Effect of Prior Austenite Grain Size on the Annealing Twin Density and Hardness in Austenitic Stainless Steel

The present study examined the effect of prior austenite grain size on twin density and hardness of austenitic stainless steels (ASS). The 253 MA and 316L ASS were subjected to multipasscold rolling to reduce thickness up to 2.3 mm. Subsequently, the rolled steels were heat treatedat 1100°C at 0, 900, 1800, 2700, and 3600 seconds in a tubular furnace in a hydrogen atmosphere.At the end of the annealing time, the rolled steel was quenched in the cooled zone of the tubularfurnace until it reached room temperature in a hydrogen atmosphere. Then, microstructureobservation of ASS was done to identify the austenitic grain size and annealing twin, and a hardnesstest was performed using the micro-Vickers hardness scale. The line intercept method was used tomeasure the changes in 253 MA and 316L austenitic grain sizes. ImageJ software was used tomeasure grain size and twin length. The results showed that austenite grains of both steels grewnormally; 253 MA ASS had a lower SFE and K value than 316L ASS, which indicated that 253 MAASS had sluggish grain growth, smaller grains, more easily formed annealing twins, and higher twindensity. The Hall–Petch coefficient, K’, of 253 MA ASS was higher than 316L ASS, which resulted ina higher hardness value. The Sellars, Pande and Hall-Petch models were shown to predict austenitegrain sizes, twin density, and hardness in 253 MA and 316L ASS