of the most recent thermodynamic analyses of the Fe-Mn-Si system, which is due to Forsberg an d Agren, is also presented. (C) 1999 Elsevier Science S.A. All rights reser ved.