The effectiveness of the cryogenic rolling vis-à-vis room temperature rolling on strengthening was significantly affected by stacking-fault energy and there was an optimum stacking-fault energy at which cryogenic rolling was most effective. Studies on Al, Al alloy AA6061, Cu, Cu–4.6Al, Cu–9Al and Cu–15at% Al alloys revealed that in metals with very high and very low stacking-fault energies, the strength difference between cryogenic and room-temperature rolled samples was <10%. The Cu–4.6Al alloy with an intermediate stacking-fault energy revealed maximum enhancement of strength (25–30%). These results were explained by changes in deformation mechanisms with stacking-fault energy and temperature. High stacking-fault energy metals deformed by dislocation slip and low stacking-fault energy metals deformed by twinning during cryogenic and room-temperature rolling. Metals with intermediate stacking-fault energies deformed by twinning during cryogenic rolling but by dislocation slip during room-temperature rolling, and this made cryogenic rolling most effective over room-temperature rolling in enhancing the strength.

Role of Stacking Fault Energy in Strengthening Due to Cryo-Deformation of FCC Metals. V.S.Sarma, J.Wang, W.W.Jian, A.Kauffmann, H.Conrad, J.Freudenberger, Y.T.Zhu: Materials Science and Engineering A, 2010, 527[29-30], 7624-30