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

• 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

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

双相TiAl合金是一类具有巨大潜力的新型轻质高温结构材料，近五年来，它的研究取得了长足的进展。在此基础上，研制出了几种室温塑性可达3-4%、强度提高的双相工程双相TiAl合金。然而，层状结构仍然是差的延展性，虽然他们是有益的韧性和高温强度。因此，需要更多的工作来实现层状形式的强度和延展性的改善的平衡。据报道，一些合金元素如Cr、V和Mn可以提高双相形式的两相合金的室温延展性。然而，这些方法都不能有效地使两相合金以片层的形式延展。最近发现，两相TiAl合金的拉伸塑性和断裂应力对试验环境很敏感， ...更多信息 在真空或干燥空气中试验时，比在空气或氢气中试验时更好。拉伸延伸率和断裂应力对应变速率也很敏感，在空气或氢气中测试时，它们增加，而在真空中测试时，它们降低。这些结果清楚地表明，这类材料对环境脆化敏感。然而，近年来我们发现，添加合金元素可以降低环境对塑性的影响，因此，研究合金元素在两相TiAl合金，特别是层状TiAl合金的变形、断裂行为和环境脆化中的作用，对于开发具有良好力学性能的两相TiAl合金是必不可少的。在这个项目中，我们试图澄清铝含量的影响，然后添加过渡和非过渡元素的合金化，最后测试环境的变形和断裂行为的层状结构。在这些结果的基础上，我们试图指定的作用，一个特定的合金元素的变形和环境脆化行为的层状结构。这导致了为开发具有足够的强度、塑性和韧性的双相TiAl合金而建立的合金化策略，不仅室温下的塑性和韧性差，而且过高的制造成本一直阻碍着TiAl合金的结构应用。就制造成本而言，可铸造的TiAl合金是理想的。但是，铸态下不可避免的层状组织仍然是塑性和韧性差。本课题的研究结果对提高铸造TiAl合金层状组织的力学性能具有重要的指导意义，对铸造TiAl合金的发展具有重要的意义。少

项目成果

M.Yamaguchi and Y.Shirai: "Physical Metallurgy and Processing of Intermetallic Compounds" N.S.Stoloff and V.K.Sikka ed Chapman & Hall(in press),

M.Yamaguchi 和 Y.Shirai：“金属间化合物的物理冶金和加工” N.S.Stoloff 和 V.K.Sikka ed Chapman

H.Inui et al.: "Deformation of Ti-36.5 at % Al" Philosophical Magazine A. 69. 1161-1177 (1994)

H.Inui%20et%20al.:%20"变形%20of%20Ti-36.5%20at%20%%20Al"%20哲学%20杂志%20A.%2069.%201161-1177%20(1994)

K.Ito et al.: "Plastic deformation of CoSi2" Acta metall.mater.42. 1261-1271 (1994)

K.Ito 等人：“CoSi2 的塑性变形”Acta metal.mater.42。

Y.Shirai et al.: "Vacancies in A167Mn8Ti25" Intermetallics. 2. 221-224 (1994)

Y.Shirai 等人：“A167Mn8Ti25 中的空位”金属间化合物。

M.Yamaguchi et al.: "Environmental Embrittlement of PST TiAl" Trans.Mater.Res.Soc.Japan. 13B. 61-73 (1994)

M.Yamaguchi 等人：“PST TiAl 的环境脆化”Trans.Mater.Res.Soc.Japan。