The effect of post-sintering heat treatments on the tensile properties of Ti-6A1-4V alloy.

Previous studies have shown that the application of a porous coating to a solid substrate offers several advantages over current methods of implant fixation. However, the heat treatments required to sinter porous metal coatings have also been shown to cause significant decreases in the mechanical properties of the substrate. With Ti-6A1-4V alloy, sintering above the material beta transus results in a transformation from the as-received, equiaxed microstructure, recommended for surgical implants, to a lamellar alpha-beta microstructure. This lamellar structure has been shown to have inferior mechanical properties. In the present study, microstructural analysis and mechanical testing were performed on Ti-6A1-4V alloy subjected to various post-sintering heat treatments in an attempt to improve the mechanical properties. The microstructures examined were a fine and a coarse acicular alpha in a retained beta matrix. Tensile tests were performed on specimens containing these structures and results were compared with the lamellar and equiaxed microstructures. The fine acicular alpha structure was shown to exhibit the best tensile properties for the post-sintering Ti-6A1-4V alloy microstructures examined, displaying a 9.8% elongation value, as compared to the as-received, equiaxed microstructure value of 13.5%. This represents a significant improvement over the 5.1% value obtained with the lamellar microstructure.