Anisotropic strain hardening following load reversal during high-temperature creep testing of superalloy single crystals

A critical examination and qualitative evaluation of anisotropic creep behavior in nickel-based superalloy CMSX-4 single crystals is provided with respect to previously established models describing pure shear creep of specimens deformed at high temperatures. Using double-shear creep deformation samples, a complete reversal of applied creep stress results in a large increase in creep rate in the opposite direction. During forward creep, dislocation networks build up that are trapped in γ channels along γ/γ′ interfaces. The sense reversal in applied stress effectively releases the dislocation networks, resulting in a large jump in measured creep rates.