Development of Microstructure-controlled L1_2-type High Temperature Intermetallics

本文主要用透射电镜对γ ′-Ni_3Al基金属间化合物的显微组织控制进行了实验研究。研究结果如下：1.无序γ相在Ll_2有序γ ′-Ni_3（Al，Ti）相中的沉淀。在合适的温度范围内退火，可以得到均匀的γ '-Ll_2有序相固溶体，Ni过饱和.含有弥散分布γ相的Ll_2有序γ ′-Ni_3（Al，Ti）单晶的形变诱导显微组织超晶格位错在gma'相的均匀过饱和固溶体中解离为四重Schockley部分位错.γ ′-Ll_2有序相中含有无序γ相的硬化机制从沉淀物中拉出位错所需的额外功取决于基体和沉淀物之间的反相边界能的差异。yie的温度依赖性 关于我们 γ ′-Ll_2有序Ni_3（Al，Ti）单晶中γ相无序析出的ld应力。γ ′-Ni_3（Al，Ti）合金的强度在实验温度范围内是由于细小γ粒子的析出而提高的.γ ′-Ll_2有序Ni_3（Al，Ti）单晶中γ相的屈服应力与晶向的关系在（111）滑移发生的温度范围内，（111）[101]滑移的临界分解剪应力随温度的升高而减小.含γ相的Ni_3（Al，Ti）单晶高温形变位错结构超位错被无序粒子强烈吸引，并在（111）面上解离. Ll_2有序Ni-Al-Cr合金中的沉淀在1423 K固溶处理后，在1073 K附近时效，细小的多面体沉淀物首先出现在位错上，然后出现在基体中。选区电子衍射研究表明，这些颗粒是<23>M_C_6型碳化物。少

Experimental studies were made on the microstructure control of gamma'-Ni_3A1 based intermetallics mainly by means of transmission electron microscopy. Results are as follows.1. Precipitation of disordered gamma phase in an Ll_2 ordered gamma'-Ni_3 (Al, Ti) phase. A uniform solid solution of gamma'-Ll_2 ordered phase supersaturated with Ni can be obtained annealing in a suitable temperature range.2. Deformation induced microstructure of Ll_2 ordered gamma'-Ni_3 (Al, Ti) single crystals containing fine dispersion of disordered gamma precipitates. Superlattice dislocations dissociate into fourfold Schockley partial dislocations in a uniform supersaturatred solid solution of the gma' phase.3. Hardening mechanisms in a gamma'-Ll_2 ordered phase containing disordered gamma precipitates. Extra work necessary to pull out the dislocations from the precipitate is dependent on the difference in antiphase boundary energy between the matrix and the precipitates.4. Temperature dependence of the yie … More ld stress in gamma'-Ll_2 ordered Ni_3 (Al, Ti) single crystals containing disordered gamma precipitates. The strength of gamma'-Ni_3 (Al, Ti) increases over the temperature range of experiment by the precipitation of fine gamma particles.5. Orientation dependence of the yield stress in gamma'-Ll_2 ordered Ni_3 (Al, Ti) single crystals containing disordered gamma precipitates. The critical resolved shear stress for (111) [101] slip decreases with increasing temperature in the temperature range where (111) slip operates.6. Dislocation structures in high temperature deformed Ni_3 (Al, Ti) single crystals containing disordered gamma precipitates. The super dislovations are strongly attracted to the disordered particles and dissociate on the (111) plane in the matrix.7. Precipitation in Ll_2-Ordered Ni-Al-Cr alloys. By aging at temperatures around 1073 K after solution treatment at 1423 K, fine polyhedral precipitates appear firstly on the dislocations and then in the matrix. The selected area electron diffraction studies revealed that these particles are a M_<23>C_6 type carbide. Less