Development of Light Weight-High Temperature Structural L1_2 Compounds in Al_3Ti-Base Alloys.

Al_3Ti基合金中轻质高温结构L1_2化合物的开发。

• 批准号: 07650822
• 负责人: MABUCHI Hiroshi
• 金额: $ 1.41万
• 依托单位: Osaka Prefecture University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07650822/
• 关键词: Light weight heat-resistant material; Titanium trialuminide; Intermetallic compound; Crystal structure control; Equilibrium phase diagram; Ductility improvement; Oxidation resistance; 延性・脆性改善

The intermetallic compound Al_3Ti is very attractive as a potential high-temperature structural material. Some of the positive characteristics of this compound are its good oxidation resistance, low density of 3.3 g cm^<-3>, and relatively high melting point of about 1673 K.However, it has the low-symmetry tetragonal D0_<22> structure and is brittle at room temperature. Successful development of this aluminide depends on whether we can overcome its brittleness at ambient temperature. One possible approach to ductilize ordered intermetallics with low-symmetry crystal structures is to change their structures to those of higher symmetry. Indeed, it is known that replacing a certain amount of aluminum atoms in Al_3Ti with Zn, Ni, Cu, or Fe changes the structure of Al_3Ti(D0_<22>) to the L1_2 structure. The authors found the formation of new ternary L1_2 compounds in Al_3Ti-base alloys containing Mn, Cr, Ag, Rh, Pt, and Au. Many studies on the Al-Ti-X (X=Ni, Fe, Cu, Mn, Cr, Ag and Pd etc.) … More alloys have focused on the mechanical properties of the ternary L1_2 trialuminide compounds. However, the ternary L1_2 compounds are still brittle in tension and/or bending, although they exhibit appreciable compressive ductility at ambient temperature.Recently, much work has been made of the microstructure, especially second phases and porosity generally induced by a homogenization treatment, and microstructure-mechanical property relationships of the ternary L1_2 trialuminide compounds. The present authors more recently reported also the effects of manganese on the microstructure and mechanical properties of ternary L1_2 intermetallic compounds in the Al_3Ti-based alloys, and that the titanium trialuminide containing Mn does posses some bend ductility at room temperature when porosity is reduced.In the present study, sintering of elemental powders was carried out to form ternary L1_2 intermetallic compounds in Al-Ti-Cr alloys. The L1_2 phase field and equilibrium phases surrounding the L1_2 phase at 1423K have been established. Besides the L1_2 phase, the pertinent second phase fields have been also estimated ; TiAl, TiAl_2, Ti_2Al_5, Al_3Ti, Al_<17>Cr_9, AlCr_2, and TiAlCr phase fields. The vertical section of the Al-25mol%Ti-Cr alloys has been experimentally determined, and the presence of the L1_2+ Liquid phase field in the present composition and temperature ranges was confirmed. Button ingots of some ternary L1_2 compounds in the Al-Ti-Cr alloys were prepared by arc-melting to investigate their microstructure (especially second phases and porosity), microhardness, and bend ductility. In general, homogenization of as arc-melted alloys substantially reduced the amount of second phases but introduced extensive porosity. Therefore, the formation of porosity is closely associated with second phase solutionized during homogenization treatment. However, no residual porosity was observed in higher Cr content alloys. The porosity after homogenization was observed when Al_<17>Cr_9 phase is formed and not when TiAlCr or AlCr_2 phase is formed. The ternary L1_2 compounds in the Al-Ti-Cr alloys had some bend ductility at ambient temperature, which can be increased to about 0.9% (plastic bend strain) by increasing the Cr content when porosity is reduced. Less

金属间化合物Al_3Ti是一种极具潜力的高温结构材料。该化合物具有良好的抗氧化性、低密度（3.3 g cm^<-3>）和较高的熔点（约1673 K）。但它具有低对称的四方D0_<22>结构，在室温下脆性较大。这种铝化物的成功开发取决于能否克服其在常温下的脆性。利用低对称结构的有序金属间化合物延展性的一种可能方法是将其结构改变为高对称结构。事实上，我们知道用Zn、Ni、Cu或Fe取代Al_3Ti中一定量的铝原子会使Al_3Ti（d0 <22>）的结构变为l12结构。作者发现在含有Mn、Cr、Ag、Rh、Pt和Au的al_3ti基合金中形成了新的三元l12_2化合物。对Al-Ti-X （X=Ni, Fe, Cu, Mn, Cr, Ag， Pd等）合金的力学性能研究较多，主要集中在三元L1_2三铝化物化合物的力学性能上。然而，三元l12化合物在拉伸和/或弯曲时仍然是脆的，尽管它们在室温下表现出可观的压缩延展性。近年来，人们对l12 -三铝化物三元化合物的微观结构，特别是均匀化处理引起的第二相和孔隙率以及微观组织与力学性能的关系进行了大量的研究。本文作者最近还报道了锰对al_3ti基合金中三元l12_2金属间化合物的微观组织和力学性能的影响，以及含锰的三铝化钛在降低孔隙率时具有一定的室温弯曲延展性。本研究采用元素粉末烧结的方法，在Al-Ti-Cr合金中制备了三元l12金属间化合物。在1423K时建立了l_2相场和l_2相周围的平衡相。除l_2相外，还估计了相应的第二相场；TiAl、TiAl_2、Ti_2Al_5、Al_3Ti、Al_<17>、Cr_9、AlCr_2和TiAlCr相场。对Al-25mol%Ti-Cr合金的纵截面进行了实验测定，证实了l12_2 +液相场在现有成分和温度范围内的存在。采用电弧熔炼法制备了Al-Ti-Cr合金中l12_2三元化合物的扣锭，研究了其显微组织（特别是第二相和孔隙率）、显微硬度和弯曲延展性。一般来说，电弧熔化合金的均匀化大大减少了第二相的数量，但引入了广泛的孔隙。因此，孔隙的形成与均匀化处理过程中第二相的固溶密切相关。而在Cr含量较高的合金中，没有观察到残余孔隙。均匀化后的孔隙是在形成Al_<17>的Cr_9相时出现的，而不是在形成TiAlCr或AlCr_2相时。Al-Ti-Cr合金中的三元l12_2化合物在室温下具有一定的弯曲塑性，当孔隙率降低时，增加Cr含量可使合金的塑性弯曲应变提高到0.9%左右。少

项目成果

H.Mabuchi: "Combustion Synthesis of TiAl-matrix Composites in the Ti-Al-BN System." Scripta Metall.Mater.32. 253-257 (1995)

H.Mabuchi：“Ti-Al-BN 系统中 TiAl 基复合材料的燃烧合成”。

H.Mabuchi: "Combustion Synthesis of TiAl-matrix Composites in the Ti-Al-BN System." Scripta Metall.Mater.32-2. 253-257 (1995)

H.Mabuchi：“Ti-Al-BN 系统中 TiAl 基复合材料的燃烧合成”。

間渕 博: "燃焼反応プロセスにより作製したTiAl-Ti_2AlC複合材料の組織と機械的性質" 紛体および粉末冶金. 42-11. 1289-1294 (1995)

Hiroshi Mabuchi：“燃烧反应工艺制备的TiAl-Ti_2AlC复合材料的结构和机械性能”粉末与粉末冶金42-11（1995）。

H.Mabuchi: "Compositional Effects on Formation and Properties of Ternary L1_2 Compounds on Al_3Ti." Proc.3rd Japan Inter.SAMPE Symp. 3-2. 1530-1535 (1993)

H.Mabuchi：“Al_3Ti 上三元 L1_2 化合物的形成和性能的成分影响”。

H. Mabuchi: "Effects of Manganese on the Ll_2 Compound Formation in Al_3Ti-base Alloys." Intermetallics. 4-S. S193-S199 (1996)

H. Mabuchi：“锰对 Al_3Ti 基合金中 Ll_2 化合物形成的影响”。