Influence of solution treatment on microstructure evolution of TC21 titanium alloy with near equiaxed β grains fabricated by laser additive manufacture

Laser additive manufacture (LAM) is a novel technique in which metal components can be fabricated layer by layer. In this paper, the effects of solution temperature and cooling rate on microstructure evolution of the LAMed TC21 titanium alloy which containing near equiaxed prior alpha grains were studied. The LAMed and solution treated samples were investigated by optical microscopy (OM), scanning election microscope (SEM) and X-ray diffractometer (XRD). The results indicate that both the alpha phase volume fraction and alpha laths width are affected by the solution temperature and cooling rate. Different microstructure characterization leads to different Vickers hardness values. However, the solution temperatures selected in this study have insignificant effects on the beta and alpha phase texture. The near equiaxed prior beta grains exhibits much weaker texture intensity than the typical columnar prior beta grains. The comparison of the calculated and measured alpha phase texture indicates that variant selection occurred during the solution treatment. The martensite alpha' phase precipitated during the layer by layer process shows weak variant selection tendency. (C) 2016 Elsevier B.V. All rights reserved.