Titanium carbide precipitation in Ti-22Nb alloy fabricated by metal injection moulding

Metal injection moulding was applied to fabricate Ti-22Nb alloy as a low modulus material for biomedical applications. Tensile test specimens were injection moulded, followed by debinding and sintering. Sintering was at 1500 degrees C for 4 h under vacuum (10(-3) Pa). Selected as-sintered Ti-22Nb samples were hot isostatically pressed at 915 degrees C/100 MPa for 2 h. The nature of the titanium carbide precipitates in the as-sintered Ti-22Nb alloy was investigated. Selected area electron diffraction patterns revealed that the carbides are Ti2C with a fcc structure. The calculation of the phase diagram showed a significant decrease of carbon solubility in Ti-22Nb compared with that in Ti from 500 to 1500 degrees C, contributing to the carbide precipitation in Ti-22Nb. Due to the carbide precipitation, the as-hipped Ti-22Nb alloy exhibited higher tensile strength but lower elongation than conventionally processed Ti-22Nb.