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The microstructures, mechanical properties, and biocompatibilities of as-solutionized Zr-Nb system alloys with different Nb contents for biomedical applications were investigated. The microstructures of Zr-5 mass%Nb, Zr-10 mass%Nb, and Zr-20 mass%Nb alloys subjected to solution treatment (ST) consist of α′, ω, and β phases while the microstructure of Zr-30 mass%Nb alloy subjected to ST consists of almost all single β phase. Young's modulus of Zr-20 mass%Nb alloy shows the lowest value of 63 GPa among the others alloys although the tensile strength and 0.2% proof stress decrease because of decrease in volume fraction of ω phase while Zr-10 mass%Nb alloy with a large amount of ω phase shows the highest values of Young's modulus, tensile strength, and 0.2% proof stress. The elongations of Zr-20 mass%Nb and Zr-30 mass%Nb alloys show relatively high values of 22% and 24%, respectively. The cell viability and bone-bonding characteristics of Zr-Nb system alloys are improved with increasing Nb content. Therefore, it is considered that Zr-Nb alloys have relatively high biocompatibility and belong to bio-inert metallic biomaterial.

The cost of titanium (Ti) and its alloys is still much higher than the costs of steels and aluminum alloys; this has inhibited their widespread usage. It is necessary to reduce their cost in order to make Ti and its alloys common metallic materials, namely, ubiquitous titanium and its alloys for their widespread usage. One of the main reasons for their high cost is that they contain a large amount of high-cost rare metals. Therefore, it is imperative to conduct research and development for producing Ti alloys that utilize low-cost common metal elements such as Si, Al, Fe, Cu, and Sn and interstitial elements such as O, N, H, and C. In this paper, the effects of ubiquitous alloying elements such as interstitial elements, O, N, C, and H, and substitutional elements, Fe and Si, which have been generally treated as impurities on functionalities of titanium alloys are discussed.

The frictional wear characteristics, mechanical properties, and biocompatibilities of biomedical Zr-20 mass%Nb alloy (Zr-20Nb) subjected to solution treatment (ST) and air-oxidizing process (AOP) were investigated. Vickers hardness of the specimen surface of Zr-20Nb subjected to AOP at 973 K, 1073 K, and 1123 K are approximately 4.5 times larger than that of Zr-20Nb subjected to ST. Young's modulus of Zr-20Nb subjected to AOP increases with increasing AOP temperature up to 1073 K. 0.2% proof stress, tensile strength, and elongation of Zr-20Nb subjected to each AOP decrease proportionally with increasing AOP temperature, and is inferior to those of Zr-20Nb subjected to ST because of the growth of oxide layer with a large amount of micro-cracks and the diffusion of oxygen into the subsurface. Frictional wear loss of Zr-20Nb subjected to each AOP decreases drastically as compared to that of Zr-20Nb subjected to ST. Bone-compatibility of Zr-20Nb subjected to AOP at 973 K is better than that of AOP at 1073 K because of the existence of some cracks and partial exfoliation of oxide layer.

The purpose in this study is to investigate the effect of microstructure on the unique hardening behavior of dental silver alloy, Ag-20Pd-14.5Cu-12Au (mass%), fabricated by hot rolling process (AS material), which is in as-received condition, and liquid rapid solidification (LRS) process (LRS material). The following results were obtained. The microstructure of AS material is consisted of α1, α, and β phases. The microstructure of AS material changes to α, β, and β′ phases through a solution treatment (ST). The microstructure of LRS material is consisted of α, α1, and α2 phases without β phase. The microstructure of LRS material becomes single α phase through ST. Relatively large β phases with the diameter of tens of μm on AS material coarsen according to increasing the ST time, while the small those with the diameter of a few μm are solid-soluted into the matrix. On the other hand, the coherent participation of β′ phases with long and short axes of around 100 nm and 10 nm, respectively, also occurs during ST although the amount of β′ phase decreases with increasing the ST time. The hardness and tensile strength of LRS material and LRS material subjected to ST are relatively smaller than those of AS material and AS material subjected to the same treatment. From this results, the effect of solid solution hardening of α, α1, and α2 phases is lower than that of precipitation hardening of β′ phases. In a case of the unique hardening seems to occur because the precipitation of β′ phases are enhanced during ST.

The effect of oxygen content on the microstructure and mechanical properties of Ti-29Nb-13Ta-4.6Zr (TNTZ) solutionized and aged at 723 K was investigated. The microstructure of solutionized TNTZ consists of a single β phase, and addition of oxygen leads to the increase in the hardness and tensile strength because of solid solution hardening, and the increase in Young's modulus, and the decrease in the elongation. On the other hand, the α phase precipitates in the aged TNTZ. The results of transmission electron microscopy and X-ray diffraction imply that the size and volume fraction of the α phase increase with the oxygen content in the aged TNTZ. The mechanical properties of the aged TNTZ change with the oxygen content. Age hardening in aged TNTZ is enhanced by an increase in the oxygen content. Further, with an increase in the oxygen content, both the tensile strength and Young's modulus increase, while elongation decreases due to the precipitation of the α phase. TNTZ with different mechanical properties (Young's modulus: around 60-100 GPa, tensile strength: around 600-1400 MPa, elongation: around 5-25%) can be obtained depending on the oxygen content and the heat treatment technique.

In recent years, the opportunity of the hard tissues such as bones, hip joints and tooth to be replaced by metallic biomaterials is increasing. In general, metallic biomaterials lack bioactivity, which is the ability to directly form a chemical bond with bones. Therefore, the bioactive surface modifications on surface of metallic biomaterials have been investigated and applied. Among them, the calcium phosphate invert glass coating method, which is dip-coating treatment (DCT), can be granted the bioactivity on the surface of a β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy, for biomaterial applications. In this study, aging characteristics and mechanical properties of TNTZ alloy surface-modified with DCT were investigated. There is an oxide layer and α case near boundary between calcium phosphate invert glass layer and TNTZ surface in TNTZ surface-modified with DCT (TNTZDCT). A very fine ω phase precipitates in an equiaxed β phase with an average diameter of 20 μm at a distance of 200 μm from specimen surface. On the other hand, the microstructure of aged TNTZDCT has an α phase. The tensile strength of TNTZDCT is around 30% greater than that of as-solutionized TNTZ (TNTZST). On the other hand, the elongation is around 48% smaller than that of TNTZST. Tensile strength of aged TNTZDCT is around 26% greater than that of TNTZDCT. While the elongation of aged TNTZDCT is around 52% smaller than that of TNTZDCT. Fatigue limit of TNTZDCT is nearly equal to that of TNTZST. Fatigue limit of aged TNTZDCT is around 80 MPa greater than that of TNTZST. Fatigue limits of TNTZDCT and aged TNTZDCT, where their fatigue specimen surfaces are mirror-polished, rise as compared with those of TNTZDCT and aged TNTZDCT, where their fagigue specimen surfaces are shot-blasted.

Tensile tests and static fracture toughness tests were carried out on variously heat-treated type IV gold alloys. The effects of microstructures on tensile characteristics and static fracture toughness were discussed. The tensile strength of type IV gold alloy increases with increasing solutionizing temperature. Moreover, the tensile strength of type IV gold alloy increases with increasing ageing time when the solutionizing temperature is 1023 K. While the elongation of type IV gold alloy decreases with increasing solutionizing temperature. Static fracture toughness of type IV gold alloy increases with increasing solutionizing temperature. Static fracture toughness of type IV gold alloy of aged for 0.3 ks is the greatest, and that of aged for 1.8 ks is the smallest when the solutionizing temperature is 1023 K.

Ti-XNb-10Ta-5Zr alloys were fabricated based on Ti-30Nb-10Ta-5Zr alloy, which was the composition that simplified that of Ti-29Nb-13Ta-4.6Zr alloy for biomedical applications. The tensile deformation mechanisms of the Ti-25Nb-10Ta-5Zr, Ti-30Nb-10Ta-5Zr, and Ti-35Nb-10Ta-5Zr alloys were investigated using X-ray diffraction analysis under several loading conditions. Under loading conditions, the X-ray diffraction peaks of all specimens in this study shift to higher angles than those obtained under non-loading conditions. In the crystal orientation of Ti-30Nb-10Ta-5Zr alloy, in which the lattice strain has reached the maximum elastic lattice strain, plastic deformation (for example slip) is moved with elastic deformation. Therefore, the elastic modulus of this alloy appears to decrease in terms of strain over a proportional limit. Thus, the elastic deformation behavior of the Ti-30Nb-10Ta-5Zr alloy does not obey Hooke's law.

A novel method of preparing a calcium phosphate glass coating on a metallic titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), was developed by CO2 laser irradiation. It was difficult to melt 60CaO-30P2O5-3TiO2-7Na2O (mol%) glass powders dip-coated on TNTZ for joining by the irradiation of 5 W power. After a trace amount of sodium phosphate was dispersed between the glass particles on TNTZ, the CO2 laser was irradiated to the surface; sodium phosphate was melted by the irradiation to react with the surfaces of the glass particles and with the thin oxide layer on TNTZ, resulting in the formation of a strong calcium phosphate glass coating on the substrate.

The relationships between mechanical properties and microstructure of Ti-29Nb-13Ta-4.6Zr in under aged, peak aged and over aged conditions at various aging temperatures were investigated. The maximum Vickers hardness values of Ti-29Nb-13Ta-4.6Zr aged at 573 K, 673 K and 723 K are obtained at aging times of around 2419.2 ks, 3024 ks and 1209.6 ks, respectively. ω phase precipitates in β phase of Ti-29Nb-13Ta-4.6Zr at relatively low aging temperature, 573 K, while α phase precipitates in β phase of Ti-29Nb-13Ta-4.6Zr at relatively higher aging temperature, 723 K. At an aging temperature of 673 K that lies between aging temperatures of 573 K and 723 K, ω phase precipitates at the early stage of aging, but α phase precipitates at relatively longer aging time. The precipitation site of α phase changes from intragrain to grain boundary at around peak aging time when Ti-29Nb-13Ta-4.6Zr is aged at 673 K and 723 K. The tensile strength of Ti-29Nb-13Ta-4.6Zr aged at 573 K, 673 K and 723 K increases up to a peak aging time with increasing aging time, but under over aging conditions, the tensile strength decreases. While the elongation decreases with increasing aging time at every aging temperature. The fatigue strength of Ti-29Nb-13Ta-4.6Zr increases greater when α phase precipitates than when ω phase precipitates. The fatigue strength of Ti-29Nb-13Ta-4.6Zr decreases a little due to the coarsening of α phase precipitated in β grain.

Tensile and fatigue properties are important mechanical properties in drawn wires for biomedical and dental applications because of the credibility against the monotonic loading fracture or fatigue failure. The mechanical properties and deformation behavior of drawn wires of Ti-29Nb-13Ta-4.6Zr with diameters of 1.0 mm and 0.3 mm (designated as TNTZd1.0 and TNTZd0.3) were investigated to know a potential for biomedical and dental applications in this paper. The microstructure of forged Ti-29Nb-13Ta-4.6Zr subjected to a solution treatment at 1063 K (TNTZST) comprises a single β phase with an average diameter of 25 μm. While that of TNTZd1.0 comprises a needle-like single β phase elongated parallel to the drawing direction. Tensile strengths of TNTZd1.0 and TNTZd0.3 are approximately 740 MPa and 800 MPa, respectively. While both elongations are nearly equal to each other (approximately 5.0%). The elastic modulus of TNTZd1.0 is approximately 50 GPa and that slightly smaller than approximately 55 GPa of TNTZd0.3. The notch-fatigue limit of TNTZd1.0 is 250 MPa. TNTZST exhibits the maximum elastic strain of approximately 1.4%. And the stress-strain curve shows a single gradient during elastic deformation region. The stress-strain curves of TNTZd1.0 and TNTZd0.3 in the elastic deformation region show two gradients, and the values of the maximum elastic strains in both wires are approximately 2.9% and 2.8%, respectively.

Ti-29Nb-13Zr-2Cr, Ti-29Nb-15Zr-1.5Fe, Ti-29Nb-10Zr-0.5Si, Ti-29Nb-10Zr-0.5Cr-0.5Fe and Ti-29Nb-18Zr-2Cr-0.5Si were newly designed for dental applications. These alloys were designed based on Ti-29Nb-13Ta-4.6Zr (TNTZ), replacing relatively high melting point element, Ta, with beta stabilizing elements such as Cr, Fe and Si, which would lower the melting point of the alloy. Their melting points, mechanical properties, and cytotoxicity were investigated in this study. The following results were obtained. Melting points of designed alloys decrease about 50 to 370 K as compared with that of TNTZ, and Ti-29Nb-13Zr-2Cr has the lowest melting point around 2050 K. Vickers hardness of the surface of each designed alloy cast into modified magnesia based investment material is in the range of 400HV to 500HV, which is lower than that of TNTZ (around 560HV). Balances of the strength and the ductility of Ti-29Nb-13Zr-2Cr, Ti-29Nb-15Zr-1.5Fe and Ti-29Nb-10Zr-0.5Cr-0.5Fe are nearly equal to those of TNTZ. Cell viability of each designed alloy is excellent.

Essais de dissolution de Fe de purete commerciale, Fe−Si, Fe−Ni, Fe−Cu, Fe−Mn et Fe−C dans Al a 973, 1023 et 1073 K. Processus de dissolution differents suivant l'element allie au fer