Thermo-mechanical characterisation of selective laser melted Ti-5Al-5Mo-5V-1Cr-1Fe alloy under high strain rate loadings

This paper investigates the thermo-mechanical response and failure behaviour of a selective laser melted (SLM) near- β Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) alloy under high strain rate loading. A series of dynamic compression tests were performed using a split Hopkinson pressure bar at various temperatures (293–1173 K) and strain rates (1000–5000 s −1 ). Optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were employed to analyse the microstructure of the specimens and fracture surfaces of failed specimens. The dynamic compression stress-strain response, strain rate effect, thermo-softening effect and work hardening effect were studied. The results showed strong temperature and strain rate dependency for SLM Ti-55511. Higher temperature led to an improved ductility for SLM Ti-55511 alloy, demonstrated by the higher number of elongated dimples on the fracture surface. A modified Johnson-Cook constitutive model was established to predict the thermo-mechanical behaviour of SLM Ti-55511 alloy. • Thermo-mechanical response of selective laser melted Ti-5Al-5Mo-5V-1Cr-1Fe alloy are characterised. • The SLM Ti-5Al-5Mo-5V-1Cr-1Fe alloy exhibits strong temperature and strain rate dependency. • A competitive interplay exists between strain or strain rate hardening and thermal softening. • With increasing temperatures, the ductile dimples evolved from a parabolic shape to elongated forms and equiaxed structures.