Metal injection moulding of non-spherical titanium powders: Processing, microstructure and mechanical properties

The critical processing parameters for metal injection moulding (MIM) of titanium using inexpensive non-spherical hydride-dehydride (HDH) powders with an average particle size of 45 μm were established through a series of laboratory scale injection moulding investigations. A slow heating rate of 1.0 K/min during thermal de-binding and sintering resulted in samples with negligible or limited distortion and nearly uniform shrinkage in all directions. Sintering at 1250 °C for 120 min was identified to be a suitable condition for MIM of HDH Ti, which produced samples with a relative density of 96.5%, uniform shrinkage of 13.9% along the length direction and 14.7% along the thickness direction. The as-sintered samples achieved a tensile strength of 395 MPa and elongation of 12.5%. The promising tensile elongation indicates that MIM of HDH titanium powder can cope with the relatively high oxygen level in the initial inexpensive HDH Ti powder as well as the unavoidable further increase in oxygen level during the MIM cycle.