Microstructure-Property Evolution in Cold-Worked Equiatomic Fe-Pd During Isothermal Annealing at 500°C

Abstract

This chapter discusses the evolution of magnetic properties and microstructure in cold-deformed equiatomic Fe-Pd during isothermal annealing at 500℃. The magnetic age hardening behavior has been determined using a vibrating sample magnetometer. The microstructures have been characterized by a combination of X-ray diffraction (XRD), scanning and transmission electron microscopy (TEM) experiments. During annealing of the cold-deformed Fe-Pd concomitant re-crystallization and ordering produces a complex microstructure that exhibits enhanced coercivity relative to conventionally processed material. The maximum coercivity observed here was associated with a partially re-crystallized or combined reaction transformed microstructure. The magnetic age hardening behavior of the combined reaciton processed Fe-Pd has been attributed to a grain size hardening effect. The experimentally observed micro structural evolution of the cold-deformed Fe-Pd during annealing has been rationalized in terms of the competition between the combined reaction mode, which is associated with the discontinuous mode of ordering, and the continuous ordering transformation. The release of the stored strain energy during annealing of the cold-deformed Fe-Pd appears to accelerate the kinetics of a discontinuous ordering mode with respect to those of the usually dominant continuous ordering mode.