材料期刊网

An amorphous-like phase, the mixture of amorphous phase and microcrystalline beta-Ni(Al,Ti) compound, has been synthesized by mechanically alloying the Ni50Al25Ti25 elemental powder mixtures in a high energy ball mill. It has been found that titanium plays a dominant role in this process. There exist two types of transformations of amorphous-like Ni50Al25Ti25 upon heating: first, the amorphous-like alloy transforms into a disordered Ni2AlTi compound (b.c.c. structure) at 345-445 degrees C, and then into an ordered Ni2AlTi compound at 554-626 degrees C. Tt is suggested that at the low-temperature transition, the Ni atoms locate in the corners of the b.c.c. lattice, but the cubic centers are occupied randomly by Al and Ti atoms. When the temperature rises to 554 degrees C, a long-range ordering transition occurs, resulting in the formation of ordered Ni2AlTi. The ordering energy of Ni2AlTi has been measured as 4.35 kJ mol(-1).