Texture and microstructure characterization in laser additive manufactured Ti-6Al-2Zr-2Sn-3Mo-1.5Cr-2Nb titanium alloy

Laser additive manufacturing (LAM) is a novel manufacturing technique in which metal components can be fabricated layer by layer. In this study, a recently developed damage tolerance titanium alloy TC21 (Ti-6Al-2Zr-2Sn-3Mo-1.5Cr-2Nb) was deposited by LAM process. Texture and microstructure characterization have been investigated by XRD, SEM and EBSD. Prior beta grains texture analysis indicates that the (100) poles concentrate in build direction with a texture intensity about 18.7. During cooling down from beta phase field, the beta to alpha phase transformation follows the Burger orientation relationship and a pronounced variant selection occurred. Besides, morphology and scale of alpha phase are quite different along the build direction due to different thermal history. Very fine rib-like alpha phase with the length less than 2 mu m and acicular martensite alpha' can be obtained at the bottom and the top of the sample, respectively. In the middle position, distribution and morphology of alpha phase is quite uneven and the precipitation sequence of alpha phase is alpha(GB) -> alpha(WGB) -> alpha(WM) -> alpha(S). The reasons by which they formed are discussed. (C) 2015 Elsevier Ltd. All rights reserved.