Flow localization and shear band formation in a precipitation strengthened austenitic stainless steel

Flow localization and shear band formation in a γ′ strengthened austenitic stainless steel, JBK-75, was investigated by means of compression of reduced-gage-section, cylindrical specimens. The specimens were deformed in a strain rate range of 10³ to l0³s^-1 and from 650 °C to 1100 °C. The alloy exhibited an extreme susceptibility for macroscopic localized flow when the microstructure contained fine γ′ precipitates on the order of 10 nm. At high strain rates localized flow in the precipitate containing structures took the form of macroscopic, transgranular shear bands. At low strain rates the localized flow occurred mainly in precipitate-free zones along high angle grain boundaries. Localized flow was always associated with the occurrence of dynamic recrystallization. Other mechanisms for flow localization, including the effects of adiabatic heating on γ′ precipitate dissolution, are discussed.