Understanding the Deformation Mechanisms in Austenitic Iron-Manganese Steels with Changes in Stacking Fault Energy, Strain Rate and Tempeature

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TECHNICAL SUMMARYTo understand the complex deformation mechanisms exhibited by austenitic iron-manganese steels, which include transformation-induced plasticity (TRIP), twinning-induced plasticity (TWIP), and dislocation glide, requires systematic mechanical testing with materials characterization down to the atomic scale. Changes in stacking-fault energy (SFE) with composition and temperature strongly influence the active deformation mechanism. Although the determination of SFE is challenging and most investigations rely on calculated values, careful experimental methods using weak-beam dark field (WBDF) imaging of partial dislocation separation can provide accurate SFE measurements. In addition to the composition and deformation temperature, important microstructural and processing parameters include grain size and strain rate. Correlation of the SFE with the mechanical behavior is a critical aspect for developing a basic understanding of the structure-property-processing relationships that will allow for future advances in the design of new high-manganese austenitic steels.NON-TECHNICAL SUMMARYIn the last five years, there has been a significant increase in the research activity associated with high-manganese austenitic steels as evidenced by both the number of scientific publications and patent applications. These steels are excellent candidates for applications requiring high formability and energy absorption such as cold-stamping of automotive parts owing to their exceptional ductility, strain-hardening, and toughness. This proposal describes collaboration between Vanderbilt University, the Ohio State University, the RWTH University and the Max-Planck-Institut für Eisenforschung in Germany, and the Oak Ridge National Laboratory to address the basic science involved with the future development of high-manganese austenitic steels. This international collaboration not only allows the combined expertise of the individual investigators to be focused on understanding the complex deformation mechanisms in these alloys, but it will also promote the education of graduate students who will benefit from the international experience. Student education and training will be enhanced through international collaborations. Educational opportunities enabled by these activities will be made available to under-represented groups through the Vanderbilt-Fisk Bridge program.