Effect of heating rate inα+γdual-phase field on lamellar microstructure and creep resistance of a TiAl alloy

Abstract

Abstract Lamellar microstructures of a Ti-48 mol.% Al alloy were varied by changing heating rate in the α + γ dual phase field, and their creep properties were investigated at 1150 K and 316 MPa. The minimum creep rate of the alloy first decreases and then increases with increasing the heating rate. Average spacing of α2 lamellae decreases and density of γ/α2-lamellar boundaries increases with increasing the heating rate. The high density of γ/α2 boundaries stabilizes the lamellar microstructure during creep, resulting in the decrease in the minimum creep rate. With increasing the heating rate, α2 lamellae are discontinuous and γ/α2 boundaries become less efficient in retarding recovery. This microstructural degradation results in the increase in creep rate at high heating rate. A reduction of creep rate by one order of magnitude from as-grown lamellar microstructure is achieved at the optimal heating rate.