This study attempts to develop Ti-Nb alloys with elastic moduli that approach that of human bone. The experimental results reveal that the microstructure of a Ti-Nb alloy that contains 14 mass% Nb consists of and phases, with phase being the dominant one. The proportion of the phase decreases gradually as the Nb content increases, and the microstructure becomes completely the phase when the Nb content exceeds 34 mass%. Moreover, the ! phase can be detected using XRD and TEM in alloys with a Nb content from 30 to 34 mass%. Over the Nb range studied (14 to 40 mass%), the elastic modulus decreases from 14 to 26 mass% Nb, and then increases to a maximum at 34 mass% Nb, before falling again as Nb content is increased further. The elastic modulus of the Ti-Nb alloys is closely related to the microstructure (or Nb content) of the alloys. The fall in the elastic modulus with the increasing Nb content from 14 to 26 mass% is associated with a gradual decrease in the proportion of the phase in the microstructure, while the precipitation of the ! phase accounts for the increase in the elastic modulus over the intermediate range of Nb (30 to 34 mass%). The tensile strength of Ti-Nb alloys increases slightly from 14 to 26 mass% Nb, and then increases markedly with a Nb content of up to 34 mass%, before falling drastically as Nb content is increased further. A similar pattern was obtained for 0.2% proof stress, while the elongation vs. %Nb curve was just the reverse of the T.S. vs. %Nb curve, as expected. A Ti-Nb alloy with a relatively high Nb content (above 36 mass%) is preferred to other compositions for use in medical implants with a reduced stress shielding effect.

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A mathematical model is developed in this study to simulate the filling pattern in lost foam casting and validated by comparing the simulated results to the experimental measurements. A special treatment is devised to handle the unique problem of back-pressure generated due to the evaporation of polystyrene during filling in lost foam casting. Experiments are also conducted with thermocouples embedded in the pattern of lost foam casting. With the measured temperature data, filling pattern can be derived. The mathematical model is then tested on several lost foam castings, where experimental measurements are also conducted. As the simulated filling patterns are compared with the experimental measurements, good agreement is observed.

In the present investigation, the mechanical properties of TiNb alloys were modified by electrochemical treatment. The properties of the TiNb alloy specimens were determined by electrochemical measurement and material analyses. The effects of titanium hydride compounds on the formation of porous structural oxide film during electrochemical surface treatment are examined by XPS, TF-XRD and SEM. Oxide films are formed during anodization following cathodic pretreatments. TiH 1.971 is formed by cathodic pretreatment. The TiH 1.971 is directly dissolved following anodic treatment.Additionally, the porous TiNb that was formed by the dissolution of TiH 1.971 were modified to porous oxide films.Hydrogen charging is important in forming porous oxide films.Anodization following cathodic pretreatment not only yields a thick oxide film, but also produces porous structures.Implanting bioactive TiNb into a porous oxidation film promotes bone-interface contact, improving osseo/osetointegration.