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

Highlights: • A method to measure the phase transformation temperature of MnAl-C is reported. • A cold-rolling method is employed to enhance the magnetic properties of MnAl-C. • The phase transformation temperature increases with increasing carbon content. The temperature for phase transformation of ε → τ in Mn₅₄Al₄₆C_x (hereafter denoted by MnAlC_x, 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 MnAlC_x alloys was studied. The onset temperature of massive growth of τ- from ε-phase increases with increasing carbon content in MnAlC_x. 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-MnAlC_x with varied x was obtained by annealing the ε-phase at optimum temperatures determined by our method. The Curie temperature of the MnAlC_x decreases significantly first and then increases slightly with increasing carbon content. The coercivity and the remanent magnetization of the as-prepared τ-MnAlC_x 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-MnAlC_x. 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-MnAlC_x decreases with increasing x and becomes stable when x > 2. The remanent magnetization and saturation magnetization of the cold-rolled τ-MnAlC_x vary little with x.