Microplasticity of Amorphous and Crystallized Fe78P20Si2 Alloy

Abstract

In order to determine the mechanism of plastic deformation, the hardness and local plasticity of amorphous Fe₇₈P₂₀Si₂ alloy are compared at different stages of its crystallization activated by thermal treatment at 300–750°C or short-term photon treatment with a radiation dose coming to the sample of 10–60 J/cm². The phase composition and structure were investigated by X-ray diffractometry and high-resolution transmission electron microscopy. With the same sequence of structural changes, the crystallization rate under photon treatment is more than two orders of magnitude higher than that under thermal treatment, which indicates the effect of a high rate of input of the process activation energy. The nonmonotonic dependence of the hardness, elastic modulus, and the proportion of plastic strain in the indentation work is found, depending on the annealing temperature or radiation dose received by the sample, as a result of structural changes in the alloy. The local plasticity of the initial alloy and fully crystallized alloy are close in magnitude. Based on the features of the crystal structure of the Fe₃P phase (the impossibility of the dislocation mechanism of plastic deformation) and assuming that the structural unit (tetrahedral Fe₃P cluster) of the crystallized and amorphous alloy is identical, a conclusion was formulated about the cluster mechanism of plastic deformation of the amorphous alloy.