Regularities of the Formation of the Structure of Rapidly Quenched Powder of a Heat-Resistant Ti-Based Alloy Produced by PREP Method

Abstract

A multiscale study of the structure of spherical particles (granules) of rapidly quenched powder of a heat-resistant (α + β) titanium-based alloy obtained by the PREP method, which has been subsequently used for the manufacture of products using PM HIP technology, has been carried out. Metallography LM, SEM, EDX, OIM methods are used to study the structure of granules of different sizes. The influence of the granule size and vacuum heat treatment at temperatures in the fields of the (α + β) and β phases on the regularities of the formation of the microstructure of granules has been revealed. The dendrite microstructure of grains of the metastable β phase has been found in the particles (granules) of the original rapidly quenched PREP powder. Dendrite segregation of alloying elements is clearly revealed in larger particles, for example, for Mo. In smaller particles, the formation of a more highly dispersed structure has been observed. The effect of granule size decreasing on the reduction of the size parameter of the dendritic structure (SDAS) has been determined. Schematic TTT diagrams of phase transformations in the studied alloy, including crystallization, martensitic transformation, and normal diffusion transformation β → (α + β), have been constructed.