Interactions of Phase Transformations and Plasticity: Session 1
Program Organizers: Valery Levitas, Iowa State University

Monday 10:40 AM
July 10, 2017
Room: Water Tower
Location: Hyatt Regency Chicago

Session Chair: Valery Levitas, Iowa State University

10:40 AM  Invited
Phase Transformations Induced by Severe Plastic Deformation: Alexander Zhilyaev1; 1Fundaciˇ CTM Centre Tecnol˛gic
    In recent years, the development of bulk nanostructured materials (BNM) has become one of the most fascinating directions in modern materials science. During the last two decades, severe plastic deformation (SPD) techniques have attracted special interest not only for grain refinement but also for inducing phase transformation and for “freezing” this metastable state after releasing high pressure. The generation of new and unusual properties has been demonstrated for a wide range of different metals and alloys: examples include very high strength and ductility, record-breaking fatigue endurance, increased superplastic forming capabilities as well as multifunctional behavior when materials exhibit enhanced functional (electric, magnetic, corrosion, etc.) and mechanical properties. Present report is an overview of latest progress in generating nanostructure of metals and alloys underwent phase transformation under SPD with enhanced mechanical and functional properties. Some examples of phase transformations (including topological one) will be discussed.

11:20 AM  
Simulation of Effect of Phase Transformation on Material Deformation Textures: Shivram Kashyap Sridhar1; Anthony Rollett1; 1Carnegie Mellon University
    Phase transformation between B2 austenite and B19' martensite characterize the Shape memory and Superelastic properties of Nickel Titanium (NiTi). The superelastic properties make NiTi a suitable candidate for minimally invasive biomedical devices. However, this transformation also plays an important role in determining cold working crystallographic textures. In this work we try to incorporate martensitic transformations as a deformation mode in the ViscoPlastic Self Consistent (VPSC) simulations. VPSC is a micromechanical model based algorithm that solves the anisotropic Eshelby inclusion in a Homogeneous Effective Medium (HEM) problem. We try to explore the effect of simultaneous slip activity in austenite and martensitic transformations on plastic response of the material. We shall try and compare our simulation results with the experimental results observed in literature and from our work.

11:35 AM  
The TRIP Effect of Austenitic Steels under Multiaxial Loading: Wei-Neng Hsu1; Efthymios Polatidis2; Tobias Panzner3; Miroslav Smid2; Helena Van Swygenhoven1; 1Swiss light source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland/Neutrons and X-rays for Mechanics of Materials, IMX, Ecole Polytechnique Federale de Lausanne, CH-1012 Lausanne, Switzerland; 2Swiss light source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland; 3Laboratory for Neutron Scattering, NUM, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
     The deformation-induced martensitic transformation in TRIP steels has been mainly studied upon uniaxial deformation. A few studies point towards a disagreement in whether transformation is facilitated or retarded under multiaxial stress-states or strain path changes. Using a biaxial deformation-rig installed at the neutron strain-scanning beamline POLDI of the Swiss neutron spallation source (SINQ), the influence of proportional and non-proportional loading on the transformation behavior of a metastable austenitic stainless steel (Type 304) was studied.The in-situ diffraction measurements carried out during uniaxial, equibiaxial deformation and strain path changes provide insights to the microstructural and phase evolution, the distribution of internal stresses in the phases and the residual stress after unloading. Post-mortem microstructural characterization of the morphological changes induced by the deformation, (e.g. shear-band formation, deformation-induced twinning etc.) are correlated to the results obtained from in-situ techniques and discussed with respect to the nature of the deformation.

11:50 AM  
TRIP Effect in a Constant Load Creep Test at Room Temperature: Noriyuki Tsuchida1; Stefanus Harjo2; 1University of Hyogo; 2Japan Atomic Energy Agency
    In order to investigate TRIP (transformation induced plasticity) effect in different deformation style, a room temperature creep test under the constant load was conducted by using a TRIP-aided multi-microstructure steel. As a result, the volume fraction of deformation-induced martensite in the constant load creep test was larger than that in the tensile test. In-situ neutron diffraction experiments during the constant load creep test were performed to discuss its reason. The lattice plane strains of austenite and ferrite phases obtained by the neutron diffraction experiments are independent of <hkl> grain families whereas those by the tensile test depend on <hkl> grains. The deformation-induced martensitic transformation behavior in the both test are discussed from the viewpoints of such the differences of lattice strains or intergranular stress.

12:10 PM Break