CHEMICALLY DISORDERED NI3AL SYNTHESIZED BY HIGH-VACUUM EVAPORATION

Films of chemically disordered fcc Ni3Al were synthesized by the vacuum evaporation of Ni3Al onto room temperature and liquid nitrogen temperature substrates. X-ray diffractometry and transmission electron microscopy showed the material to be single phase with an average grain size of about 4 nm. The formation of the equilibrium L1(2) ordered phase occurred simultaneously with grain growth at temperatures above 350-degrees-C. Differential scanning calorimetry provided ordering enthalpies of 7 kJ/mole and 9 kJ/mole for material evaporated onto room temperature and liquid nitrogen temperature substrates, respectively.