Hardening Behavior and Model of a 316L Sheet Considering Macro and Micro Size Effects

Abstract

316L stainless steel is often used as the metal bipolar plate, which is a key component of fuel cells. For the thinner metal bipolar plates, the mechanical properties may be different for different specimen sizes. In this paper, the mechanical properties, metallographic structure, and hardening behavior of 316L stainless steel sheets with different grain sizes and specimen thickness were studied. Several mathematical models were selected to describe the hardening behavior of 316L stainless steel sheet. A correlated hardening model of 316L stainless steel was established, considering the specimen and grain size effect. The results show that the specimen thickness has no effect on the microstructure and grain size, but the austenite grain size increases gradually with an increase in holding time. With a decrease in plate thickness and an increase in grain size, the strength decreases. Compared to the 0.1 mm sheet, the yield strength and tensile strength for the 0.9 mm sheet are increased by 48% and 24%, respectively. The yield strength and tensile strength are decreased by nearly half after 20 min heat treatment due to the grain size growth. The thicker the sample and higher the grain size is, the higher the hardening rate is. The predicted stress–strain by established correlated hardening model has a good agreement with the experiment curves.