6th World Congress on Integrated Computational Materials Engineering (ICME 2022): On-Demand Oral Presentations
Program Organizers: William Joost; Kester Clarke, Los Alamos National Laboratory; Danielle Cote, Worcester Polytechnic Institute; Javier Llorca, IMDEA Materials Institute & Technical University of Madrid; Heather Murdoch, U.S. Army Research Laboratory; Satyam Sahay, John Deere; Michael Sangid, Purdue University
Monday 7:30 AM
May 2, 2022
Room: On-Demand Session Room
Location: Hyatt Regency Lake Tahoe
Understanding the Interplay between Orientation, Temperature and Lamellar Thickness of Fully Lamellar Titanium Aluminides: A Crystal Plasticity Finite Element Study: Balaji Selvarajou1; Quek Siu Sin1; Mark Jhon1; Raju Ramanujan2; 1Institute of High Performance Computing; 2Nanyang Technological University
Titanium aluminide (TiAl) based alloys are used in aero engine turbines owing to their high strength to weight ratio at the high temperatures experienced during operation. In this work, we investigate the deformation behaviour of a polysynthetically twinned (PST) TiAl/Ti3Al two-phase alloy using crystal plasticity finite element (CPFE) simulations. The constituent phases are described by a crystal plasticity constitutive model taking into account the slip and twin systems in the respective phases. CPFE simulations are used to establish the structure-property linkages between the orientation of the PST, microstructural variables such as lamella width and domain size and the temperature dependent yield strength, including the yield stress anomaly.
Exploration of Microstructural Evolution for Aluminum Alloy Powders through In-Situ TEM and DICTRA Simulations: Kyle Tsaknopoulos1; Matthew Gleason1; Grace Fitzpatrick-Schmidt1; Danielle Cote1; 1Worcester Polytechnic Institute
In solid-state additive manufacturing, it is crucial to control the microstructure of metallic feedstock material, as it directly influences the properties of the final parts. Thermal processing is often used to manipulate the microstructure, tailoring the size, morphology, and distribution of secondary phases for desired material performance. In this study, the heat treatment of Al 6061 powder was explored, with particular focus on phase transformations and diffusion kinetics, for end use in cold spray (CS) applications. In-situ transmission electron microscopy (TEM) heating experiments were leveraged to closely monitor the powder’s microstructural evolution as a function of treatment time and temperature. The time-morphology data of secondary phases obtained from this experimentation can assist with the calibration and validation of DICTRA models. These models will allow for the optimization of heat treatment parameters, prediction of powder microstructures, and understanding of powder heat treatment effects on CS deposition and deposit properties.
Theoretical Model of the Flow Properties of Post Processed Direct Metal Laser Sintering Ti6Al4V: Amos Muiruri1; Maina Maringa1; Willie du Preez1; 1Central University of Technology, Freestate
Heat treatment of DMLS Ti6Al4V(ELI) evinces a wide range of mechanical properties of the alloy depending on the heat treatment cycle adopted. This is due to the different aspects of microstructure such as phase fraction, grain size, texture and dislocation density, that vary with heat treatment. Other external factors, such as prevailing level of strain, strain rate and temperature, also affect the mechanical properties of the material. This paper presents the development of a theoretical model that couples the effects of strain rate, temperature, strain, grain size and initial dislocation density to describe the flow properties of DMLS Ti6Al4V(ELI). According to the model, higher initial dislocation densities result in a higher yield stress, low strain hardening and earlier saturation of flow stress. The model shows that the parabolic shape of the stress strain curve of the alloy is dictated by the initial dislocation density, generally a factor of grain size.
A Multiscale Approach on Strategy to Mitigate Deformation Twinning in Magnesium Alloys: Yubraj Paudel1; Christopher Barrett1; Hongjoo Rhee1; Haitham El Kadiri1; 1Mississippi State University
Deformation twinning in magnesium alloys serves as a “double-edged sword” mechanism while providing easy deformation and strain hardening but resulting in strain-path anisotropy, asymmetry, and damage initiation. In typical texture conditions, twin nucleates at the grain boundaries, propagates along the grain and propagates across the grains through the autocatalysis phenomena. Twin interactions with other twin and slip systems often lead to high strain incompatibilities and, eventually, brittle failure. Strain-energy study through a micromechanics-based solution showed the twin evolution in the strongly textured Mg alloy. Based on experimental and simulation results, we hypothesized that a strong, yet ductile, eutectic surrounding each grain in traditional polycrystals could inhibit twin accommodation effects and thus twin nucleation and autocatalysis mechanisms at grain boundaries. A proof-of-concept experiment on sharply textured magnesium sheets plated with different materials subjected to four-point bending showed the potential of a surface/grain boundary barrier in limiting twinning extent.
A Static and Dynamic Recrystallization Internal State Variable Constitutive Model Based on Microstructures and Its History Effect: Heechen Cho1; Mark Horstemeyer1; 1Liberty University
We present a history-dependent recrystallization material model that unifies static and dynamic effects of recrystallization using continuum Internal State Variable (ISV) constitutive theory. This macroscopic constitutive model includes the recrystallization and grain size variables formulated with structure-property relationships. The recrystallization variable accounts for the evolution of the recrystallized strain-free grains’ volume fraction and its effects on the grain size and mechanical properties at various strain rates, temperatures, and pressures. The novel aspect of this ISV model is that the unification of static-dynamic recrystallization and grain size enables to capture the related mechanical behavior under transient (history-dependent) loading conditions. To demonstrate its history dependence, we validated this recrystallization ISV model against experimental data of sequential loading tests and a multistep manufacturing problem. In these complex boundary value problems, our model, which has been implemented into a finite element code, showed successful agreement with different material’s experimental data.