Abstract
In this study, Ti-(0-30 wt.%)Nb alloys developed from elemental powders were fabricated by the Selective Laser Melting (SLM) process. Compositional homogeneity, microstructure and mechanical performance were investigated as a function of energy density. The proportion of un-melted Nb particles and isolated pore count reduced with increasing energy density, while Ti allotropic content (i.e. α’, α” and β) varied with energy density due to in-situ alloying. Increasing the Nb content led to the stabilisation of the α” and β phases. The mechanical properties were similar to those compositions manufactured using casting methods, without further post processing. The addition of 20Nb (wt.%) and using an energy density of 230 J/mm3 resulted in a Young’s Modulus of 65.2 ± 1.8 GPa, a yield strength of 769 ± 36 MPa and a microstructure of predominantly α” martensite. This strength to stiffness ratio (33% higher than Ti-10Nb and 22% higher than Ti-30Nb), is attributed to in-situ alloying that promotes solid solution strengthening and homogenisation. These alloys are strong contenders as materials suitable for implantable load-bearing orthopaedic applications.
Highlights
Titanium and its alloys have characteristics, such as low density, corrosion resistance and non-toxicity for in vivo applications, making them ideal materials for use in orthopaedics and tissue engineering
Selective Laser Melting (SLM), which uses a laser to melt powder in layers to build the required part, can manufacture customised orthopaedic implants of complex geometries, with lowered investment cost and reduced machine time compared to traditional processes such as casting (Ref 9,10)
The application of this process has been dominated by industrially attractive alloys, such as Ti-6Al-4V, a a+b phase alloy, with few investigating b stabilised titanium alloys, such as Ti-Nb alloys (Ref 11-13)
Summary
Titanium and its alloys have characteristics, such as low density, corrosion resistance and non-toxicity for in vivo applications, making them ideal materials for use in orthopaedics and tissue engineering. Selective Laser Melting (SLM), which uses a laser to melt powder in layers to build the required part, can manufacture customised orthopaedic implants of complex geometries, with lowered investment cost and reduced machine time compared to traditional processes such as casting (Ref 9,10). The application of this process has been dominated by industrially attractive alloys, such as Ti-6Al-4V, a a+b phase alloy, with few investigating b stabilised titanium alloys, such as Ti-Nb alloys (Ref 11-13). The phases, microstructural evolution, homogeneity, and mechanical properties of these alloys were investigated with respect to those produced using conventional methods, such as vacuum cast re-melting
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