Mechanical Synthesis and Heat Treatment of Ni75Ti25 Alloy
The investigations of the microstructure changes of Ni75Ti25powder 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 nm. 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 at the increase in size of crystallites. However, the phase composition of annealed Ti75Ni25powder does not change, so the presence of any Ni-Ti intermetallic phases is not stated.