Exploring forming limit of stainless steel below room temperature by Nakazima tests using an actively cooled additively manufactured punch

The hardening behavior of metastable austenitic stainless steel 1.4301, which undergoes the Transformation Induced Plasticity (TRIP) effect, is influenced by various factors, including the plastic strain, the temperature, and the current martensite content. Investigating the forming limit of this material in relation to temperature is, therefore, crucial to understand its processability and determining its range of applications. Since the forming limit curve (FLC) above room temperature has been extensively studied for this stainless steel, this paper aims to provide a comprehensive theoretical-experimental investigation of the FLC slightly below room temperature. To that end, a cooled punch was designed, and the experimental setup was defined to perform isothermal Nakazima experiments at and temperatures. The modified maximum force criterion (MMFC) was applied to the experiments to predict the theoretical FLC of the stainless steel. Non-isothermal Nakazima tests were used to validate the MMFC calibration. The cooled punch with confocal cooling channels performed isothermal Nakazima tests within . The forming limit of was below the one of and the MMFC could predict the FLC and the non-isothermal paths within an overall accuracy deviation of . Through the present investigation, we found that the martensite transformation occurs too fast at to prolong the forming potential. • Experimental setup for forming limit curve by subcooled temperatures • Reduced forming potential of stainless steel at compared to • Modified Maximum Force Criterion predicts isothermal as well as non-isothermal forming limits very well.