Effect of Aging Treatment on Microstructure and Mechanical Properties of a Two-phase Titanium Alloy

摘要

Abstract: In present work, microstructure of Ti-6Al-2Mo-l.5Cr-2Sn-2Zr-lV-0.15Si-0.4Fe alloy as a function of aging temperature was investigated using optical microscopy, scanning electron microscopy (SEM), x-ray diffraction (XRD) and transmission electron microscopy (TEM).Three types of precipitates were found in this alloy, they were α_2 phase (Ti_3Al), silicides, and Sn rich phase. Ti_3Al were observed in all aged specimens covering a range 500-740°C. A method of quantitative analysis toward α_2 based on high resolution images and Flourier transformation is used. The results showed that the ordering in a phase was highly related to the property of fracture toughness. Silicides were first found at 580°C ageing and later determined in the formulate (Ti_(5+x)Zr_(3-x))Si_3 in the specimens aged at 740°C, and they were found to influent the fracture toughness significantly. The Sn rich phase was emerged with large area during the 780°C aging. And its direct correlation to property was not found. The density of acicular a phase was found almost invariable by calculating through the modification XRD quantitative analysis during the elevated aging temperature.