Nanocrystalline Ni_3Al alloy produced by mechanical alloying of nickel aluminides and hot-pressing consolidation

摘要

The reduction of grain size to the nanometer scale can improve the mechanical properties of materials, including intermetallic compounds. In the present study, the mechanical alloying process followed by hot-pressing consolidation has been used to obtain nanocrystalline Ni_3 Al intermetallic compound. Nanocrystalline powders of Ni(Al) supersaturated solid solution containing 25 at. % of Al were prepared by ball milling of AlNi or Al_3 Ni_2 alloys with addition of Ni powder. Subsequently, the milling products were sintered at 1000℃ under a pressure of 7.7 GPa. The XRD investigations of the consolidated pellets revealed that: (Ⅰ) ordering of Ni(Al) solid solution and its transformation into a Ni3 Al intermetallic compound occurs during sintering and (Ⅱ) the material remained nanocrystalline after sintering. The microhardness of Ni_3Al intermetallic produced in this work is of about 980 HV 0.1, the density of compacted materials is nearly 100% of theoretical value and their open porosity is negligible.