Nanocrystalline matrix Al3Ni2-Al-Al3Ni composites produced by reactive hot-pressing of milled powders

Mechanically alloyed nanocrystalline Al63Ni37 powder with a metastable structure of NiAl intermetallic phase was mixed with 30 vol.% of Al powder. This powder mixture was consolidated under the pressure of 7.7 GPa at 600, 700, 800 and 1000 °C for 15 and 180 s. During the consolidation, in all cases, the metastable NiAl phase transformed into the equilibrium Al3Ni2 intermetallic. Moreover, a solid-state reaction between the intermetallic matrix and Al occurred, yielding an Al3Ni phase. Progress of this reaction depended on the consolidation temperature and temperature exposure time, thus Al3Ni2-Al, Al3Ni2-Al-Al3Ni or Al3Ni2-Al3Ni composites were produced by hot-pressing with various parameters. The mean crystallite size of the Al3Ni2 intermetallic matrix in the composites is 39-67 nm, depending on consolidation parameters. The composites hardness is in the range of 6.02-7.51 GPa.