Microstructures and mechanical properties of powder injection molded Ti-6Al-4V/HA powder

Taguchi method with an L₉ orthogonal array was employed to investigate the sintered properties of Ti-6Al-4V/HA tensile bars produced by powder injection molding. The effects of sintering factors at the 90% significance level: sintering temperature (1050°C, 1100°C and 1150°C), heating rate (5°C/min, 7.5°C/min and 10°C/min), holding time (30, 45 and 60min) and cooling rate (5°C/min, 20°C/min and 40°C/min) were investigated. Results showed that sintering temperature, heating rate and cooling rate have significant effects on sintered properties, whereas the influence of holding time was insignificant. It was found that a sintering temperature of 1100°C, a heating rate of 7.5°C/min and a cooling rate of 5°C/min increased the relative density, Vicker's microhardness, flexural strength and flexural modulus. However, a further increment of sintering temperature to 1150°C did not show any discernable improvement in the relative density and Vicker's microhardness, but there was a slight increase of 0.6% and 0.9% in the flexural strength and flexural modulus, respectively. Mechanically strong Ti-6Al-4V/HA parts with an open porosity of around 50% were developed.