Microstructure and deformation behavior of Ti-6A1-4V alloy by high-power laser solid forming

This work investigated the microstructure and tensile deformation behavior of Ti-6A1-4V alloy fabricated using a high-power laser solid forming (LSF) additive manufacturing. The results show that the post fabricated heat-treated microstructure consists of coarse columnar prior-beta grains (630-1000 mu m wide) and alpha-laths (5-9 mu m) under different scanning velocities (900 and 1500 mm/min), which caused large elongation (similar to 18%) superior to the conventional laser additive manufacturing Ti-6A1-4V alloy. The deformation behavior of the LSF Ti-6A1-4V alloy was investigated using in situ tensile test scanning electron microscopy. The results show that shear-bands appeared along the alpha/beta interface and slip-bands occurred within the alpha-laths, which lead to cracks decaying in a zigzag-pattern in the LSF Ti-6A1-4V alloy with basket-weave microstructure. These results demonstrate that the small columnar prior-beta grains and fine basket-weave microstructure exhibiting more alpha/beta interfaces and alpha-laths can disperse the load and resist the deformation in the LSF Ti-6A1-4V components. In addition, a modified microstructure selection map of the LSF Ti-6A1-4V alloy was established, which can reasonably predict the microstructure evolution and relative grain size in the LSF process. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.