Selective laser melting of Ti–35Nb composite from elemental powder mixture: Microstructure, mechanical behavior and corrosion behavior
School of Engineering
The availability of alloyed powder feedstock and chemical inhomogeneity, which often occur when using elemental mixed powder, have been long-term concerns of selective laser melting (SLM) of metallic materials. In this work, a Ti–35Nb alloy (in wt.%) was manufactured using SLM from elemental mixed powder to study the microstructure, mechanical behavior, and corrosion properties of the resultant parts. Microstructural characterizations show that the SLM-produced Ti–35Nb is composed of fine near β phase dendrites and undissolved Nb particles, which produces in a relatively low Young's modulus (84.7 ± 1.2 GPa). The chemical homogeneity and microstructural homogeneity are improved by heat treatment, resulting in a more homogeneous microstructure and smaller Nb particles. The undissolved large Nb particles play an important role in the overall performance of the SLM-produced materials, because the boundaries of undissolved large Nb particles in the as-SLMed part act as initiation sites for slip bands. The compressive fracture mechanism illustrates the propagation, arrest and merge of shear bands, thereby revealing the effects on the yield strength and plasticity. The electrochemical experiments show the stable corrosion resistance of as-SLMed sample and the improved corrosion resistance of the heat-treated counterparts. This work sheds insight into the SLM of Ti–Nb powder mixtures for biomedical applications. In particular, the relatively low cost and easy manufacture of elemental powder as feedstock offer significant advantages to the additive manufacturing industry.