The Effect of Gd Addition on Mechanical Properties and Microstructure Evolution during Hot Deformation of β-Solidified γ-TiAl Based Alloy

Abstract

The effect of Gd microalloying on the microstructure, mechanical behavior, and structural evolution during hot deformation in the (α₂ + γ) phase field has been investigated on two experimental β-solidifying alloys based on γ–TiAl – Ti–45Al–2V–1Nb–1Zr and Ti–45Al–2V–1Nb–1Zr–0.2Gd (at %). The addition of Gd led to a reduction in the average size of plate-like (α₂ + γ) colonies from 250 to 140 μm, and the inter-lamellar spacing decreased from 160 to 110 nm in the as-cast state. It was shown that the reduction in the average colony size resulted in a decrease in the yield strength and peak stresses during hot deformation, with this effect being more pronounced at lower deformation temperatures. Additionally, the introduction of Gd resulted in the fraction of recrystallized/spheroidized volume increase of the forming α₂/γ-phase grains/particles and also their size reduction.