Phase stability and fcc/hcp martensitic transformation in Fe–Mn–Si alloys: Part I. Experimental study and systematics of the MS and AS temperatures

Abstract

This paper presents the first part of an experimental and thermodynamic study of the fcc/hcp relative phase stability and the fcc↔hcp Martensitic Transformation (MT) in the Fe–Mn–Si system. In the present work, the building up of an extensive experimental database is described in detail. Fe–Mn–Si alloys with 15 to 35 wt. % Mn and up to 6.5 wt. % Si are investigated. The fcc→hcp ( M S) and the hcp→fcc ( A S) MT temperatures are determined using a dilatometric technique. With this new information, the composition dependence of the M S and A S temperatures is established. A well defined picture of the systematics of the MT temperatures emerges from our measurements, which is critically compared with the recent calculations due to Forsberg and Ågren. The need for a new assessment of the fcc/hcp relative phase stability in Fe–Mn–Si alloys is emphasized.