Development of Heat Resistant Ni_3Al Base Cermet Using Mechanical Alloying Process.

以纯Ni、纯Al和纯TiC粉末为原料，采用机械合金化-热压法制备了TiC颗粒含量为20、40、60、80vol%的Ni_3Al （Ni-24.5 mol%Al-0.3mol%B）基复合合金和TiC颗粒含量为0vol%的Ni_3Al （Ni-24.5 mol%Al-0.3mol%B）基复合合金。对机械合金化过程中粉末形貌变化等现象进行了详细研究。研究了烧结试样的显微组织、力学性能和氧化性能。采用机械合金化法制备了直径小于10mm的细粉末颗粒。烧结后的复合合金由Ni_3Al基体、少量Ni固溶体和均匀分散的TiC颗粒组成。尽管0vol% ~ 40vol%的TiC合金在任何温度下都能观察到塑性应变，但60vol%和80vol%的TiC合金仅在高于673K和1073K的温度下才发生塑性变形。当TiC含量为0vol% ~ 40vol%时，合金的流动应力在400K ~ 700K时呈现平台区，然后显著减小。结果表明，该基基合金的应变速率敏感指数（m值）大于0.4，表明合金发生了超塑性变形。而TiC颗粒复合合金的m值小于0.3。在1273K氧化试验中，质量增益随着TiC体积分数的增加而增加。基体合金的氧化膜厚度很薄，仅由Al_2O_3组成，而含TiC合金的氧化膜厚度则由Al_2O_3和TiO_2组成。

Ni_3Al (Ni-24.5 mol%Al-0.3mol%B) matrix composite alloys with 20,40,60 and 80vol%TiC particles and a matrix alloy with 0vol%TiC were produced by mechanical alloying - hot press process using pure Ni, pure Al and TiC powders. Details of phenomenon like morphological change of powders during mechanical alloying process were studied. Also, the microstructures and the mechanical properties as well as the oxidation properties of sintered specimens were investigated. Fine powder particles with diameter of less than 10mum were produced by mechanical alloying. Sintered composite alloys were found that they consist of Ni_3Al matrix with small amount of Ni solid solution and uniformly dispersed TiC particles. Although the plastic strain was observed for the 0vol% - 40vol%TiC alloys at any temperature investigated, 60vol% and 80vol%TiC alloys deformed plastically only at higher temperatures than 673K and 1073K,respectively. The flow stresses for alloys with 0vol% - 40vol%TiC exhibited the plateau region from 400K to 700K,and then decreased markedly. It was revealed that the strain rate sensitivity exponent (m value) for the base matrix alloy was over 0.4, indicating the development of superplastic deformation. On the other hand, the composite alloys with TiC particles showed lower m values than 0.3. Mass gain during oxidation test at 1273K increased with TiC volume fraction. While the thickness of the scale observed for the matrix alloy was very thin and composed of only Al_2O_3, TiC containing alloy formed the thick scale consisting of both Al_2O_3 and TiO_2.