Microstructure, phase composition and hardness evolution in 316L stainless steel processed by high-pressure torsion

Authors: Gubicza, J., El-Tahawy, M., Huang, Y., Choi, H., Choe, H., Lábár, J.L. and Langdon, T.G.

Journal: Materials Science and Engineering: A

Volume: 657

Pages: 215-223

ISSN: 0921-5093

DOI: 10.1016/j.msea.2016.01.057

Abstract:

A 316L stainless steel was processed by high-pressure torsion (HPT) to evaluate the grain refinement and phase transformation. The initial material was essentially a single phase γ-austenite with a coarse-grained microstructure of ~42μm but the grain size was reduced to ~45nm after 10 turns of HPT. In addition, there was a phase transformation and the initial γ-austenite transformed initially to ε-martensite and finally to α'-martensite with increasing strain. The dislocation density increased to an exceptionally high value, of the order of ~1016m-2, in the main α'-martensite phase after 10 HPT revolutions. The formation of the multiphase nanocrystalline microstructure yielded a four-fold increase in hardness to reach an ultimate value of ~6000MPa. The Hall-Petch behaviour of the HPT-processed alloy is compared directly with coarse-grained materials.

Source: Scopus