Mechanical Synthesis and Heat Treatment of Ni75Ti25 Alloy

The investigations of the microstructure changes of Ni75Ti25 powder prepared by mechanical alloying in as-milled state and after annealing treatment were performed. The X-ray diffraction (XRD) method was used to investigate a mechanically induced solid state reaction between nickel and titanium powders. The crystallite sizes and lattice strains were analyzed by using Williamson-Hall method. The compacted powder morphology was analyzed by SEM method. The Ni(Ti) solid solution was formed as a result of the milling process. The crystallite sizes of all alloys are below 100 urn. The annealing treatment, in the temperature range of 773 K to 1173 K leads to reduction of the breadth of Ni(Ti) diffraction lines, which indicates the increasing of the crystallites' size. However, the phase composition of annealed Ni75Ti25 powder does not change, so the presence of any Ni-Ti intermetallic phases is not stated.