Effect of thermal debinding conditions on microstructure and mechanical properties of a biomedical Ti-15Nb-5Sn alloy prepared by material extrusion additive manufacturing (MEAM) process

Abstract

In this study, the effect of thermal debinding conditions on the microstructure and mechanical properties of porous Ti-15Nb-5Sn (at%) alloys fabricated by the Material Extrusion Additive Manufacturing (MEAM) process was systematically investigated. A heating rate of 0.5 °C/min during thermal debinding effectively prevented shape distortion and surface defects, thereby maintaining geometric stability of the as-printed specimens. Increasing the thermal debinding time reduced the residual binder (from 15.7 % to 2.8 %) and oxygen content (from 1.27 wt% to 0.60 wt%) and consequently promoted diffusion between elemental powders. This enhanced diffusion led to an increase in the area fraction of the β phase (from 64.2 % to 81.4 %) and a decrease in porosity (from 39.5 % to 35.6 %). In solution-treated (ST) specimens, area fraction of the β phase, porosity and oxygen content were identified as the major factors influencing the mechanical properties. These factors contributed to improved mechanical performance, including an increase in maximum recoverable strain (from 1.6 % to 3.1 %), elongation (from 5.0 % to 10.5 %), along with a decrease in elastic modulus (from 20.0 GPa to 4.6 GPa). All ST specimens exhibited mechanical properties comparable to or exceeding those of trabecular bone, indicating their suitability as biomaterials for load-bearing bone replacement applications.