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Mechanical Properties of Ordered and Disordered Ni3Al Films 2/2/01 3:18 PM page 1 Comparison of Mechanical Properties of Ni3Al Thin Films
 

Summary: Mechanical Properties of Ordered and Disordered Ni3Al Films 2/2/01 3:18 PM page 1
Comparison of Mechanical Properties of Ni3Al Thin Films
in Disordered FCC and Ordered L12 Phases
Y. HUANG, M. J. AZIZ, J. W. HUTCHINSON, and A.G. EVANS*
Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
R. SAHA, W. D. NIX
Dept. of Materials Science and Engineering, Stanford University, Stanford, CA 24305
ABSTRACT
We 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

  

Source: Aziz, Michael J.- School of Engineering and Applied Sciences, Harvard University

 

Collections: Physics; Materials Science