On the tensile embrittlement of lamellar Ti-5Al-5V-5Mo-3Cr alloy

In this paper, we investigated the tensile embrittlement of lamellar Ti-5553 alloy by analyzing its deformation mechanism, damage behavior and tensile fractography. The lamellar alloys were prepared by solution at 900 °C and ageing at 500 °C, 600 °C, 700 °C and 800 °C respectively. Although the lamellar alloys are different in the dimension and volume fraction of Alpha precipitation, they exhibit the same deformation, damage and fracture feature. The deformation of the alloy is dominated by the shearing of the Alpha precipitation and the simultaneous straining of the Beta matrix inside the lamellar unit, and the strain localization of lamellar unit may lead to the formation of the deformation band. The damage of the alloy initiates at the intrinsic ruptured Alpha precipitation. As the strain increases, the micro-crack may propagate inside the deformation band by the coalescence of the micro-void inside the lamellar unit. Once the crack reaches the critical length, the trans-granular shearing fracture takes place, leading to the final failure. In summary, the tensile embrittlement of lamellar Ti-5553 alloy is mainly caused by the strain localization of lamellar unit and the trans-granular shearing fracture.