Interactions of Phase Transformations and Plasticity: Session 8
Program Organizers: Valery Levitas, Iowa State University

Thursday 4:00 PM
July 13, 2017
Room: Water Tower
Location: Hyatt Regency Chicago

Session Chair: Lars Bumke, University of Kiel

4:00 PM  
Studies of the Extruded Ni-Co-Mn-In Metamagnetic Shape Memory Alloys: Krystian Prusik1; Edyta Matyja1; Maciej Zubko1; Marian Kubisztal1; 1University of Silesia
    Magnetic shape memory alloys exhibit reversible martensitic transformation which may be driven by temperature, external strain or magnetic field resulting in macroscopic shape change. Magnetic force induced strain (MFIS) and high frequency response make this materials promising magnetic actuators. In single crystalline Ni–Mn–Ga alloys MFIS may even reach over 10% of longitudinal strain. In the polycrystalline alloys due to the statistical orientation of the grains MFIS is practically not observed. In other to improve the orientation of the grains the directional solidification, high temperature plastic deformation and extrusion may be applied. In this studies the effect of high temperature extrusion process on the structure and properties of the Ni-Co-Mn-In alloys were analyzed. The structure of the alloys were studied by SEM, XRD and the (HR)TEM. Texture measurements were performed by the HKL EBSD. Magnetic measurements were done by VSM (PPMS7).

4:20 PM  
Residual Stress and Texture Evolution on Surface of 304L TRIP Steel Sheet Subjected to FLC Test: Isabela Santana de Oliveira1; Juciane Maria Alves2; Ramon Botelho2; Andersan dos Santos Paula2; Luiz Paulo Brandão2; Marcelo Costa Cardoso3; Luciano Pessanha Moreira1; Maria Carolina dos Santos Freitas1; 1Universidade Federal Fluminense; 2Instituto Militar de Engenharia; 3Universidade Federal do Rio de Janeiro
    The martensite formation in the outer and inner blank sheet surfaces of the metastable 304L austenitic steel subjected to the Forming Limit Curve (FLC) testing, performed according to the Marciniak method, was analyzed in regions located near and away from the failure site. Magnetic measurements and X-ray diffraction (XRD) techniques were used to evaluate the strain-induced martensite phase transformation. XRD was also used for the quantification of texture. The mechanical properties were measured by Vickers Instrumented Ultramicrohardness. From the results were observed some aspects as greater diversity in the martensite formation and austenite hardening on outer sheet surface. The mechanical properties showed distinct behavior depending on the martensitic fraction and on biaxial expansion deformation mode conjugated to higher hardening associated with the deformation texture.

4:40 PM  
An investigation on the microstructure and mechanical properties of hot rolled medium manganese TRIP steel: Yu Zhang1; Hua Ding1; 1Northeastern University
    Microstructure and mechanical properties of hot rolled medium manganese TRIP steel were investigated in present study. The heat treatment schedule was intercritically annealing at various temperature (640℃, 665℃ and 690℃) for 1 hour and water quenched. The results showed that an excellent combination of high strength and adequate ductility was obtained. As the intercritical annealing temperature increased, the ultimate tensile strength and strain hardening rate increased, while the total elongation increased firstly and then decreased. A large amount of austenite could be retained at room temperature by adopting the method of intercritically annealing. Austenite stability and initial microstructure before deformation played an important role in the mechanical properties and strain hardening rate.

4:55 PM  
A Thermomechanical Approach of Modeling Martensitic Transformation Using Crystal Plasticity Theory: Rashid Khan1; Amir Siddiq2; Umair Asim2; Adel Abdelghaffar1; Nashmi Alrasheedi1; 1Al Imam University; 2University of Aberdeen
     The current work is related to the development of constitutive model that capture the overall behavior of austenite based steel, which undergoes martensitic transformation when subjected to thermomechanical load. In the present model, transformation and twinning induced plasticity are incorporated together using crystal plasticity theory. Initially, kinematics of deformation mechanism is developed by defining elastic, plastic, and transformation deformation gradients. Secondly, an energy balanced principle is used to develop a novel thermodynamic framework where dissipated energy, Helmholtz free energy, and driving potential equations are formed. Then, numerical integration scheme is developed and implemented in ABAQUS as a user-defined material subroutine. Furthermore, three dimensional finite element models of single and polycrystal austenite are developed. Finite element model is validated through experimental results and found to be in good agreement. Finally, further simulations are performed to predict the behavior of austenite based steels subjected to different loading conditions.

5:15 PM  
Dynamic Transformation Characteristics of 22MnB5: Mei Zhang1; Yi YAO1; Xiaohang ZHOU1; 1Shanghai University
    Based on Gleeble-3500 and DIL805 dilatometer, dynamic and static continuous cooling transformation behavior and CCT curves of commercial steel 22MnB5 were tested and compared with each other. The increasing deformation amount (from 0 to 40%) increases the starting of the austenite to ferrite transformation temperature (Ar1) considerably, from 1000K (727℃) to 1065K (792℃). Dynamic continuous cooling conditions obviously extend the ferrite phase field and narrow the bainite phase field oppositely. Moreover, the critical cooling rate to get fully martensitic microstructure increases from 20K/s of static case to 30K/s for 40% deformation amount dynamic case. In addition, the larger the deformation amount is, the much finer lath martensite can be achieved. Furthermore, test results of micro Vickers hardness of the fully martensitic microstructure samples in this study are all above 450HV.

5:35 PM Break