Effect of Applied Pressure on Microstructure and Mechanical Properties for Spark Plasma Sintered Titanium from CP-Ti Powders

The aim of this study was to determine the effect of applied pressure and sintering temperature on the microstructure and mechanical properties for spark plasma sintering (SPS) from commercial pure titanium (CP-Ti) powders. Spark plasma sintering is a relatively new sintering technique in powder metallurgy which is capable of sintering metal and ceramic powers quickly to full density at a fairly low temperature due to its unique features. SPS of -200 mesh or -400 mesh CP-Ti powders was carried out in an Ar+H-2 mixed gas flowing atmosphere between 650 degrees C and 750 degrees C under 10 to 80 MPa pressure. When SPS was carried out at relatively low temperatures (650 degrees C to 750 degrees C), the high (>60 MPa) pressure had a marked effect on densification and grain growth suppression. The full density of titanium was achieved at temperatures and pressures above 700 degrees C and 60 MPa by spark plasma sintering. The crystalline phase and microstructure of titanium sintered up to 700 degrees C consisted of alpha-Ti and equiaxed grains. Vickers hardness ranging from 293 to 362 Hv and strength ranging from 304 to 410 MPa were achieved for spark plasma sintered titanium.