Alloy Design Based on Computational Thermodynamics and Multi-objective Optimization: The Case of Medium-Mn Steels
- PDF / 6,354,737 Bytes
- 19 Pages / 593.972 x 792 pts Page_size
- 91 Downloads / 165 Views
TION
MEDIUM-MN Steels containing 2 to 10 wt pct Mn, have received considerable attention as potential candidates for the third generation of advanced highstrength steels for use primarily in light-weight automotive applications. These steels aim to fill the gap between high-manganese twinning-induced plasticity steels and low-alloy transformation-induced plasticity steels. They were first introduced by Miller,[1] who focused his experiments on a 0.11C-5.7Mn steel with ultrafine-grained microstructure. Excellent combinations of strength and elongation could be achieved by retained austenite stabilization through the partitioning of C and Mn by suitable thermomechanical treatment in the intercritical range. Since then, significant progress has been made as many researchers aim to further improve properties and processability in medium-Mn compositions. Although many and sometimes complex heat treatments have been proposed, the most widely used method of producing chemically and mechanically stabilized austenite is through intercritical annealing of either hot-rolled or cold-rolled material. Relevant publications are summarized in Table I, which depicts the alloy composition, annealing conditions, fraction of retained austenite, and associated mechanical properties.
JOHN S. ARISTEIDAKIS and GREGORY N.HAIDEMENOPOULOS are with the Laboratory of Materials, Department of Mechanical Engineering, University of Thessaly, Pedion Areos, 38500 Volos, Greece. Contact e-mail: [email protected] Manuscript submitted October 7, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
The Mn content in this list varies between 3 and 11 wt pct while some recent studies have focused on the importance of Al, in concentrations up to 4 wt pct, as an effective way to increase annealing temperatures, inhibit cementite precipitation, and improve the overall retained austenite characteristics.[2] Recent advances in medium-Mn steels have been lately discussed.[12] The large variation in the Mn content and intercritical annealing conditions indicates that the development of this new class of steels is mostly based on empirical approaches. There have been limited attempts to systematically investigate the Fe-C-Mn-Ni-Al composition space and identify the effect of alloying elements and annealing conditions on the development of microstructure and associated mechanical properties. These limited efforts include the application of CALPHAD-based approaches to determine the effect of alloy composition[13] and the solute partitioning during intercritical annealing,[14] to select the optimum annealing temperature for a specific medium-Mn composition[3] and the tensile behavior during deformation of medium-Mn steels.[4] Kang et al.[13] studied computationally the effect of alloying on the equilibrium behavior of retained austenite in a Fe-C-Mn system, with the addition of Si, Al, or Cr. A similar model that also considers the effect of the austenite grain size and the martensitic transformation kinetics was employed by Lee and De Cooman,[3] in order to select a suitable ann
Data Loading...
