Mechanism of intense shear failure in Ni3Al single crystals

摘要

Localized shear bands, with minute misorientations off the slip plane, cause sharp failures in Ni3Al single crystals that fail after elongation exceeding 70-80% in room-temperature tensile tests. An explanation for intense slip plane shear failure, consistent with prior experimental observations, is proposed. Prior electron microscopy evidence obtained by Horton, Baker and Yoo of decreasing antiphase-boundary energy in highly deformed slip bands is employed to suggest a highly localized order-disorder transition. This shear-strain-induced slip-plane disordering provides the essential mechanism to lower the work-hardening rate to zero or negative values. A decreasing work-hardening rate sustains persistent shear localization, ultimately leading to failure. This mechanism is suggested to be applicable to other ordered crystals.