Effects of Aging on Phase Constitution, Lattice Parameter and Mechanical Properties of Ti-4 mol%Au Near-Eutectoid Alloy

Abstract

Effects of aging on phase constitution, lattice parameters and mechanical properties of Ti-4 mol%Au near-eutectoid alloy were investigated. The alloy was fabricated by Ar arc-melting method, followed by homogenization at 1273 K for 3.6 ks. The ingot was cold-rolled with 95% reduction in thickness, solution treated at 1173 K for 0.9 ks and quenched into ice water. It was found that the apparent phase after the solution treatment was a supersaturated solid solution of (hcp) phase. This supersaturated -phase is termed m , hereafter. The apparent phase of the aged alloys was m regardless of the aging temperature from 373 to 1073 K for 3.6 ks. The 0.2% flow stress was decreased as the aging temperature increased. On the other hand, by the isothermal aging at 973 K, Ti 3 Au with A15 structure was formed and the volume fraction of Ti 3 Au increased with increasing aging time. The 0.2% flow stress of the materials was decreased as the volume fraction of Ti 3 Au increased. This indicates that the Ti 3 Au precipitations are not effective on strengthening of the Ti-Au alloy.

Defect-rich decorated TiO2nanowires for super-efficient photoelectrochemical water splitting driven by visible light

“…39 In the present study, the growth temperature (675-750 1C) for the nanowires is lower than the lowest eutectic temperature in the bulk Au-Ti binary system (832 1C). 40 It should be noted that the actual eutectic temperature of a nanoscale material is expected to be lower than that of the bulk under the same pressure conditions. 41 We therefore expect that the growth of these nanowires occurs by both vapour-solid and VLS mechanisms as the catalyst state changes from a solid state to a liquid state throughout the temperature range.…”

A Review of Investigations on Microstructure and Mechanical Properties of the Present Achievements of the Ti-Au-based Shape Memory Alloys

“…Matsuki et al found that the rapid-quenched Ti-4Au alloy performed high stability in terms of thermal property, where the performances, such as mechanical properties, were barely affected when the alloys were subject to various annealing-treatments. 22) Moreover, it was further found that after various annealing-treatments were conducted on the Ti-4Au alloys, the aforementioned undesired Ti 3 Au (crystal structure of A15) was not generated through the eutectoid phase transformation of β → α + A15. Both the abovementioned high thermal stability and phase constituent free from Ti 3 Au compound indicate that the Ti-4Au alloy could be a promising material for the practical uses.…”

“…Besides to the thermal stability and phase constituent issues, the workability of the materials, which is also a crucial prerequisite for practical uses, is also necessary to be considered. It was discovered that, opposite to the Zr-4Au alloys possessing poor workability, the Ti-4Au alloys performed excellent workability, 22,23) which is beneficial for the synthesis of the biomedical materials with certain dimensions and shapes.…”

“…Nevertheless, it was found that the near-eutectoid Ti-Au alloy (i.e., Ti-4Au) underwent the massive transformation during the rapid quenching process resulting in a massive martensite phase (α m ), which is not propitious for SMAs due to a lacking of functional properties of this α m phase, such as SME and SE behavior. 22,[24][25][26] Besides, it was found that the high transformation temperature of the Ti-4Au alloy makes it not practicable. 22) It is, therefore, necessary to tailor the Ti-4Au alloy by adding a third element to impose the functionalities and also to reduce the martensitic transformation start temperature (M s ) for the biomedical applications in the human body.…”

“…22,[24][25][26] Besides, it was found that the high transformation temperature of the Ti-4Au alloy makes it not practicable. 22) It is, therefore, necessary to tailor the Ti-4Au alloy by adding a third element to impose the functionalities and also to reduce the martensitic transformation start temperature (M s ) for the biomedical applications in the human body. 27,28)…”