Evolution of microstructural homogeneity in novel Ti-6Zr-5Fe alloy fabricated by selective laser melting

Selective laser melting (SLM) process belongs to a layer-by-layer additive manufacturing technology, which has different temperature gradients, cooling rates, and reheating treatment in different regions due to the variation of the thermal histories for different layers during SLM process. This work aims to study the microstructural homogeneity evolution of beta phases, such as size, morphology, distribution, crystallographic orientation, and phase composition in different regions of the SLM Ti-6Zr-5Fe near beta titanium alloy. The results indicate that the microstructure in different regions of SLM Ti-6Zr-5Fe alloy sample is quite different. The beta phase in the bottom area had the smallest size about 7.25 mu m, the beta phase in the side-top area had the largest size about 20.56 mu m. The beta phase in the side-middle and middle part had a lower aspect ratio of 1.52 and 1.59, the beta phase in the side bottom and top part had a larger aspect ratio of 1.93 and 1.92. Most of the beta phase in the side-bottom and top part had the 001 crystal orientation towards build direction and laser moving direction, the texture type in other regions was random. The alpha phase in the top of the SLM Ti-6Zr-5Fe sample had a smaller size than that in the middle and bottom of the sample. Meanwhile, the microhardness in the top of SLM Ti-6Zr-5Fe sample was higher than that in the middle and bottom of the sample. The temperature gradients, cooling rates, and reheating treatment play different leading roles in different regions of the SLM Ti-6Zr-5Fe alloy sample.