Huang, YucongAziz, MichaelHutchinson, JohnEvans, Anthony G.Saha, R.Nix, Wiliam D.2009-04-202001Huang, Yucong, Michael J. Aziz, John W. Hutchinson, Anthony G. Evans, R. Saha, and William D. Nix. 2001. Comparison of Mechanical Properties of Ni[sub]3Al Thin Films in Disordered FCC and Ordered L1[sub]2 Phases. Acta materialia 49(14): 2853-2861.1359-6454http://nrs.harvard.edu/urn-3:HUL.InstRepos:2797290We report the results of several experiments isolating the effect of long-range order on mechanical properties of intermetallic compounds. Kinetically disordered FCC Ni₃Al (Ni 76%) thin films were produced by rapid solidification following pulsed laser melting. For comparison, compositionally and microstructurally identical films with ordered L1₂ structure were produced by subsequent annealing at 550 °C for 2 hours. These FCC and L1₂ Ni₃Al thin films were tested by nanoindentation for hardness and Young’s modulus, and the critical strain to fracture was measured by straining the substrate under four-point bending. Ni₃Al thin films in the disordered phase were found to have nearly twice the critical strain to fracture, more than three times the fracture toughness, and about 20% lower hardness than in the ordered counterpart. Blunter crack tips and crack bridging observed in the disordered phase also illustrate increased ductility. The increased plasticity of Ni₃Al due to chemical disorder is manifested both within the grains and at the grain boundaries. Young’s moduli of the ordered and disordered materials were found to be indistinguishable.en-USorder-disorder phenomenahardness testingintermetallic compoundstoughnessrapid solidification10.1016/S1359-6454(01)00094-5