Transgranular shearing introduced brittlement of Ti–5Al–5V–5Mo–3Cr alloy with full lamellar structure at room temperature

Abstract

β titanium alloys with full lamellar structure often exhibit the low elongation, and the brittle fracture mechanism of Ti–5Al–5V–5Mo–3Cr β titanium alloy with full lamellar microstructure is investigated in this paper. After tensile test, the fracture surface characterization and the cross sectional observation show that the transgranular dimple fracture, the intergranular fracture and the transgranular shearing fracture are the fracture mode of the alloy. It is discovered that the cracks form by the coalescence of the microvoid at the α/β interfaces, and the shearing is triggered by the gradual increment of the crack dimension inside the prior β grain at a high stress level. The first two fracture progresses contribute to the plastic deformation of the alloy, and the transgranular shearing occurs in the large scale β grain and is the main brittle fracture mechanism of Ti-5553 alloy.