TEMPERATURE DEPENDENCE OF LATTICE PARAMETERS AND fcc/fct/fco TRANSFORMATIONS IN SOME Mn-BASE METASTABLE gamma -PHASE ALLOYS.

Abstract

Lattice parameters of quenched Mn//1// minus //xFe//x (X equals 0. 27-0. 31), (Mn//1// minus //xFe//x)//0//. //9//5Cu//0//. //0//5 (X equals 0. 15-0. 28), and (Mn//1// minus //xCo//x)//0//. //9//5Cu//0//. //0//5 (X equals 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 less than 1) structure on cooling below a critical temperature which was equal to or lower than the Neel temperature. With increasing cobalt concentration, the Mn-Co-Cu alloys underwent on cooling fcc/fct)c/a less than 1), fcc/fct(c/a less than 1)/fco, fcc/fct(c/a greater than 1)/fco, and fcc/fct(c/a greater than 1) transformations. These lattice change behaviors are compared with those of In-base alloys.