Predicting the effect of strain path on the strain aging behaviour of Ultra-low carbon steel

TL;DR

This study adapts a model to predict how strain path changes influence strain aging and bake hardening in ultra-low carbon steel, revealing effects on yield strength and work hardening rate.

Contribution

It introduces an adapted model that predicts strain path effects on strain aging behavior in ULC steel, considering dislocation and solute interactions.

Findings

Aging increases yield strength and alters work hardening rate.

Yield strength increase linked to reduced mobile dislocation density.

Work hardening behavior depends on dislocation roles post-aging.

Abstract

A recently presented model is adapted to predict the effects of strain path change on the strain aging (bake hardening) behaviour of an ultra low carbon (ULC) steel. Samples pre-deformed by rolling were aged and then tested in uniaxial tension at 0, 45 and 90$^\circ$ degrees to the prior rolling direction. The results show that aging changes not only the yield strength of the material but also the work hardening rate. The increase in yield strength is interpreted to be dominated by a reduction in mobile dislocation density, this reflecting the classic ideas of Hahn and others. The change in work hardening behaviour is treated as arising from the different role played by solute `loaded' dislocations compared to dislocations generated by straining after aging.