Abstract
The thermal stability of microstructures is crucial for determining the performance of alloys in extreme environments. In the present work, the microstructural evolution and precipitation behavior in a high Nb-containing Ti45Al8Nb alloy during thermal exposure at 950 °C were investigated. It was found that excess α2 phases in the as-cast microstructure were unstable and tended to decompose during thermal exposure. Hexagonal Ti2Al phases precipitated at lamellar interfaces and had a [11¯0]γ∥[112¯0]α2∥[112¯0]Ti2Al, (002)γ∥(11¯00)α2∥(11¯00)Ti2Al crystallographic orientation relationship (OR) with the matrix. Stacking faults (SFs) generated in α2 phases during the α2 → γ phase transformation provided favorable nucleation sites for Ti2Al phases.
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