The impact of aging time on fracture mode of a metastable β alloy with network-like microstructure

Abstract

Metastable β alloys (Ti-5Al-2Sn-2Zr-4Cr-4Mo) with network-like microstructure were obtained by aging at 630 °C for 1–25 h, and subjected to the tensile fracture at room temperature. The obtained alloy (equiaxed α and precipitated α phases) has the high strength and good plasticity, which are comparable to those of near-β forged alloys. The tensile fracture mode of the short-time aging alloy is the ductile fracture with local long voids. The micro-cracks initiation at the grain boundary α layer and adjacent equiaxed α phases gives rise to the long voids. As the aging time increases up to 25 h, Al atoms penetrate within equiaxed α phase and Mo atoms pile up along the α/β interface. During the tensile process, the release of local stress is due to the α/β interface softening. The ductile fracture of the long-time aging alloy is determined by the void growth and coarsening.