Pseudo-texture memory in AISI 321 austenitic stainless steel

Abstract

In this study, a 45 µm-sized AISI 321 austenitic stainless steel was cryo-rolled at -196 °C to 50 % thickness reduction to completely transform the γ-austenite phase to α'-martensite. The cryo-rolled sample was subsequently annealed in the temperature range of 923 - 1073 K for 30-28800s (0.5 - 480 mins) to reverse the α'-martensite back to γ-austenite and develop ultrafine grain (UFG) structure at an optimum annealing condition. Average austenite grain sizes of 0.22 and 0.31 µm were obtained at an optimum annealing conditions of 923 K for less than 480 minutes and 1023 K for 10 minutes, respectively. High resolution EBSD and XRD texture results shows that ζ-fibre ({110}<uvw>) is the major texture component of austenite grains in the UFG structure and it is stronger in specimen annealed at 923 K than those of higher temperatures (973, 1023 and 1073 K) used in this study. The strong intensity of ζ-fibre in UFG is attributed to pseudo-texture memory in AISI 321 i.e. the ability of the steel to memorize the crystallographic orientation of the deformed austenite, rather than the conventional as-received austenite phase that is random.