MECHANICAL ALLOYING AND CHARACTERIZATION OF NI50AL25TI25

An amorphous-like phase, the mixture of amorphous phase and microcryst alline beta-Ni(Al,Ti) compound, has been synthesized by mechanically a lloying the Ni50Al25Ti25 elemental powder mixtures in a high energy ba ll mill. It has been found that titanium plays a dominant role in this process. There exist two types of transformations of amorphous-like N i50Al25Ti25 upon heating: first, the amorphous-like alloy transforms i nto a disordered Ni2AlTi compound (b.c.c. structure) at 345-445 degree s C, and then into an ordered Ni2AlTi compound at 554-626 degrees C. T t is suggested that at the low-temperature transition, the Ni atoms lo cate in the corners of the b.c.c. lattice, but the cubic centers are o ccupied 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).