Porous NiTi alloy by metal injection moulding/sintering of elemental powders: Effect of sintering temperature

With the potential to display pseudoelasticity and the shape memory effect, porous NiTi is promising for biomedical implant applications. Here, open porous NiTi is fabricated by metal injection moulding (MIM) of elemental Ni and Ti powders, followed by thermal debinding and transient liquid phase (TLP) sintering. The material produced has porosity of 39–45% and average pore size 100–120 μm. A sintering temperature above 1050 °C is needed to allow sufficient interdiffusion to have substantially NiTi (B2) phase and avoid phases such as NiTi2 and Ni3Ti with poor mechanical properties, and at 1250 °C sintering reduces the amount and size of porosity.

► We study a new process of porous NiTi for bone implant using Ni and Ti powders.
► Binder materials in metal injection moulding (MIM) can be treated as pore former.
► Transient liquid phase sintering enables greater fraction of porous structure.
► Expansion after sintering is nearly uniform (3–7%), unlike compaction/sintering.
► Major fraction of B2 (NiTi) phase is developed at temperatures above 1050 °C.