In situ synchrotron X-ray diffraction line-profile analysis of additively manufactured Ti−6Al−4V alloy under tensile deformation

^a Institute for Materials Research, Tohoku University, Sendai, Japan
^b Graduate School of Science and Engineering, Ibaraki University, Hitachi, Japan
^c Department of Materials and Environmental Engineering, National Institute of Technology, Sendai College, Natori, Japan
^d Japan Atomic Energy Agency, Sayo, Japan

^* k_yamanaka@imr.tohoku.ac.jp

Abstract

In this study, the tensile deformation behavior of an electron beam melted Ti−6Al−4V alloy was examined by in situ X-ray diffraction (XRD) line-profile analysis. The as-built Ti−6Al−4V alloy specimen showed a fine acicular microstructure that was produced through the decomposition of the α′-martensite during the post-melt exposure to high temperatures. Using high-energy synchrotron radiation, XRD line-profile analysis was successfully applied for examining the evolution of dislocation structures not only in the α-matrix but also in the nanosized, low-fraction β-phase precipitates located at the interfaces between the α-laths. The results indicated that the dislocation density was initially higher in the β-phase and an increased dislocation density with increasing applied tensile strain was quantitatively captured in each constitutive phase. It can be thus concluded that the EBM Ti−6Al−4V alloy undergoes a cooperative plastic deformation between the constituent phases in the duplex microstructure. These results also suggested that XRD line-profile analysis combined with highenergy synchrotron XRD measurements can be utilized as a powerful tool for characterizing duplex microstructures in titanium alloys.