Phase Transformations and Microstructural Evolution: Structure and Properties
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Ashley Paz y Puente, University of Cincinnati; Mark Aindow, University of Connecticut; Sriswaroop Dasari, Idaho National Laboratory; Ramasis Goswami, Naval Research Laboratory; Megumi Kawasaki, Oregon State University; Eric Lass, University of Tennessee-Knoxville; Joshua Mueller, Michigan Technological University; Eric Payton, University of Cincinnati; Le Zhou, Marquette University
Thursday 2:00 PM
March 23, 2023
Room: 25C
Location: SDCC
Session Chair: Le Zhou, Marquette University
2:00 PM
Precipitate Size Distribution Evolution in an Additively Manufactured High Temperature Al-Cr-Zr Alloy: Darby Laplant1; J. Hunter Martin1; Tresa Pollock2; 1Hrl Laboratories, LLC; 2University of California, Santa Barbara
Non-equilibrium processing pathways, particularly additive manufacturing, have broadened the scope for alloy design, often resulting in unique microstructures and properties. Understanding these as-fabricated microstructures, as well as their kinetic evolution and phase transformation due to thermal processing is essential to deepen understanding of new alloys and optimize their properties for industrial service. This talk will focus on the analysis of an additively manufactured Al-Cr-Zr alloy, for high temperature (150-350C) applications, to better understand its as-fabricated and heat-treated microstructure. Small- and wide-angle X-ray scattering spectra are utilized to determine the temporal evolution of the temperature stable, strengthening precipitates in this alloy, focusing on their size distribution and phase structure during in situ heat treatment with correlation to resulting mechanical properties.
2:20 PM
Microstructures in Icosahedral-Phase-Strengthened Aluminum Alloy Powders for Additive Manufacturing: Mingxuan Li1; Sarshad Rommel1; Thomas Watson2; Callie Benson3; Rainer Hebert1; Mark Aindow1; 1University of Connecticut; 2Pratt & Whitney; 3Collins Aerospace
Recently, we have developed a series of Al-Cr-Mn-Co-Zr alloys that exhibit nano-composite microstructures in gas-atomized powders. The microstructures comprise an FCC Al matrix with quasicrystalline I-phase dispersoids. The morphology and distribution of the I-phase varied with the particle size due to changes in nucleation mechanisms with cooling rate. The I-phase was retained during consolidation of the powder to form bulk alloys, and the resultant materials exhibited excellent mechanical properties and corrosion resistance. The properties indicate that there is significant potential for the use of this alloy system in metal additive manufacturing. Here we present microstructural data obtained from powders of a new Al-Cr-Mn-Co-Zr alloy whose composition has been modified specifically for use in additive manufacturing. The variation in the I-phase dispersoid morphology and distribution with particle size is compared with that observed in earlier alloy formulations, and the effects of microstructure on the character of the surface oxides is discussed.
2:40 PM
Thermal Stability of Quasicrystals in a Candidate Al Alloy for Additive Manufacturing: Baris Yavas1; Mingxuan X. Li1; S. Pamir Alpay1; Mark Aindow1; 1University of Connecticut
Metal additive manufacturing (MAM) has attracted intense interest for a wide variety of industrial applications. One of the more novel material types that is under consideration for MAM is quasicrystal (QC) reinforced metal matrix composites (MMCs). In this study, we evaluated an Al-Cu-Fe-Cr alloy, which contains a dispersion of icosahedral QCs. Laser glazing studies have been performed to evaluate the potential for using this alloy in additive manufacturing, and QC formation was observed over a wide range of processing parameters. Since the QC reinforcement phase is inherently metastable, it is important to understand the mechanism and conditions for the thermal decomposition (crystallization) of this phase. In situ transmission electron microscopy heating studies can provide unique insights into such processes. Here we report in situ isothermal heating studies performed at between 350-500 °C on the laser-glazed materials to reveal the thermal stability and decomposition products of the QC dispersions.
3:00 PM
Physics-based Simulations of Microstructural Evolution Using Graph Theory: Iman Javaheri1; Veera Sundararaghavan2; 1NASA Langley Research Center; 2University of Michigan
A novel physics-based numerical framework based on graph-theoretic techniques is presented for the microstructure evolution of ceramic materials. The primary driving force for crystal formation, precipitate coarsening, and grain growth in the ceramic microstructures is the reduction of orientation-dependent surface free energies. As a result, the equilibrium shape of the crystalline structure (i.e., Wulff construction) can be precisely determined by minimizing its surface free energy. Here, an energy optimization principle based on the Cauchy-Crofton formulation, which embodies the underlying energetic mechanisms of grain boundary (GB) formation, is developed to find the global minimum facets (Wulff shape) in 2D/3D domain for a given set of Riemannian metrics. The efficacy of the proposed technique is demonstrated in several case studies and compared against data from in-situ high-energy tomography techniques.
3:20 PM Cancelled
A Self Consistent Phase Field Crystal Plasticity (CPPFM) Approach in the Realm of Small and Large Deformation Framework: Tariq Ali1; Soumya Bandyopadhyay1; Hyung-Uk Jang1; Pil-Ryung Cha1; 1Kookmin University
This work aims to establish a correlation between phase transformation and deformation by coupling crystal plasticity and phase-field method (CPPFM). Initially, we implement CPPFM in the realm of a small perturbation framework and finally proceed towards the large deformation approach. We start with the implementation of rafted morphologies (often encountered in Ni-based superalloys) and compare the mechanical behaviour during the elastic and combined elastic-plastic deformation. We observe more elongated microstructures in the elasto-plastic case, which we attribute to the higher stress relaxation compared to the other case. The simulated stress-strain curve agrees well with that of the experimental statistics. Later, we proceed to the finite deformation approach, where we attempt to study the microstructure and texture evolution in polycrystalline FCC metals subjected to uniaxial compression. Our predicted texture morphology agrees well with the available experimental observations as well as commercially available FEM based softwares.
3:40 PM Break
4:00 PM
Fatigue Properties of Microstructural Gradients in Ti-6Al-4V Generated with Thermohydrogen Treatment: Christopher Dav Schmidt1; Hans-Jürgen Christ1; Axel von Hehl1; 1University of Siegen
Structural components must fulfil the demand of saving resources by lightweight design without losing reliability. Hence, improved processing techniques for commercial materials must be developed. One approach is to charge the Ti-6Al-4V temporarily with hydrogen (thermo-hydrogen treatment, THT) generating lattice distortion and hydrides. The resulting localized plastic deformation potentially triggers recrystallization and enables a finer microstructure than that which can be attained by a conventional heat treatment. The study presented aims at the design of a THT process that establishes a microstructure with a local change in distribution and morphology of strengthening precipitates and grain size as a function of the distance to surface (microstructural gradient).To evaluate the mechanical properties of microstructural gradients produced in a previous work the resulting Wöhler curves were determined by stress-controlled cyclic deformation tests. The results show that H-charging at 500°C and H-degassing at 750°C improves the fatigue properties compared to a reference condition.
4:20 PM Cancelled
Micro-beam Diffraction of Nano-structured Severe Plastically Deformed Metals Following Their Structural Evolution upon Heating: Klaus-Dieter Liss1; Xiaojing Liu1; Jae-Kyung Han2; Malte Blankenburg3; Megumi Kawasaki2; 1Guangdong Technion - Israel Institute of Technology (GTIIT); 2Oregon State University; 3Deutsches Elektronen-Synchrotron (DESY)
Nano-structured metals as obtained by severe plastic deformation, especially high-pressure torsion (HPT), expose novel mechanical and physical properties due to the metastable nano-grained microstructure and stress states. We have undertaken high-energy micro-beam diffraction at Petra‑III upon heating various HPT-processed alloys to evaluate the regimes of recovery, recrystallization and grain growth. Besides the evaluation of lattice strain and peak widths, the azimuthal-time evolution of sharpening single-crystallite reflections expose deep insight into the relaxation processes.
4:40 PM
Evolution of Phases and Interfaces in Self-healing Composites Made of Al5083 Matrix and Encapsulated ZnAl Particles: Baolong Zheng1; Xin Wang1; David Svetlizky2; Lorenzo Valdevit1; Noam Eliaz2; Enrique Lavernia1; Julie Schoenung1; 1University of California, Irvine; 2Tel-Aviv University
Self-healing materials have the capability to repair cracks generated in the components under external stimuli, such as heat, solvents, deformation, etc. Aluminum alloy matrix composites containing encapsulated ZnAl particles have been designed by Svetlizky and Eliaz as metallic self-healing materials. Here, we report on the investigation of Al5083 based composites reinforced with core-shell ZnAl/Co particles consolidated using spark plasma sintering (SPS). The phase transition and interface between the Co shell coating and the ZnAl core plays an important role in determining the integrity, diffusion, and self-healing ability of encapsulated ZnAl. To gain better understanding of the self-healing function of the Al5083 + ZnAl/Co composite, the interface evolution and phase transition around the coating and the cracks after self-healing were investigated using (scanning) transmission electron microscopy (S/TEM) and X ray diffraction (XRD). The microstructure evolution is also rationalized based on the thermal history during SPS sintering and self-healing heat treatment processing.
5:00 PM
Phase-field Modeling of Interaction Between Phase Transformation and Cracking in Shape Memory Ceramics: Amirreza Lotfolahpour1; Mohsen Asle Zaeem1; 1Colorado School of Mines
We present a modified phase-field model to investigate the phase transformation and cracking in shape memory ceramics. The chemical free energy is modified to solve a problem of existing models in underestimating the elastic response at the beginning of the stress-strain curve. First, the modified model is tested for microstructure and mechanical response predictions in a super-elastic 3 mol% yttria-stabilized tetragonal zirconia without considering fracture. Then, the interaction between phase transformation and fracture under displacement-controlled loading condition is investigated. The results are validated against experimental results in terms of microstructure and crack path predictions. The proposed model predicts a realistic mechanical response and the experimentally observed microstructure and crack deflection due to the phase transformation. In addition, the model captures the reverse phase transformation, the effect of grain orientation, and the stress drop due to the crack propagation.