Microplasticity of amorphous and crystallized Fe$_{78}$P$_{20}$Si$_{2}$ alloy

With the aim of establishing the mechanism of plastic deformation the local hardness and plasticity of the amorphous alloy (AA) Fe$_{78}$P$_{20}$Si$_{2}$ at different stages of its crystallization, thermal annealing (TA) at 300–750$^\circ$С or short-term photonic treatment (PT) with the dose received at the sample radiation of 10–60 J/cm$^{-2}$ is mapped. The phase composition and structure were investigated by x-ray diffractometry and high-resolution transmission electron microscopy. With a general sequence of structural changes, the crystallization rate at the PT is more than two orders of magnitude greater than TA that indicates the effect of a high rate of input of the activation energy of the process. The nonmonotonic dependence of hardness, modulus of elasticity and the proportion of plastic deformation in the work of indentation depending on the annealing temperature or the dose of radiation entering the sample as a result of structural changes in the alloy was established. In this case, the local plasticity of the initial alloy and the fully crystallized one are close in magnitude. Based on the features of the crystal structure of the Fe$_3$P phase (respectively, the impossibility of the dislocation mechanism of plastic deformation) and on the assumption of the identity of the structural unit (tetrahedral cluster Fe$_3$P) of the crystallized and amorphous alloy, the conclusion about the cluster mechanism of plastic deformation of the as is formulated.