Coherency strains influence on martensitic transformation of γ-Fe particles in compressed Cu-Fe alloy single crystals

摘要

Single crystals of a Cu-Fe alloy, which containedspherical γ-Fe particles, were compressed up to shear strain of0.17 in liquid nitrogen bath. In the process of straining thestructural (optical and TEM) observations in as-deformed andpost-deformation annealed samples were provided. Thesubstructure of deformed samples was characterized by slightlydeveloped cell structure and lack of distinct layer-likearrangements of dislocations. Three kinds of particles were found:coherent and semi-coherent f.c.c. γ-Fe and martensitlciytransformed b.c.c. α-Fe. The critical diameter for coherency losswas found to be 58 nm at the initial stage of deformationdecreasing with strain to 50nm. Thses values coincided with thetheoretical estimations. It was suggested that relaxation ofcoherency strains around γ- Fe particles by the generation ofinterface dislocations might occur prior to the martensitictransformation. This assumption might explain the particle sizedependency of martensitic transformation.