2023 Technical Division Student Poster Contest: MPMD 2023 Technical Division Graduate Student Poster Contest
Program Organizers: TMS Administration
Monday 5:30 PM
March 20, 2023
Room: Exhibit Hall G
Location: SDCC
SPG-16: A Computer Vision Method of Grain Segmentation for Additive-manufactured Haynes 282 Alloys Under Various Heat Treatments: Yu-Tsen Yi1; Nicholas Lamprinakos1; Junwon Seo1; Anthony Rollett1; 1Carnegie Mellon University
Metal additive manufacturing technology represents a new fabrication method that is able to produce complex geometry components with specific requirements in properties. However, the correlation between the complex geometries of the printed part and microstructural properties, such as grain size distribution, which affects overall performance, is not well understood yet. Here we proposed a computer vision method that can segment out grain and output quantitative numbers of the grain size distribution from scanning electron microscope (SEM) images within seconds, allowing researchers to save significant amounts of time and resources. In this work, we analyze and compare the grain size distribution of additive-manufactured H282 alloy under various heat treatments, hoping to gain a deeper understanding of the relationship between various process parameters and microstructure.
SPG-17: Characterization of Failure Mechanisms for Multimaterial Interfaces Manufactured with Additive Friction Stir Deposition: Cole Franz1; 1University of Tennessee
Additive Friction Stir Deposition (AFSD) exists as a novel solid-state manufacturing process with hopes of repairing damaged non-fusion-weldable materials and building complex structures with wrought-like properties. In this study, aluminum alloys A206 and 6061 are joined together to probe the microstructural evolution at dissimilar material interfaces before and after conventional heat treatment. Due to the solid-state thermomechanical development of complex yet predictable microstructural textures and precipitation mechanisms, this study combines advanced metallographic analysis, spatially resolved diffraction, multi-dimensional mechanical testing, and fractography to elucidate post-process failure mechanisms from joining dissimilar materials via AFSD in order to recommend general process-property relationships for other alloy combinations.
SPG-18: Characterization of Microstructural Heterogeneities in Electron Beam Additively Manufactured Haynes 282: Alivia Mourot1; 1Ohio State University
Additive manufacturing (AM) is being used to fabricate near net shapes of complex geometries with reduced material waste and post-processing. AM process conditions lead to formation of metastable phases with columnar grains resulting in anisotropic mechanical properties. Recently, significant efforts are being directed towards identifying AM processing and post-processing routes to fabricate builds with equiaxed microstructures, even in complex build geometries. Therefore, further research is needed to understand process-structure-property relationships of AM builds. Haynes 282, a precipitation-strengthened Ni-based superalloy, has applications in industrial gas turbine engines due to excellent high temperature creep resistance. In this study, microstructural characterization of a unique pyramidal geometry fabricated by electron beam melting (EBM) was conducted to quantify the size and morphology of the gamma grains, gamma prime precipitates and carbides. SEM and EBSD data were correlated with Vickers hardness maps obtained from different locations of the sample to determine process-structure-property linkages for this geometry.
SPG-19: Comparison of Experimental and Analytical Melt Pool Geometries for High Thermal Conductivity Refractory Metals Using ANSYS: Aditya Rohan Narra1; Venkata Satya Surya Amaranth Karra1; Bryan Webler1; 1Carnegie Mellon University
Studying the melt pool geometry helps in understanding the process space for a successful prints and also helps determine material properties like laser absorptivity. This study examines the melt pool geometries of refractory metals manufactured by powder-feed directed energy deposition and laser powder bed fusion additive manufacturing. Measured cross-sections were compared to predictions from analytical and finite element heat transfer models. Initial microstructure evaluations were also conducted. Initial observations were made of the effects of process parameters on melt pool geometry and printing outcomes for refractory metals.
SPG-20: Correlating Laser Process Conditions to Balling Severity with Time-Resolved Synchrotron X-ray Visualization: John Smith1; Runbo Jiang1; Anthony Rollett1; 1Carnegie Mellon University
There has been a significant interest in maximizing the build rates in laser powder bed fusion additive manufacturing (AM) to increase efficiency and decrease costs. However, while operating at higher scan speeds and powers, the tail end of the melt pool will bead up, placing an upper bound on the process space for producing defect-free parts. In this work, we employ high speed synchrotron x-ray imaging to characterize the bead up phenomenon in Inconel 718 in real time, Working in power ranges of 150-850 Watts and velocity ranges of 500-4000 millimeters per second. It was discovered that there were distinct correlations between process conditions and bead up severity and that a time resolved quantification of the bead up revealed sinusoidal attributes. Ex situ examination of the balling single track microstructures was performed and no detrimental microstructure caused by printing at higher speeds and powers was discovered.
SPG-21: Development of a Generalized Fatigue Assessment Approach for Steel Castings: Matthew Batson1; Brian Jordon1; Paul Allison1; Yu Hong1; 1Baylor University
In this project, a fracture mechanics model is being developed to employ qualities present in steel castings to make fatigue life predictions. Due to conservative restrictions on castings, a simplified approach is needed to determine the quantitative effect casting features have on fatigue life. Samples of 4130 and A487 steel are undergoing tensile, hardness, and fatigue testing followed by post-mortem fractographic analysis of features such as shrinkage porosity and gas pores. This information along with crack growth data and non-destructive evaluation is being analyzed to create a model that incorporates fracture mechanics principles into fatigue prediction. Calculations from the Paris equation show improved correlation when designating discontinuity measurements as initial cracks. Other data and material properties will be incorporated to establish a method of determining a maximum stress value or pore size. This method will then be applied to cast steel literature data to demonstrate its effectiveness.
SPG-22: Effect of Chemical Pretreatment on Properties of Natural Fiber Reinforced Composites for 3D Printing: Athira Nair Surendran1; Sreesha Malayil1; Kunal Kate1; Jagannadh Satyavolu1; 1University of Louisville
Rice husk, soy hulls and corn fiber are some of the largest wastes produced by the grain processing industries in the United States. Currently these biomass are being used as animal feed, combustion and gasification which decrease the market value of these biomass residues as well as increase carbon footprint. We developed a method to utilize residual grain fibers in producing natural fiber composite filaments (NFRC). Different chemical pretreatment methods using acids and alkali were investigated and optimized. Treated fibers were mixed with thermoplastic copolyester (TPC) at 10 wt.% loading and extruded into 3D printing filaments. The 3D printing filaments were analyzed for surface morphology, mechanical properties and printing parameters. The optimization of printing parameters was studied to commercialize and involve other organizations to test the filaments. NFRC was investigated to enhance the mechanical properties while increasing sustainability and decreasing carbon footprint of printed parts.
SPG-23: Effect of Laser Surface Remelting on the Microstructure, Mechanical, Tribological and Corrosion Properties of Bio-applicable Ti40Nb25Zr25Ta10 Medium Entropy Alloy (MEA) with 0.5 at. % O: Labani Mustafi1; Van Thuong Nguyen2; Qiushi Deng1; Lu Jiang3; Adam Taylor3; Tingting Song1; Xiaobo Chen1; Daniel Fabijanic3; Ma Qian1; 1RMIT University; 2University of Queensland; 3Deakin University
Medium-entropy alloys (MEAs) provide a novel design concept for metallic biomaterials. A non-equiatomic bio-applicable as-cast Ti40Nb25Zr25Ta10 MEA with 0.5 at. % O was surface remelted by laser. The consequent effect on the constituent phases, microstructures, mechanical properties, tribological and corrosion resistance properties was investigated. It exhibited a BCC phase after laser surface remelting with a significant decrease in grain size from about 106 μm to 12 μm, accompanied by an increase in hardness from 4.44 ± 0.29 GPa to 7.58 ± 0.15 GPa. Accordingly, the wear rate decreased by 22.5% at applied loads in the range of 200-600 µN load. The corrosion current density of the laser surface remelted MEA (0.007 ± 0.06 µA/cm2) was reduced compared to the as-cast (0.02 ± 0.08 µA/cm2) in Hank’s solution. The improved corrosion resistance is attributed to grain refinement. Laser surface remelted Ti40Nb25Zr25Ta10 MEA with 0.5 at.% O offers a potential candidate for biomedical applications.
SPG-24: Effect of Process Parameters on Texture and Anisotropy of Ti-6Al-4V Wall Components Made by Wire-feed DED Process: Rajib Halder1; Jake Benzing2; Anthony Rollett1; Zhening Yang3; 1Carnegie Mellon University; 2National Institute of Standards and Technology; 3Penn State University
This work explores the effect of processing parameters on texture development in Ti-6Al-4V wall components fabricated by wire-feed Directed Energy Deposition process, one of the additive manufacturing techniques. Microstructure and texture were characterized using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). An open source software package, MTEX, was used to perform grain reconstruction, orientation analysis, variant selection analysis, and generate IPF maps. A viscoplastic self-consistent (VPSC) model was used to simulate the deformation response under uniaxial tension applied along vertical, horizontal, and diagonal directions with respect to the build direction of the single wall component. A strong variation in texture was observed along the build direction in laser hot wire deposited single walls. VPSC simulation confirmed the tension-compression asymmetry and the anisotropic response of Ti-6Al-4V single walls. The horizontal stress was found to be higher as compared to vertical and diagonal stresses.
SPG-25: Effects of the Reduction Temperature and Amount of Diluent on the Properties of High-purity Tantalum Powder Prepared via the Hunter Process: Yongkwan Lee1; Sunggue Heo1; Jae-Jin Sim2; MiHye Lee2; Soong Ju Oh1; JaeHong Shin2; Kyoung-Tae Park2; 1Korea University; 2Korea Institute of Industrial Technology
The Hunter process is predominantly used to manufacture high-purity Ta powder. In this study, the process temperature at which a liquid pool of raw material and diluent can be formed and the corresponding amount of diluent were analyzed by performing thermodynamic simulations using FactSage software. Based on the results of the thermodynamic simulations, Ta powder was prepared at process temperatures of 700–800 °C and a specific amount of NaCl at each temperature. Thereafter, the prepared Ta powder was recovered and a post-treatment process was performed to ensure purity. The synthesized Ta powders were confirmed to exhibit purities greater than 99.95% and oxygen, nitrogen, and hydrogen concentrations of 447, 21, and 10 ppm, respectively. The characterization results indicated that the produced Ta powders were fabricated entirely in a single phase with high purity and recovery rates. Finally, process optimization was achieved for manufacturing high-purity (≥3N5) Ta powder with controllable impurities.
SPG-26: Effects of Varying Heat Accumulation in Laser Powder Bed Fusion on Microstructure Outcomes in Ti-6Al-4V: Evan Adcock1; 1Carnegie Mellon University
The fast temperature changes in laser powder-bed fusion impact the microstructure of the material being printed; likewise, part geometry and printing parameters will affect the overall temperature history. To investigate this phenomenon in Ti-6Al-4V, two “inverted pyramids” were printed with a specific geometry to generate variability in thermal history within the part. One pyramid was printed as normal while the other had an intentional delay between layers to allow more cooling. The microstructure outcome has been analyzed by backscatter scanning electron microscopy and X-ray diffraction. Microhardness tests have also been conducted across large sections to probe the mechanical property variation in relation to observed microstructure. Simultaneously, temperature simulations are being performed for comparison with in-situ build data and further analysis of the microstructure with a process prediction model. Microstructure and property trends within each build have been found relative to the overall heat accumulation at different layers.
SPG-27: Evaluating the Effect of Tool Offset on Repaired AA7050 by Additive Friction Stir Deposition: Victor Rojas1; Ismael Hidalgo1; J. Brian Jordon1; Paul Allison1; 1Baylor University
This study evaluates the viability of repairing simulated damaged AA7050 plates and the effect of implementing a tool offset with Additive Friction Stir Deposition (AFSD). During deposition, the simultaneous rotational and transverse motion of the toolhead causes an asymmetrical response of the flowing deposited material. This asymmetrical effect was studied by isolating each side by performing depositions at different offsets and at different sides from the groove centerline. The research will provide insight on the relevance of such parameter when implementing repairs with AFSD and the general post repair mechanical performance. Vickers microhardness measurements were performed to observe how the heat affected zone (HAZ) is influenced by the offsets. Monotonic tests were carried out to compare the AFSD repaired specimens from the original damaged specimens. The results suggest that repairs with AFSD on AA7050 is a viable solution to salvage damaged parts.
SPG-28: Evaluation of As-deposited Tensile Behavior and Microstructure of Additive Friction Stir Deposition 304L Stainless Steel: Jessica Lopez1; 1University of Alabama
This research investigates the as-deposited microstructure and tensile behavior of multi-layer 304L stainless steel additive friction stir deposition (AFSD) builds. Tensile specimens were machined from 7 layer AFSD builds consisting of 0.5 mm individual layer heights, 30 mm layer widths, and 76 mm long. The AFSD 304L stainless steel deposit showed tensile strengths similar to wrought stainless steel, as well as uniform hardness throughout the layers and substrate. Characterization of the AFSD deposit revealed equiaxed grain structure compared to the substrate. Oxide formation was observed at the layer interfaces, which resulted in lower build-direction tensile ductility. The present study demonstrates AFSD technology as an emerging large scale solid-state, non-melting, additive manufacturing process building 304L stainless steel components.
SPG-29: In Operando Synchrotron X-ray Tomography Study of Fine Eutectic Polyphase Solidification Patterns: Paul Chao1; George Lindemann1; Shanmukha Aramanda1; Ashwin Shahani1; 1University of Michigan
Eutectics are a paradigm of natural composite materials consisting of two, entangled single-crystal phases. The simultaneous crystallization of two solid eutectic phases creates highly ordered patterns of remarkable complexity. One or both of the solid phases may possess a strong anisotropy of interfacial energy and/or mobility with respect to the liquid phase, which leads to a faceted growth front. These effects have been hypothesized to influence the coupling of the solute diffusion fields ahead of the composite eutectic growth front and thus modify the resulting two-phase pattern that solidifies. Here, I leverage state-of-the-art synchrotron-based in-situ x-ray tomography to visualize in unprecedented detail the growth trajectories of both eutectic solids in four-dimensions (i.e., three-dimensional space plus time). We compare against classical theories, specifically how pattern selection mechanisms are governed by crystalline anisotropy and growth velocity. These experimental results can inform development of complex multiphase materials with unique mechanical or electrical properties.
SPG-30: Induction-Coupled Thermomagnetic Processing of Fe-C Alloys: Megan Hurley1; Ramon Padin-Monroig1; Benjamin Begley1; Zach Tener2; Steven Flynn1; Mike Kesler3; Michele Manuel1; Mark Meisel1; Victoria Miller1; 1University of Florida; 2Oak Ridge National Laboratory ; 3Oak Ridge National Laboratory
The current state-of-the-art processes used for steel heat treatments are highly energy intensive and environmentally damaging. Innovative induction-coupled thermomagnetic processing (ITMP) is a promising, energy-efficient alternative, where the incorporation of a high static magnetic field alters the phase equilibria and transformation kinetics of steel in such a way that it can improve microstructural and mechanical properties. Literature indicates alterations in the solubility of carbon, but the information available is insufficient to engineer improved steel heat treatments. The current investigation uses diffusion couple experiments and electron backscatter diffraction to examine the phase development and morphology of martensite and pearlite in binary Fe-C alloys processed under varied temperatures and fields. In addition, the role of the field in microstructure development and diffusion kinetics is discussed.
SPG-31 Laser-Powder Bed Fusion of Ti-6Al-2Sn-4Zr-2Mo-0.08Si (Ti-6242): As-built Properties, Kinetics of α to β Phase Transformation, and Design of Heat Treatment: Harish Kaushik1; Mahdi Habibnejad Korayem2; Amir Hadadzadeh1; 1University of Memphis; 2AP&C Advance Powder and Coating, a GE Additive Company
Ti-6242 is a near-α high-temperature titanium alloy. As a near-α alloy, the evolution of the β phase with different volume fractions and morphologies will affect the strength and ductility. On the other hand, laser powder bed fusion (L-PBF) has enabled the fabrication of metals with ultrafine, metastable, and hierarchical microstructures. Such microstructures contribute to strength and ductility through distinct mechanisms at different length scales. In this study, Ti-6242 is fabricated using L-PBF with different energy densities. The kinetics of α to β phase transformation in the L-PBF samples is then studied using differential scanning calorimetry (DSC). The kinetics results are used to design a two-step heat treatment to enhance the ductility at minimal strength loss, through the evolution of the β phase with various volume fractions and morphologies. The microstructure is studied using multi-scale techniques including OM, SEM, EBSD, and TEM to elaborate on the mechanisms of strengthening and toughening.
SPG-32: Melt-pool Dynamics during Multiple-laser-beamed Powder Bed Fusion of Stainless Steel: Marco Rupp1; Shuichiro Hayashi1; Claire Dashe1; Wenxuan Zhang1; Craig Arnold1; 1Princeton University
Laser-based Powder Bed Fusion (L-PBF) is an emerging additive-manufacturing technique capable of creating complex structures with high resolution out of metal powders. However, current limitations in the processing speeds and resulting microstructures have hindered the advancement of L-PBF. In this study we have devised a multiple-laser beam setup and investigated the fundamental implications of using a multiple-laser setup. For the experiments, two 1064-nm Nd-YAG-lasers operating in the continuous-wave mode were focused onto a layer of 316L stainless steel powder. When the two laser beams were scanned in parallel at a specific parameter range, a new melt-pool regime displaying a periodic pattern appeared. This pattern was attributed to be a result of the growth and decline of the melt-pool due to the Rayleigh-plateau instability. Additionally, we were able to link the geometry of the melt-track to the energy input and melt-pool dynamics.
SPG-33: Modeling for Time Dependent Grain Boundary Evolution: Lucero Lopez1; Elizabeth Holm1; 1Carnegie Mellon University
Analysis of grain boundary evolution is a critical step in understanding the relationship between microstructure and material properties. In experimental analysis we can see microstructure evolution in metals influences thermal-mechanical properties such as strength, hardness, and thermal and electrical conductivity, making the study of grain boundaries essential in Material Science. Computational simulations allow materials scientists to study the models that capture these phenomena. Our method is to compare three mesoscale models: Kinetic Monte Carlo, Probabilistic Cellular Automata, and Phase Field simulations for modeling grain growth and shrinkage, first in 2D and then 3D evolution. By comparing the uncertainty in grain lifetime in each of these models, the nature of grain evolution can be better understood. In particular, we begin to quantify how sensitive a microstructural outcome (grain disappearance) is to the details of the initial conditions. This helps bolster the relationship between grain structure and material properties.
SPG-34: Multi-scale In Situ Studies of Deformation Mechanism of L-PBF 316L Stainless Steels: Wanxuan Teng1; Biao Cai1; Moataz Attallah1; 1University of Birmingham
In situ synchrotron x-ray diffraction and tomography were used to study deformation mechanisms of 316L stainless steels produced by laser powder bed fusion (LPBF). We identified the formation of corrugated surface in LPBF 316L stainless steel during tensile testing via in situ tomography, confirmed by ex situ optical imaging and surface roughness measurement. The formation of corrugated surface might be attributed to the grain structure formed from the LPBF process. The porosity was found to become elongated during loading, leading to the failure of the specimen. The findings show further potential for optimization of mechanical performance of additive manufactured alloys through adjusting the microstructure.
Cancelled
SPG-35: Multi-scale Modelling for Material Design in Additive Manufacturing: Weiling Wang1; Wei Wen1; Hossein Eskandari Sabzi1; Pedro Rivera-Diaz-del-Castillo1; 1Lancaster University
Additive manufacturing (AM) processing-induced microstructure exerts a significant influence on the deformation behaviour of SS316L. Interestingly, the existence of nano-sized pores shows a limited effect on the SS316L mechanical properties, especially the creep deformation. In this work, crystal plasticity finite element method (CP-FEM) simulations are carried out based on the grain mapping that represents the AM-induced microstructural features. A physics-based plasticity model combined with the classic Gurson-Tvergaard-Needleman (GTN) damage model is implemented in a CP-FEM framework to predict the local mechanical response during the creep deformation. This work shows that AM-related dislocation structures can provide a shielding effect and enable higher strength tolerance around the pore.
SPG-36: On the Influence of Gaussian and Ring-shaped Beam Profiles on Quality and Energy Consumption in L-PBF of Inconel 718: Ersilia Cozzolino1; Austin Tiley1; Edward D. Herderick1; 1Center for Design and Manufacturing of Excellence, The Ohio State University
Additive Manufacturing (AM) has the potential for improving the sustainability of metal processing through decreased energy and materials usage compared to casting and forging. Laser powder bed fusion (L-PBF) of high-temperature alloys such as nickel alloy 718 is one of the key modalities supporting this effort. One of the major drawbacks to L-PBF is its slow build speed on the order of 5-10 cubic centimeters per hour print speed. Our team is investigating speeding up L-PBF printing 10x by switching from a traditional Gaussian laser shape to a ring laser shape using a nLight multi-modal laser. The objective is to increase productivity dramatically while only marginally increasing energy consumption by switching to the ring laser thereby improving the sustainability of L-PBF. Results include measuring the energy consumption of an Open Additive L-PBF system during the Inconel 718 printing and comparing the microstructure and mechanical properties of the two different lasers.
SPG-37: Oxide Morphology and Growth Kinetics for Additively Manufactured 316L Austenitic Stainless Steel High Temperature Steam Exposures: Scott Schier1; Katherine Montoya1; Allyssa Bateman2; Ethan Schneider1; Elizabeth Sooby1; Brian Jaques2; 1UTSA; 2Boise State University
Additive manufacturing (AM) has been proposed as a multifaceted approach to high throughput and material characterization and testing to relate print parameter, print orientation, sample, and thermal histories to relevant nuclear reactor performance properties. Continuous research in AM has propelled it to revolutionize the manufacturing industry due to the unparalleled design flexibility of the build process that allows rapid innovation of complex parts. Reactor parts are required to meet structural material qualifications meaning AM parts must be able to withstand off-normal reactor events involving steam exposure, in light water reactors as well as some advanced reactor designs. This study presents the characterization of oxidized AM 316LSS when exposed to high temperature (600°C<T<1000°C) steam (<65% pH2O) atmospheres. Raman spectroscopic analysis determines the chemical composition of the polished/passivated surface oxides that form on samples. Scanning electron microscopy provides microstructural characterization of surface and cross-sectional features of the oxide films and pitting defects.
SPG-38: Printability and Defects in W & W -alloys by Directed Energy Deposition: Amaranth Karra1; Bryan Webler1; 1Carnegie Mellon University
This study examines microstructure and mechanical properties ofpure tungsten and tungsten alloys additively manufactured by powder-feed directed energy deposition additive manufacturing. Cubes were deposited on a refractory metal baseplate. The layer height was experimentally decided as a function of powder,travel speed, and powder feed rate by the quantification of already printed cubes. The microstructure and cracking of the tungsten & tungsten alloy cubes was also assessed and the cause for porosity in the samples using DED process was studied. Results showed how alloying and process parameter selection can lead to reduction in defects during direct energy deposition of tungsten and its alloys.
SPG-39: Recycled Battlefield Titanium Scrap for Cold Spray Applications: Kiran Judd1; 1Worcester Polytechnic Institute
This work explores the potential utility of on-demand recycled titanium feedstock powder for “in the field” cold spray repair to better support the warfighter while also decreasing equipment and part downtime. The titanium scrap was atomized from three different grades of titanium using a mobile foundry manufactured by MolyWorks Materials Corporation. Characterization of the three titanium powders was used to optimize cold spray parameters for maximum coating deposition and part quality. The powder and sprayed specimens were characterized using microscopy, particle size distribution (PSD) analysis, powder rheometry, particle compression, Karl Fischer Titration moisture analysis, ONH element analysis, profilometry-based indentation plastometry (PIP), and nanoindentation. Computational thermodynamics and kinetic models were used to guide heat treatment selection for thermal post-processing liquid phase sintering to improve properties of selected consolidated samples. Preliminary results display similar powder particle size, shape, texture, and morphology across recycled powder types.
SPG-40: Removal of Rare Metal Impurities by Electron-beam Melting Refining Process: SungGue Heo1; YongKwan Lee1; Hyunchul Kim1; Seok-Jun Seo1; KyoungMook Lim1; SoongJu Oh1; Kyoung-Tae Park1; 1Korea Institute of Industrial Technology
Since the Electron Beam Melting (EBM) refining process, used for the smelting of rare metals, proceeds the removal of impurities in high temperature metals, to have an efficient ingot production through this process, the correlation of the specific removal of impurities in rare metals, according to electron beam energy density calculation through calculating the output of the electron beam with a numerical analysis approach, should be analyzed. In addition, it is necessary to optimize electron beam parameters for high purity of rare metals. In this study, the beam trajectory and energy were calculated by controlling the beam output of the electron beam gun through finite element analysis, and through this, the temperature distribution of the material was confirmed. In addition, to have calculated partial pressure of impurities that is use of the Vapor Liquid Equilibrium (VLE) in the Computer Coupling of Phase Diagrams and Thermochemistry (CALPHAD).
SPG-41: Strain Evolution and Damage Development during Tight-radius Bending of Advanced High Strength Steels: Nizia Mendes Fonseca1; David Wilkinson1; 1McMaster University
Advanced High Strength Steels (AHSS) are recognized for their excellent trade-off between uniform tensile elongation and strength. However, tensile ductility fails to predict damage initiation during local forming operations required to fabricate complex automotive parts, which involve tight-radius bending and edge stretching. Therefore, it is crucial to understand how the microstructure of AHSS affects their behavior in tension and tight-radius bending. This work experimentally investigates a dual-phase (DP) and a quench and partitioning (QP) steel under bend loading at the macro and microscales. The methodology includes digital image correlation, in situ SEM testing, and X-ray computed microtomography. Results show that the main micromechanisms leading to damage are interface decohesion, resulting from a strain gradient at the phases interface, and cracking of martensite. Damage and fracture are delayed in the QP steel due to the better mechanical compatibility of its constituents and the effect of transformation-induced plasticity.