Advanced Steel Metallurgy: Characterization
Program Organizers: Chirag Mahimkar, Big River Steel; Justin Raines, SSAB Americas; Kip Findley, Colorado School of Mines; Alla Sergueeva, NanoSteel Company Inc; Daniel Branagan, The NanoSteel Co

Wednesday 8:00 AM
November 4, 2020
Room: Virtual Meeting Room 39
Location: MS&T Virtual


8:00 AM  
Microstructure Characterization and Post-heat Treatment Design for High-Strength Low-alloy Steels Strengthened with Fe2SiTi-L21 Precipitates: Rafael Rodriguez De Vecchis1; Soumya Sridar1; Xin Wang1; Zhangwei Wang2; Wei Xiong1; 1University of Pittsburgh; 2Max-Planck-Institut für Eisenforschung GmbH
    Copper-bearing high-strength low-alloys (HSLA) steels are suitable candidate materials for naval applications as they exhibit high strength and toughness as well as good weldability. In an effort to further increase their strength, precipitation hardening with intermetallic phases is reported to be promising. Though the strengthening effect of Cu and M2C precipitates in HSLA steels are well studied, the effect of Fe2SiTi-L21 precipitates remains unexplored. Hence, in this work, two different compositions close to HSLA-100 steel are designed using a CALPHAD-based ICME (CALPHAD: Calculations of Phase Diagrams; ICME: Integrated Computational Materials Engineering) framework with Fe2SiTi as the major secondary phase. The evolution of phase change and precipitation kinetics were systematically studied via the CALPHAD-approach and experiments. The latter confirms the principal role of co-precipitation of Cu and Fe2SiTi nano-sized precipitates at boosting the hardness from 428 HV in as-cast condition up to 717 HV after optimum heat treatment.

8:20 AM  
Microstructure Property Relationships of Al- alloyed Medium Manganese Steels: Alexandros Serafeim1; Christian Haase1; Wolfgang Bleck1; 1Steel Institute (IEHK)
    The demand for reduction of automotive CO2 emissions has led to the development of the 3rd generation advanced high strength steels. One of the most promising candidates in that generation are Medium Manganese Steels (MMnS). In order to improve robustness of these materials for industrial processing, the addition of Al and Si is being considered. In this study, three MMnS with varying Al contents have been investigated. The kinetics of austenite reversion and microstructural changes, such as dislocation density and recrystallization, were investigated using XRD, SEM and EBSD. A correlation of the microstructure with the respective properties was performed with respect to deformation and damage accumulation in different phases. It was found that there are four different deformation behaviors, which are controlled by the interaction between austenite stability and the ratio of Mn/Al as well as the annealing temperature and time.

8:40 AM  
Relationship between Microstructure and Tensile Properties on High Strength Medium Carbon Mo-Nb-B Microalloyed Q/Q&T Steels: Irati Zurutuza1; Nerea Isasti1; Eric Detemple2; Volker Schwinn2; Hardy Mohrbacher3; Pello Uranga1; 1CEIT and TECNUN (University of Navarra); 2AG der Dillinger Hüttenwerke; 3NiobelCon bvba
    Advanced thermomechanical hot rolling schedules followed by direct quenching are being applied in industry for the production of quenched and tempered plates, in order to avoid an additional reheating and quenching treatment after hot rolling. With the purpose of exploring the synergetic effect of microalloying elements such as Nb, Mo or Nb-Mo with B, laboratory thermomechanical simulations were performed using plane strain compression; consisting of an initial preconditioning step, followed by several roughing and finishing deformation passes and a final accelerated cooling step. After quenching, a conventional tempering treatment was applied. The relationship between austenite and final martensite after quenching was evaluated using the EBSD technique and the effect of tempering was also explored in terms of microstructure and tensile properties. The aim of the current manuscript is to find the correlation between quenched martensite, quenched and tempered structure and the resulting tensile properties.

9:00 AM  
Study of the Effect of Accumulative Angular Drawing Process Conditions on Grain Refinement in Selected Stainless Steel Grade: Maciej Szymula1; Krzysztof Muszka1; Janusz Majta1; Marek Packo1; Jerzy Dybich2; 1AGH University of Science and Technology; 2BHH MIKROHUTA SP. Z O.O.
     Stainless steel grades (both austenitic and ferritic) find a wide application in critical applications due to their superior properties such high strength, excellent corrosion resistance, good biocompatibility. Manufacturing e.g. medical equipment and implants made of stainless steel grades often involves wire drawing operations. Further improvement of mechanical properties require further research in the field of grain refinement which is the main strengthening mechanisms that does not decrease the ductility and toughness. In the present work, capabilities of grain refinement in austenitic steel grade using recently developed technology of Accumulative Angular Drawing (AAD) [1-2] is studied. Focus is put on analysis of the influence of process parameters on inhomogeneity of microstructure and related mechanical properties. The effects of complex deformation modes and strong strain accumulation are studied in the light of possible grain refinement through Scanning Electron Microscope (SEM), Electron Backscatter Diffraction (EBSD) and mechanical testing tools. [1] M. Wielgus, J. Majta, J. Luksza, M. Packo, Effect of strain path on mechanical properties of wire drawing products, Steel Research International, Vol. 81 no. 9 spec. ed., 490-493 (2010)[2] K. Muszka, L. Madej, J. Majta, The effect of deformation and microstructure inhomogenities in the Angular Accumulative Drawing (AAD), Materials Science and Engineering A, 574, 68-74 (2013)