Low cost porous Ti-6Al-4 V structures by additive manufacturing for orthopaedic applications

Abstract

Ti-based alloys have exceptional features such as super-elasticity, shape memory effect, superior bio-corrosion resistance, satisfactory Young's modulus, and brilliant bio-compatibility intended towards bio-implant usage. However, solid Ti alloys have higher mechanical strength and modulus of elasticity, hence porous structures have been used instead of solid Ti alloy to get similar results as compared to human bones. Extensive research has been done to produce porous Ti alloy scaffolds with a lower modulus of elasticity and higher compressive strength as a substitute for human bones by varying porosity and input parameters. Three different types of scaffolds (Tesseract, Star, and Octet) with 65 % porosity were modelled in Rhino 6 software and constructed through route of additive manufacturing (AM), notably Selective Laser Melting or SLM of Ti-6Al-4 V powders. Then microstructures, mechanical characteristics and porosities of the Ti alloy scaffolds were investigated. The compressive test of porous Ti-6Al-4 V scaffolds were conducted by INSTRON machine with load capacity ± 25 kN and from results it is found that the modulus of elasticity of Tesseract, Star and Octet scaffolds are 10.78 GPa, 9.29 GPa and 8.61 GPa respectively which are similar to human bones (3–30 GPa). This work primarily focuses on advantages and performances of porous titanium scaffolds to serve the needs of orthopaedic applications. Due to its higher heating rate and lower hold time, AM technologies, notably SLM, can also build scaffolds withnanoscale grain. The desired function is typically not realised by this strategy, which leads to inadequate compaction. The scaffolds made by SLM have a reasonably good pore structural accuracy but moderate mechanical strength. Star type scaffolds have a greater manufacturing ability than other scaffolds, with a smaller porosity percentage error.