MAGNETIC AND TRANSPORT STUDIES OF THE ALPHA-SIGMA TRANSFORMATION IN FE54CR46 AND FE52CR46SN2 ALLOYS - KINETICS OF SIGMA-PHASE-FORMATION

The kinetics of the alpha-sigma isothermal transformation in Fe54Cr46 and Fe52Cr46Sn2 (at%) alloys was studied by magnetization (M) and Elec trical resistivity (rho) measurements at constant temperature, T = 973 K. The variations of the resistivity with temperature during heating or cooling are interpreted in terms of the magnetic and structural evo lutions of the alloys. The time dependence of the isothermal increase of rho and of the decrease of M follows Johnson-Mehl-type equations wi th similar kinetic coefficients. Magnetization and resistivity studies , and also in-situ transmission electron microscopy investigations, co nfirm that the presence of Sn retards the alpha-sigma transformation b y preventing the sigma phase nucleation at grain boundaries.