Role of Effective Strain During Cold Rolling Deformation on Mechanical Characteristics of AISI 304 Steel

Abstract

The plastic cold rolling deformation is one method to enhance the microstructure and mechanical characteristics of austenitic steel. The role of effective strain $\left( \varepsilon \right)$ during cold rolling deformation of the AISI 304 austenitic stainless steel has been studied. The results of the research were collected based on the means of optical, field emission-scanning electron microscopy, X-ray diffraction, microhardness, and tensile stress–strain tests. After 80% of ε, the size of coarse grains of the austenitic phase $(\gamma_{FCC} )$ was diminished as well as larger domains were generated from the martensitic phase $\left( {\alpha^{\prime}_{BCC} } \right)$. Also, the large carbide particles (M₂₃C₆) have been fragmented and they were sprinkled in both phases during the cold rolling process. Therefore, the dislocation density (ρ) has augmented for the deformed alloys. Consequently, the hardness and the ultimate strength (UTS) values are improved to ≈ 150% and ≈ 200%, respectively with increasing the effective strain to 80%. Generally, the increase of the effective strain leads to diminished grain size and increased the values of hardness, yield stress (YS) and UTS of the samples, meanwhile it causes the decrease of their ductility. Moreover, the values of YS have been calculated based on Hall–Petch, Orowan equations and dislocation strengthening formula. Finally, the calculated and the measured results were compared, where both of them are very matching especially at lower values of effective strain.

Graphic Abstract

SEM micrographs of AISI 304 steel samples (a) So, (b) S2, (c) S4 and (d) S5 that were subjected to different percent of plastic deformation during the cold rolling process.