Formability prediction of interstitial-free steel via miniaturized tensile specimen for Rapid Alloy Prototyping

This study aims to investigate the feasibility of using non-standard miniaturized tensile specimens (MTS) to characterize the formability features of interstitial-free (IF) steel, specifically DX57 steel. The motivation behind this research is to gain insight into the accuracy of predicted values for the steel's formability using the designed non-standard MTS, which could potentially be used to test materials obtained from rapid alloy prototyping (RAP) routines. Tensile tests were conducted using both standard bars and non-standard MTS with different angles to the rolling directions (0 ??, 45 ??, and 90 ??) and the experiment results were used to determine the material properties for the following numerical simulations, which were based on the cross-die deep drawing concept. The results show that the non-standard MTS over-predicted the strain hardening exponent compared to the values obtained from the standard tensile bars. For the same punch stroke, the non-standard miniatured tensile specimen under-predicted the punch force. However, for the deformed blank, the thickness variation along different paths was compared, and the maximum thickness value difference was found to be less than 5%. In terms of the forming limit diagram (FLD), the MTS's prediction is very close to the standard test-piece's prediction; the overall major-minor strain status of the deformed blank is similar. The results of this research provide confidence in the ability to evaluate formability from small-scale tensile tests for heterogeneous alloys such as synthetic IF steels developed during RAP.