ISOTHERMAL AGING BEHAVIOR OF Ti-29Nb-13Ta-4.6Zr NEW BETA ALLOY FOR MEDICAL IMPLANT

摘要

In this study, the isothermal aging behavior of the Ti-29Nb-13Ta-4.6Zr alloy quenched from 1033K was investigated employing electrical resistivity (ρ) and Vickers hardness (HV) measurement, optical microscopy (OM) and X-ray diffraction (XRD). On 573K aging, ρ at room and liquid nitrogen temperatures (RT and LN) increased up to 120ks and 30ks, respectively. Then, in both cases ρ decreased with continued aging. HV started to increase from 0.06ks and isothermal ω phase was identified at 300ks aging by XRD. On 623K aging, isothermal ω phase was also identified at 300ks by XRD whereas no α phase was identified during whole aging time. On 673K, aging precipitated α phase was identified at 300ks, whereas no reflections of isothermal ω phase appeared. Resistivity at RT and LN increased with the aging, similar to resistivity change of 573K aging. On 773K aging, an incubation period for ρ change at both temperatures of 6ks was observed, following which ρ decreased. An incubation period for HV change was extended up to 12ks and then HV increased. Precipitatedαwas observed and identified by OM and XRD, respectively, whereas no reflections of isothermal ω phase were identified during whole aging time at 773 K. The upper limit to temperature of isothermal ω precipitation is situated at around 673K.