The synthesis and characterization of ultrafine grain NiAl intermetallic

The nanocrystalline NiAl powders were synthesized by mechanical alloying (MA), and the ultrafine grain NiAl bulk materials were subsequently consolidated by vacuum hot-pressed sintering. The microstructure and mechanical properties of milled powders and bulk materials were characterized. The results reveal that the NiAl powders were synthesized after 1.67 h of milling and the grains of NiAl were refined to 18 nm after 22 h of milling. During milling, the temperature rise caused by MA led to the annealing effect and consequently resulted in the abnormal decrease in microstrain and microhardness. NiAl bulk material with a relative density of 99.4% was prepared after sintering at 1300 °C and its grain size was about 400 nm. Due to fine-grain strengthening, the compressive stress and compressive strain of NiAl bulk material were significantly improved at room temperature.