Blocky and columnar microstructures and the influence on mechanical behaviors of a hot-pressed Nb–23Ti–15Al alloy

Abstract

Abstract The microstructure and mechanical behaviors of a hot-pressed Nb–23Ti–15Al (at.%) alloy have been investigated. The results indicate that with different hot-pressing temperatures, the alloy presents remarkably different microstructural morphologies: blocky microstructure or columnar microstructure. At lower hot-pressing temperature, the blocky δ phase is formed by the reaction of the metastable σ phase and the β phase; at higher hot-pressing temperature, the δ phase directly precipitates from the supersaturated β phase with preferred orientation relationships of [212]δ//[001]β and (02 1 ¯ )δ//(110)β to form columnar microstructure. The columnar microstructure leads to higher microhardness and better toughness, for the reason that the columnar microstructure could resist deformation of the alloy effectively, and impede initiation and propagation of cracks.