Nonequilibrium Phase Transformations in Titanium Aluminides with Ternary Additions

三元添加物铝化钛的非平衡相变

• 批准号: 9616748
• 负责人: James Wittig
• 金额: $ 24.06万
• 依托单位: Vanderbilt University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-06-01 至 2001-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9616748&HistoricalAwards=false
• 关键词: Nonequilibrium; Phase; Transformations; Titanium; Aluminides

9616748 Wittig This research examines the massive phase transformations in binary and ternary Ti-Al alloys to determine the parent to product crystallographic relationships and the effects of ternary elements on the nucleation and growth of the massive transformation product. The base alloy has a composition of Ti-48at%Al. To this stoichiometry, additions of the ternary elements V, Nb, Cr, Mo, Mn, and Fe are added. Initially the work concentrates on the V, Cr, and Mn series from row four of the periodic table. By utilizing the University of Vanderbilt's undercooling, rapid quench technology, unique nonequilibrium microstructures are formed that should help clarify present confusion regarding the site preferences of ternary additions to gamma TiAl. The rapidly cooled, splat- quenched samples are analyzed using optical microscopy, X- ray diffraction, scanning electron microscopy and analytical electron microscopy. By employing ALCHEMI to compare the non-equilibrium microstructures of undercooled and rapidly quenched TiAl ternary alloys with equilibrium conditions, the site occupation of the ternary elements can be characterized as a function of Ti/Al stoichiometry. %%% Knowledge of the influence of ternary atom additions on the unit cell structure is critical to the understanding of the atomic mechanisms responsible for improved mechanical properties observed in the Ti-Al 48at% ternary alloys. The high cooling rate, solid-state transformations explored in this research give some insights onto other nonequilibrium processes such as those found in the heat-affected zones of welded alloys. ***

小行星9616748 本研究探讨了二元和三元Ti-Al合金中的块状相变，以确定母体与产物的晶体学关系以及三元元素对块状相变产物的成核和生长的影响。 该基础合金具有Ti-48at%Al的组成。对于该化学计量，添加三元元素V、Nb、Cr、Mo、Mn和Fe。 最初的工作集中在V，Cr和Mn系列从周期表的第四行。 通过利用范德比尔特大学的过冷，快速淬火技术，形成独特的非平衡微观结构，应有助于澄清目前的混乱，关于三元添加到γ TiAl的网站偏好。 利用光学显微镜、X射线衍射、扫描电子显微镜和分析电子显微镜对快速冷却、溅射淬火的样品进行了分析。 采用ALCHEMI比较过冷和快淬TiAl三元合金的非平衡态组织与平衡态组织，三元元素的占位可以表征为Ti/Al化学计量比的函数。 三元原子添加对晶胞结构的影响的知识是至关重要的原子机制的理解，负责改善Ti-Al 48at%三元合金中观察到的机械性能。 在这项研究中探索的高冷却速率，固态转变给其他非平衡过程，如那些发现在焊接合金的热影响区的一些见解。 ***