Cg. Kallingal et al., FATIGUE DAMAGE ACCUMULATION IN NI3AL AND NIAL, Materials science & engineering. A, Structural materials: properties, microstructure and processing, 193, 1995, pp. 502-510
The accumulation of fatigue damage during strain-controlled cycling (l
ow-cycle fatigue) of single crystals of NiAl and very coarse-grained p
olycrystals of Ni3Al+W in air at room temperature is described. Surfac
e topography was studied for all test materials by scanning electron m
icroscopy and, in the case of Ni3Al+W polycrystals, also by profilomet
ry. The development of persistent slip bands and an extrusion-intrusio
n morphology were recorded, as were transmission electron microscopy o
bservations of dislocation substructures. Point-defect clusters, dipol
es and other evidence of damage due to cycling were noted in both inte
rmetallics. The density of dipoles was non-uniform and was modulated o
n the slip plane in NiAl, unlike Ni3Al+W, which displayed a homogeneou
s distribution. Computer simulation of the microstructure in NiAl has
been carried out, based upon the mechanism of dipole diffusion in a st
ress gradient.