Development of Microstructure-controlled L1_2-type High Temperature Intermetallics

主要采用透射电镜对γ′-Ni_3A1基金属间化合物的微观结构控制进行了实验研究。结果如下：Ll_2有序γ′-Ni_3 （Al, Ti）相中无序γ相的析出。在适当的温度范围内退火，可以得到含Ni过饱和的γ′-Ll_2有序相的均匀固溶体。变形诱导的Ll_2有序γ′-Ni_3 （Al, Ti）单晶微观结构中含有细小分散的无序γ析出相。超晶格位错在gma'相的均匀过饱和固溶体中解离成四重Schockley部分位错。含有无序γ沉淀的γ′-Ll_2有序相的硬化机制。从析出相中取出位错所需的额外功取决于基体和析出相之间反相边界能的差异。含无序γ析出的γ′-Ll_2有序Ni_3 （Al, Ti）单晶中较大的ld应力的温度依赖性在实验温度范围内，γ′-Ni_3 （Al, Ti）的强度随着γ粒子的析出而增加。含无序γ相的γ′-Ll_2有序Ni_3 （Al, Ti）单晶屈服应力的取向依赖性在（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。含无序γ相的高温变形Ni_3 （Al, Ti）单晶中的位错结构。超发散被无序粒子强烈吸引，并在基体的（111）平面上解离。ll_2有序Ni-Al-Cr合金中的析出。1423 K固溶处理后，在1073 K左右时效，位错上先出现细小的多面体相，然后在基体中析出。选择区电子衍射研究表明，这些颗粒为M_<23>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