Study of the compression and wear-resistance properties of freeze-cast Ti and Ti-5W alloy foams for biomedical applications

Ti and Ti-5 wt% W alloy foams were produced by freeze-casting process and their mechanical behaviors were compared. The Ti-5W alloy foam showed a typical acicular Widmanstatten alpha/beta structure with most of the W dissolved in the beta phase. An electron-probe microanalysis revealed that approximately 2 wt% W was uniformly dissolved in the Ti matrix of Ti-5W alloy foam with few partially dissolved W particles. The compressive-yield strength of Ti-5W alloy foam (similar to 323 MPa) was approximately 20% higher than that of the Ti foam (similar to 256 MPa) owing to the solid-solution-strengthening effect of W in the Ti matrix, which also resulted in a dramatic improvement in the wear resistance of Ti-5W alloy foam. The compressive behaviors of the Ti and Ti-5W alloy foams were predicted by analytical models and compared with the experimental values. Compared with the Gibson-Ashby and cellular-lattice-structure-in-square-orientation models of porous materials, the orientation averaging method provided prediction results that are much more accurate in terms of both the Young's modulus and the yield strength of the Ti and Ti-5W alloy foams.