Localized deformation bands in Portevin–LeChâtelier plastic instabilities at a constant stress rate

Portevin–Le Châtelier (PLC) plastic instabilities were examined in constant loading rate tensile tests. Irregular instability steps were observed in an intermediate stress rate region on the stress versus strain curves. The irregular steps are caused by the repeated activation of localized high deformation bands. The activation of the localized bands shows some regularity. The origin of the irregular instability steps goes back to the initialization of the first band at the onset point of the instabilities. It is argued that the appearance of irregular instability steps at low strain rates is related to the decrease of the depth of the dynamic strain aging toward small strains.