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Strength and toughness of L1_0-type intermetallic TiAl with duplex structure.

双相结构L1_0型金属间化合物TiAl的强度和韧性

基本信息

批准号：
02650521
负责人：
SANO Takeshi
金额：
$ 1.22万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

Experimental studies were made on microstructure-controlled L1_0-TiAl mainly by means of transmission electron microscopy. Results are as follows.1. Microstructural variations of L1_0-ordered TiAl with Al contents.TiAl compounds ranged from 47 to 52 at% AI at intervals of 0.25 at% AI were solution heat treated at 1373 K. The structure was nearly single-phase gamma by optical microscope(OM)examination. During aging at 973 K, transmission electron mocroscope(TEM)revealed that no precipitates were found in the matrix gamma. TiAl compounds ranged from 56 to 62 at% Al at intervals of 2.0 at% AI were solution heat treated at 1473 K. The structure was the single-phase gamma by OM. TEM observation that TiAl_2 precipitate, which was not so fine, was formed during aging at temperatures in the range of 973 to 1173 K.2. Microstructural variations of stoichiometric L1_0-ordered TiAl containing 0.1 to 2.0 at% C or N.Fine needle-shaped Ti_3AlC and Ti_3AlN of perovskite type were formed only [001] direction of the L1_0 matrix during aging. The cross-section of the needle was not circular but square. In the carbon containing alloys, precipitates with the similar morphology and the same crystal structure was formed. The selected area electron diffraction analyses suggested that the precipitates had a perovskite-type crystal structure and had the orientation relationship(100)-Ti_3AlC/Ti_3AlN parallel to(100)TiAl and[001]-Ti_3AlC/Ti_3AlN parallel to [001]-TiAl. At higher temperatures, Ti_3AlC/Ti_3AlN precipitates were replaced by Ti_2AlC and Ti_2AlN with hexagonal lattice structure.3. Room temperature compression strength.The strength increase might be not so anticipatated by the precipitation of perovskite phase. The alloy containing 0.5 at% N indicated higher strength than that containing 0.5 at% C.

利用透射电子显微镜对L10-TiAl的显微组织控制进行了实验研究。研究结果如下：1.研究结果。TiAl化合物的显微组织随Al含量的变化而变化。TiAl化合物以0.25at%Al为间隔，在137K固溶处理，其组织为近乎单相的伽马相。在973K时效过程中，透射电子显微镜(TEM)显示，在基体中没有发现析出物。TiAl化合物以2.0at%Al间隔在56~62at%Al之间，在1473K进行固溶处理，OM分析其结构为单相的伽马相。透射电子显微镜观察到，在973~1173K的温度范围内，时效过程中形成了不太细小的TiAl_2析出物。化学计量比为0.1~2.0at%C或N的化学计量比TiAl的显微组织变化在时效过程中只在L10基体的[001]方向形成细小的针状钙钛矿型Ti3AlC和Ti3AlN。针的横截面不是圆形的，而是方形的。在含碳合金中，形成了具有相似形态和相同晶体结构的析出物。选区电子衍射分析表明，析出物具有钙钛矿型晶体结构，具有(100)-Ti3AlC/Ti3AlN平行于(100)TiAl和[001]-TiAlC/Ti3AlN平行于[001]-TiAl的取向关系。在较高温度下，Ti3AlC/Ti3AlN相被具有六方晶格结构的Ti2AlC和Ti2AlN所取代。室温压缩强度。钙钛矿相的析出可能没有预料到强度的增加。含0.5at%N的合金比含0.5at%C的合金具有更高的强度。