The effect of twinning and slip on the Bauschinger effect of Hadfield steel single crystals

The Bauschinger effect (BE) in single crystals of Hadfield manganese steel (Fe, 12.3Mn, 1.0C in wt pet) was studied for three crystallographic orienta tions, [(1) over bar 11], [(1) over bar 23], and [001]. Both forward tensio n-reverse compression (FT/RC) and forward compression-reverse tension (FC/R T) loading schemes were used to investigate the role of deformation history on the BE. The evolution of stress-strain response and a dimensionless Bau schinger parameter were used to study the BE. The BE stems from long-range back stress generated by the dislocation pileups at the twin and localized slip boundaries. Twinning boundaries present a strong obstacle and lead to a strong BE. If localized slip followed twinning, permanent softening was e vident, such as in the case of the [111] FT/RC scheme. Localized slip and m ultiple slip in the forward loading provided a transient effect in the stre ss-strain response without a significant permanent softening. Hadfield stee l single crystals have demonstrated a high BE for orientations conducive to combined twinning/slip deformation. The BE increased with increasing prest rain, then saturated and started to decrease, in contrast with precipitatio n-hardened alloys. A unique strain-hardening approach along with the back s tress calculation was introduced into a viscoplastic self-consistent (VPSC) formulation. The strain-hardening formulation incorporates length scales a ssociated with spacing between twin lamellae. The simulations correctly pre dicted the BE and the stress-strain response for both forward and reverse l oading.