Microstructural homogenization through laser remelting in an additively manufactured Ti–40Nb sample from elemental feedstock powders
Shangavi Subramanian, Mayank Yadav, J. Jayaraj, Fan Yangyang, Lixia Xi, Konda Gokuldoss Prashanth
Abstract
Ti–Nb alloy fabricated via selective laser melting (SLM) serves as a promising candidate for orthopedic implants due to its exceptional biocompatibility and ability to mitigate stress-shielding effects. However, processing of in-situ alloyed Ti-Nb powder results in non-homogeneous microstructures and incomplete melting and diffusion of Nb hindering material homogeneity. In this study a laser remelting strategy was employed to enhance microstructural homogenization, Nb diffusion, and defect reduction. The effect of the cooling rate on the microstructure and mechanical properties of the resultant samples was explored. X-ray diffraction confirmed the presence of α′+β phase in single and triple melted samples. Remelted samples exhibited superior microstructural uniformity, reduced porosity, larger grain size, and increased α′ martensite morphology as confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM analysis shows reduced dislocation density and twins upon remelting. The mechanical properties of the remelted sample maintained a desirable combination of low modulus and high strength with a hardness of 368±7 HV, yield strength of 820±35 MPa, compressive strength of 1480±50 MPa, and an elastic modulus of 33±3 GPa. This work proves laser remelting is an effective strategy for fabricating Ti-40Nb alloy from elemental powder contributing to the development of orthopedic implants.