Correlation between microstructures and mechanical properties under tensile and compression tests of heat-treated Ti-6Al-4 V ELI alloy produced by additive manufacturing for biomedical applications

As both life expectancy and accidents rates increase around the world, also the number of orthopedic surgeries has growth significantly, together with the need for advances in materials and techniques in order to better produce implants. The Direct Metal Laser Sintering (DMLS) is an additive manufacturing process capable of producing complex geometries and customized parts. In this study, samples of Ti-6Al-4 V ELI alloy were produced by DMLS and heat-treated at 650 degrees C for 3 h (stress relieving), and at 850 degrees C, 950 degrees C and 1050 degrees C for 1 h, all followed by furnace cooling. The microstructural modifications were analyzed by optical microscopy, scanning electron microscopy and X-ray diffraction, and the mechanical properties were analyzed by tensile, compression and Vickers microhardness tests. It was found that the higher the temperature of heat treatment, the higher the ductility and the lower the mechanical strength, due to nucleation and growth of alpha and beta phases. In addition, the values of ductility found for compression tests were higher than for tensile tests, having a different behavior under tensile and compression loads. The heat-treated Ti-6Al-4 V ELI alloy at 950 degrees C and 1050 degrees C conditions presented the best relation of mechanical properties for use in implants, meeting the requirements of ASTM F136 and ASTM 3001 standards.