The presence of calcium phosphate invert glass-ceramic (designated as CPIG) layer on the surface of artificial implant products can improve the bonding between these products and bones. In this study, the morphology of the CPIG layer on the surface of a -type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), was investigated for biomaterial applications by a dip-coating treatment. Furthermore, the mechanical properties of TNTZ coated with the CPIG layer were also investigated.In the CPIG layer, a compositionally gradient zone with a thickness of approximately 2.0 mm exists on the surface of the TNTZ. The titanium concentration in the zone increases with the decreasing distance from the CPIG surface toward the base materials. On the other hand, calcium and phosphorus concentrations in the zone increase with the distance from the TNTZ surface. The tensile bonding strength between TNTZ and the CPIG layer is 25 MPa and that between aged TNTZ and the CPIG layer is 18.6 MPa.For easily understanding the change in mechanical properties by a dip-coating treatment, the values of those on TNTZ and TNTZ coated with CPIG layer were shown as follows. The tensile strength increases remarkably by a dip-coating treatment as compared with that of assolutionized TNTZ while the elongation is a reverse trend. Young's modulus of TNTZ and aged TNTZ coated with the CPIG increases by 15 to 27 GPa after the dip-coating treatment as compared with that of as-solutionized TNTZ (approximately 60 GPa). The fatigue limit of TNTZ coated with the CPIG layer is nearly equal to that (approximately 300 MPa) of as-solutionized TNTZ. On the other hand, the fatigue limit of aged TNTZ coated with the CPIG layer is a 100 MPa higher than that of as-solutionized TNTZ.

No abstract

No abstract

Ni-Cr binary alloys containing high amount of Cr demonstrate gamma/alpha-Cr lamellar structure by discontinuous precipitation (DP) reaction from grain boundary. The mechanism of DP reaction is caused by supersaturated Cr in the gamma phase. Supersaturated Cr concentration influences the driving force for the DP reaction and the lamellar spacing. Moreover, the Ni-based alloys with high Cr, containing Al, significantly increase the hardness and strength due to the very narrow lamellar structure. Al addition brings on Ni consumption in the matrix by precipitation of the gamma prime phase. Therefore, Cr supersaturates dramatically in the matrix. The wrought Ni-Cr-Al alloy, Ni-38Cr-3.8Al (mass%) , reaches extremely high tensile strength, which is over 2 GPa, after annealing treatment. Even though chemical composition of Ni-38Cr-3.8Al is simple, the microstructure is complex because it consists of the gamma/alpha Cr lamellar structure with the fine gamma prime particles. Therefore, in this study, we investigated the influence of Cr concentration on the cellular precipitation behaviour. In order to understand the influence of Cr concentration, Ni-34, 36 and 38Cr-3.8Al alloys were prepared. Forged bars were subjected to solution treatment in the gamma single phase region. Subsequently, the alloys were aged from 873K to 1073 K for various times. The cellular precipitation reaction is suppressed by a decrease in Cr concentration, particularly at low temperature annealing treatment condition. The hardness is low in lower Cr concentration alloys in all range of annealing treatment temperature. These results indicate that Cr concentration remarkably affects the driving force for the DP reaction.

No abstract