Titanium Carbide Precipitation in Ti-22Nb Alloy Fabricated by Metal Injection Moulding

摘要

Metal injection moulding was applied to fabricate Ti-22Nb (wt. %) alloy as a low-modulus material intended for biomedical applications. Tensile test specimens were injection moulded, followed by debinding and sintering. The sintering was conducted at 1500 ℃ for 4 h under vacuum (10~(-3) Pa). Selected as-sintered Ti-22Nb samples were treated by hot isostatic pressing at 915 ℃ for 2h under a pressure of 100 MPa. 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 Ti_2C with a face-centered-cubic structure. The calculation of the phase diagram showed a significant decrease of carbon solubility in Ti-22Nb compared to that in Ti from 500 ℃ to 1500 ℃, contributing to the carbide precipitation in Ti-22Nb alloy. Due to the carbide precipitation, the as-HIPed Ti-22Nb alloy exhibited higher tensile strength but lower elongation compared to conventionally processed Ti-22Nb.