Temperature Dependence of Lattice Parameters and fcc/fct/fco Transformations in Some Mn-Base Metastable γ-Phase Alloys

Abstract

Lattice parameters of quenched Mn_1−XFe_X (X=0.27–0.31), (Mn_1−XFe_X)_0.95Cu_0.05 (X=0.15–0.28), and (Mn_1−XCo_X)_0.95Cu_0.05 (X=0.05–0.19) alloys were measured at temperatures between 80 and 480 K. The Mn–Fe and Mn–Fe–Cu alloys transformed from fcc to fct(c⁄a<1) structure on cooling below a critical temperature which was equal to or lower than the Néel temperature. With increasing cobalt concentration, the Mn–Co–Cu alloys underwent on cooling fcc/fct(c⁄a<1), fcc/fct(c⁄a<1)/fco, fcc/fct(c⁄a>1)/fco, and fcc/fct(c⁄a>1) transformations. These lattice change behaviours were compared with those of In-base alloys.