A novel method for measuring the phase transformation temperature and enhanced coercivity in cold-rolled MnAlCx (x = 0–5) alloys

Abstract

The temperature for phase transformation of ε → τ in Mn54Al46Cx (hereafter denoted by MnAlCx, x = 0–5) alloys was systematically studied by using the traditional thermal analysis method and a more precise magnetic measurement method developed in this work. The effect of carbon content and cold-rolling on the magnetic properties of the MnAlCx alloys was studied. The onset temperature of massive growth of τ- from ε-phase increases with increasing carbon content in MnAlCx. The carbon content has little effect on the onset temperature of displacive growth of ε → τ but has substantial effect on the displacive growth rate at certain temperature. Pure τ-MnAlCx with varied x was obtained by annealing the ε-phase at optimum temperatures determined by our method. The Curie temperature of the MnAlCx decreases significantly first and then increases slightly with increasing carbon content. The coercivity and the remanent magnetization of the as-prepared τ-MnAlCx increase with increasing x first and become stable at x > 3 and x > 4, respectively. A cold-rolling method was introduced in this work to enhance the magnetic properties of τ-MnAlCx. The coercivity and remanent magnetization of the τ-MnAl after cold-rolling were enhanced up to 4.3 times and 3.3 times, respectively. The coercivity of the cold-rolled τ-MnAlCx decreases with increasing x and becomes stable when x > 2. The remanent magnetization and saturation magnetization of the cold-rolled τ-MnAlCx vary little with x.