M. Dao et al., MECHANISM OF INTENSE SHEAR FAILURE IN NI3AL SINGLE-CRYSTALS, Philosophical magazine. A. Physics of condensed matter. Structure, defects and mechanical properties, 75(2), 1997, pp. 443-459
Localized shear bands, with minute misorientations off the slip plane,
cause sharp failures in Ni3Al single crystals that fail after elongat
ion exceeding 70-80% in room-temperature tensile tests. An explanation
for intense slip plane shear failure, consistent with prior experimen
tal observations, is proposed. Prior electron microscopy evidence obta
ined by Horton, Baker and Yoo of decreasing antiphase-boundary energy
in highly deformed slip bands is employed to suggest a highly localize
d order-disorder transition. This shear-strain-induced slip-plane diso
rdering provides the essential mechanism to lower the work-hardening r
ate to zero or negative values. A decreasing work-hardening rate susta
ins persistent shear localization, ultimately leading to failure. This
mechanism is suggested to be applicable to other ordered crystals.