Microstructural refinement mechanism by controlling heating process in multiphase materials with particular reference to γ-TiAl

Abstract

The microstructural refinement mechanism by controlling heating rate was investigated in TiAl alloys as an example of multiphase materials. During heating in the α+γ dual phase field of TiAl alloys, the phase transformation of γ to α takes place. The increase in heating rate raises the extent of superheating, leading to increases in driving force and the nucleation rate of the α phase. At higher heating rate, numerous α nuclei form and lengthen, resulting in a fine α2∕γ lamellar microstructure after subsequent cooling. The theoretical prediction was demonstrated by the experimental results obtained on a fully lamellar Ti-48Al alloy.