等原子組成のFe-V合金におけるσ相の生成挙動

Abstract

The electrical resistivity and acoustic emission (AE) were measured simultaneously during a cyclic heat treatment from room temperature either to 973 K or 873 K, in order to study the mechanisms of sigma phase formation in an equiatomic Fe-V alloy. During the holding stage for 432 ks either at 973 K or 873 K, the 973 K specimen produced drastic increase both in the resistivity and the AE event count, but the 873 K specimen produced a considerable amount of AE but a slight decrease in the resistivity. The occurrence of the AE took place not continuously but intermittently during the holding stage at those temperatures. Furthermore, examinations by X-ray analysis and transmission electron microscopy showed that the 973 K specimen consisted entirely of the sigma phase containing many lattice defects, and that the 873 K specimen consisted mainly of the ferrite phase and slightly of the sigma phase which was confined to an extremely thin layer on the free surface.On the basis of the concept that the AE occurrence and introduction of lattice defects may be restricted to the diffusionless transformation, it was inferred that the cooperative movement of atoms takes part in the sigma phase formation in the equiatomic Fe-V alloy.