Abstract
NiAl intermetallic compound, B2 type nickel-aluminide, is of particular interest because it combines good oxidation-resistance with a high melting point. In this study, NiAl alloys were produced by the mechanical alloying (MA) process for the purpose of refine-ment of microstructures. The MA was carried out in the attritor mill using pure nickel powder(4-7μm in diameter) and alloy powder (Ni-62.5at%Al, 43μm in average diameter) as starting materials. Mechanically alloyed powders were consolidated by the hot pressing. Changes of microstructures and mechanical properties during MA were investigated. MA proc-essing for longer periods produced the grain refinement and led to the formation of α-Al2O3 and Ni3Al phase in the NiAI matrix due to the oxidation of aluminum during MA. In the bending test for NiAl specimens produced under the condition of optimum MA processing time, the large deflection was obviously obtained above about 673K. Observing fracture surfaces, it was also found that the transition from a brittle cleavage fracture mode to a ductile fracture mode was caused by the application of the MA process even at the room temperature . These results are suggesting that MA process has good effect on the improvement of the ductility for NiAl.
