Effects of ternary elements and environment on mechanical properties of TiAl intermetallics

三元元素和环境对TiAl金属间化合物力学性能的影响

基本信息

批准号：
06044259
负责人：
YAMAGUCHI Masaharu
金额：
--
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Overseas Scientific Survey.
财政年份：
1994
资助国家：
日本
起止时间：
1994 至无数据
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06044259/
关键词：
TiAl Mechanical Properties Ductility Alloying Alloying Elements Environment

项目摘要

Extensive progress and improvements in two-phase TiAl alloys, which have great potential as a new class of light-weight high-temperature structural materials, have been made in the last about five years. Based on these achievements, several engineering two-phase TiAl alloys in duplex form with room-temperature ductility up to 3-4% and improved strength have been developed. However, the lamellar structures are still poor in ductility, although they are beneficial for toughness and high-temperature strength. More work is thus needed to achieve an improved balance of strength and ductility in the lamellar form. Some alloying elements such as Cr, V and Mn have been reported to increase the room-temperature ductility of the two-phase alloys in duplex form. However, none of them is effective in ductilizing the two-phase alloys in lamellar form.Recently, tensile ductility and therefore fracture stress of two-phase TiAl alloys have been found to be sensitive to test environment ; they are high … More er when tested in vacuum or in dry air than in air or in hydrogen gas. The tensile elongation and fracture stress are also sensitive to strain rate ; they increase when tested in air or in hydrogen gas while they decrease when tested in vacuum with increasing strain rate. These results clearly suggest that this class of materials is susceptible to environmental embrittlement. However, we have recently found that the environmental loss in ductility may be reduced by alloying additions.Thus, it is indispensable to clarify the role of alloying elements in the deformation and fracture behavior and the environmental embrittlement of the two-hhase TiAl alloys, in particular those in lamellar form for the development of two-phase TiAl alloys with wellbalanced mechanical properties. In this project, we attempt to clarify the effects of aluminum content and then alloying additions of transition and non-transition elements and finally test environment on the deformation and fracture behavior of the lamellar structure. On the basis of these results, we try to specify the role of a particular alloying element in the deformation and environmental embrittlement behavior of the lamellar structure. This leads to the establishment of alloying strategy for the development of two-phase TiAl alloys with enough strength, ductility and toughness for their structural applications.Not only poor ductility and toughness at room temperature but also excessive fabrication cost have been hindering the structural application of TiAl alloys. Castable TiAl alloys is desirable in respect of fabrication cost. However, the lamellar structure inevitable under as-cast conditions is still poor in the ductility and toughness. We expect that results of this project will have a great significance in alloying strategy to improve the mechanical properties of the lamellar structure and thereby put a considerable impact on the development of castable TiAl alloys. Less

两相TiAl合金作为一类新型轻质高温结构材料具有巨大的潜力，在过去大约五年的基础上，基于这些成就，一些工程两相TiAl合金取得了广泛的进展和改进。已经开发出室温延展性高达 3-4% 且强度有所提高的双相合金，但是，尽管片状结构有利于韧性和高温强度，但延展性仍然较差。因此，需要努力实现层状形式的强度和延展性的改善平衡，据报道，一些合金元素（例如 Cr、V 和 Mn）可以提高双相合金的室温延展性。它们都不能有效地使两相合金以层状形式延展。最近，人们发现两相 TiAl 合金的拉伸延展性和断裂应力对测试环境很敏感；在真空或干燥空气中测试时比在空气或氢气中测试时拉伸伸长率和断裂应力也对应变率敏感；在空气或氢气中测试时拉伸伸长率和断裂应力增加，而在真空中测试时则降低。这些结果清楚地表明这类材料容易受到环境脆化的影响，但是，我们最近发现合金添加剂可以减少环境造成的延展性损失。因此，阐明合金化的作用是必不可少的。元素对两相 TiAl 合金（特别是层状形式）的变形和断裂行为以及环境脆性的影响，以开发具有良好平衡机械性能的两相 TiAl 合金。在本项目中，我们试图阐明其影响。铝含量，然后合金化添加过渡和非过渡元素，最后测试环境对层状结构的变形和断裂行为的影响。在这些结果的基础上，我们尝试指定特定的作用。合金元素在层状结构的变形和环境脆化行为中的作用，这导致了合金化策略的建立，以开发具有足够结构应用的强度、延展性和韧性的两相TiAl合金。室温和过高的制造成本一直阻碍着 TiAl 合金的结构应用，但在制造成本方面，可铸 TiAl 合金是不可避免的。我们预计该项目的结果对于改善层状结构的力学性能的合金化策略具有重要意义，从而对可铸TiAl合金的发展产生重大影响。