Different Magnetic Field Effects on the $\varepsilon- \tau$ Phase Transformation Between (Mn,Zn)–Al and Mn–Al–C

In-magnetic-field annealing (IFA) effects on Zn-modified Mn-Al and Mn-Al-C were investigated at the annealing temperature of 573 K, which was around their TC. Mn
₅₃
Zn
₂
Al
₄₅
showed the magnetic-field-induced acceleration of the phase transformation to L10-phase (τ-phase) and the suppression of that to nonferromagnetic equilibrium phase. For Mn
₅₅
Al
₄₅
C
₂
, IFA effects were not clearly detected. These different magnetic field effects were discussed by the difference of the mechanism in stabilization of τ-phase. It is found by a thermal analysis that the modification of Zn stabilized τ-phase against ε-phase, realizing acceleration of transformation to τ-phase. The addition of carbon stabilized ε-phase against τ-phase. The ineffectiveness of in-field annealing for Mn-Al-C is due to the stabilization of ε-phase and the reduction of the Curie temperature. The combination of Zn modification and IFA is realized to synthesize high fraction of τ-phase for short annealing time and low annealing temperature.