In-situ investigation into the deformation behavior of Ti-6Al-4V processed by laser powder bed fusion

Abstract

In this work, we presented an investigation into the deformation behavior of laser powder bed fusion (LPBF) Ti-6Al-4 V (Ti64), particularly how microstructure characteristics determined the grain deformation behavior by using in-situ SEM tensile characterization. Results demonstrated that α laths with their elongation directions 45° to the tensile loading axis and α laths with the larger thickness could induce severe strain accumulation during the uniaxial tensile process. Crystallographic orientations and grain morphologies of α lath were considered the key factors that could influence the deformation behavior. The strain localization was observed in the α laths dominated by multiple slip systems. Furthermore, the α laths with their elongation directions 45° to the tensile loading axis had the longest effective slip length, which could make α laths favorable for deformation. The dislocations multiplication of coarse α laths was much greater than in fine α laths, which could also result in strain localization. These findings could shed light on the deformation behavior related to lamellar structure in LPBF Ti64 and could further help the mechanical property manipulation. • Strain distribution of LPBF Ti64 during the tensile process was characterized by using in-situ SEM tensile testing • Crystallographic orientations and grain morphologies of α lath were considered the key factors that could determine the deformation behavior • The strain localization was observed in the α laths dominated by both prismatic <a > and pyramidal <c + a > slip systems • The α laths with elongation directions 45° to the tensile loading axis have the longest effective slip length, which could make them favorable for deformation • The dislocations multiplication of coarser α laths is more rapid than in fine α laths, which could also result in strain localization