| The effects of powder process on combustion characteristics, microstructure and mechanical properties of the Ni₃Al compounds were studied. Ni₃Al-B allays fabricated by the combustion synthesis with the reactive sintering(RS) and self-propagating high-temperature synthesis(SHS) showed a relative density of 97% and 96%, respectively. The microstructure of the alloys by both processes consisted of equiaxed grains of 30㎛ in size and uniformly distributed pores. Proper consolidation of the alloys required an optimum range of the green density, 65∼70% of theoretical. Excessive addition of ZrO₂also impaired the sintered density and hindered complete alloying. While the particle size ratio(d_(Al)/d(Ni)) was important in combustion synthesis, the heating rate was particularly critical in reactive sintering. Ni₃Al-B-ZrO₂alloy processed by RS showed a combination of tensile yield strength, 500MPa and tensile ductility, 10%, whereas that by SHS had inferior mechanical properties due to segregation of ZrO₂particles. |
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