Abstract

The evolution of phase composition and hardness in the refractory titanium VT18U alloy (Ti–6.4Al–3.5Zr–2.6Sn–1Nb–0.6Mo–0.2Si) during aging for 1 h within a temperature range of 550–700°C has been studied by optical, scanning, and transmission electron microscopy; full-profile X-ray diffraction analysis; and durometry. An explanation is given to some specific features of changes in the crystal lattice constants (unit cell parameters) (β, α', α_II, α_I , and α₂) calculated by means of full-profile analysis for the phases formed under high-temperature treatment at 915°C and further aging in alloy VT18U. It has been shown that a maximum hardness at 650°C in aged alloy VT18U is correlated with a maximum amount of α₂-precipitates, which are formed at this temperature and detected by means of full-profile analysis. For an pilot VT18U-based alloy with an increased content of zirconium (7 wt %) and tin (4 wt %), some morphological features in the precipitation of α_II and α₂-phases have been established alongside with regularities of transformations due to doping with aluminum, zirconium, and tin in the phases (β, α_II, α_I, α₂) formed during aging at 700°C for 100 h.

中文翻译：

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难熔钛Ti-6.4Al-3.5Zr-2.6Sn-1Nb-0.6Mo-2Si合金时效时相组成和硬度特性的演变

摘要

难熔钛 VT18U 合金 (Ti-6.4Al-3.5Zr-2.6Sn-1Nb-0.6Mo-0.2Si) 在 550-700°C 温度范围内时效 1 h 过程中相组成和硬度的演变通过光学、扫描和透射电子显微镜研究；全剖面 X 射线衍射分析；和硬度计。解释了通过全剖面分析计算出的晶格常数（晶胞参数）（β、α'、α _II、α _I和α ₂ ）变化的一些具体特征。 - 915°C 温度处理，并在合金 VT18U 中进一步时效。已经表明，时效合金 VT18U 在 650°C 时的最大硬度与 α _{2的最大量相关。}-在此温度下形成并通过全剖面分析检测的沉淀物。对于锆 (7 wt%) 和锡 (4 wt%) 含量增加的试验性 VT18U 基合金，已经确定了 α _II和 α ₂相沉淀的一些形态特征以及由于转变的规律性在 700°C 老化 100 小时期间形成的相 (β, α _II , α _I , α ₂ ) 中掺杂铝、锆和锡。