The effect of cellular reaction on mechanical behavior and microstructure evolution of β-solidified γ-TiAl based alloy during hot deformation

Abstract

In this work, the effect of cellular reaction on the mechanical behavior and evolution of the microstructure of the Ti-43.2Al-1.9V-1.1Nb-1.0Zr-0.2Gd-0.2B (at.%) alloy during uniaxial compression at Т = 1050 °C, έ = 10⁻³ s⁻¹ and ɛ = 70 %. The lamellar (HT1) and metastable α₂-grain (HT2) initial structures were produced by heat treatment and used as starting materials. Heating to the deformation temperature of the HT1 condition has not resulted in any noticeable changes in the microstructure, while HT2 microstructure transforms to (α₂+γ) nanolamellar colonies alongside with development of a cellular reaction with the formation of coarse lamellar colonies. In the HT2 state, compared to HT1, the flow stresses are significantly reduced and the nature of the mechanical behavior changes. This behavior was associated with the localization of plastic flow in coarse lamellar colonies, and the development of recrystallization and spheroidization processes in them. By the final stage of deformation, the proportion of recrystallized/spheroidized structure increases in the HT2 state to 87 %, while in HT1 it is only 50 %. Mechanical behavior, structural evolution, and plastic deformation mechanisms are discussed.