4th World Congress on Integrated Computational Materials Engineering (ICME 2017): ICME Success Stories and Applications - III
Program Organizers: Paul Mason, Thermo-Calc Software Inc.; Michele Manuel, University of Florida; Alejandro Strachan, Purdue University; Ryan Glamm, Boeing Research and Technology; Georg J. Schmitz, Micress/Aachen; Amarendra Singh, IIT Kanpur; Charles Fisher, Naval Surface Warfare Center

Thursday 8:00 AM
May 25, 2017
Room: Salon IV
Location: Ann Arbor Marriott Ypsilanti at Eagle Crest

8:00 AM  
Integrated Experimental and Computational Studies of Non-conventional Transformation Pathways in Titanium Alloys: Yufeng Zheng1; Rongpei Shi1; Deep Choudhuri2; Talukder Alam2; Robert Williams1; Rajarshi Banerjee2; Yunzhi Wang1; Hamish Fraser1; 1The Ohio State University; 2University of North Texas
    The precipitation of hcp alpha phase in bcc beta phase matrix is critical for titanium alloys due to its significant influence on mechanical properties. The nucleation of alpha phase can be affected strongly by the compositional and/or structural instabilities within the beta matrix and so may follow non-conventional transformation pathways. In this research, the pathways for refined and super-refined intragranular precipitation of the alpha phase in Ti-5Al-5Mo-5V-3Cr (Ti-5553) were studied coupling advanced modern characterization techniques and powerful computational simulation. Experimental results indicate clearly that during the as-quenched condition Ti-5553 being heated up rapidly to the ultimate aging temperature (600C), refined alpha microstructure is produced in beta matrix by pseudo-spinodal decomposition mechanism in which large number of solute lean regions formed by thermal compositional fluctuation act as favorable sites of alpha precipitation. While on the other hand, during as-quenched condition Ti-5553 being heated up slowly, the pre-formed large number of nano-scale isothermal omega phase particles can assist subsequent super-refined alpha precipitation. Computational simulation using phase field modeling based on structural and compositional information obtained from experiment shows that the presence of such fine scale compositional and/or structural instabilities due to pre-formed solute lean region or the omega phase particles can modify the compositional and stress field in the parent beta matrix and therefore provide an additional driving force, and nucleation site, for alpha precipitation. A detailed understanding of non-conventional transformation pathways controlling refined and super-refined alpha microstructure in Ti-5553 will be described.

8:20 AM  Invited
ICMSE for Titanium: A Status Report: Dipankar Banerjee1; John Allison2; 1Indian Institute of Science; 2University of Michigan
    We examine in this presentation the current status of integrated computational materials science and engineering (ICMSE) of titanium alloys. We first explore the scientific core of computational materials science underlying various key phenomena that characterize the metallurgy of titanium alloys, within an integrated multiscale framework. Significant gaps in physics-based models continue to exist even as models evolve towards a greater computational and simulation capability. We then examine efforts directed towards the prediction of engineering properties that links key ingot to billet conversion process variables, microstructure and texture, and mechanical properties. These efforts are based on extraction of location-based data sets of strain, strain rate, and temperature that influence the evolution of structure and microtexture from billet to final forged samples. Engineering titanium alloys are largely based on relatively coarse two-phase bimodal stress. Stress and strain partitioning and crystal plasticity methodologies are used to model microstructure, texture and microtexture. Finally neural network methods predict property dependence using statistically characterized relationships. We note that computational materials science efforts for intermetallics of titanium alloys based on gamma aluminide are currently not extensive. Finally we describe current efforts directed at evolving towards next generation ICMSE tools that include integrated multiscale modeling frameworks, uncertainty quantification, rapid and quantitative experimental capabilities, information infrastructure and industry ready open source software for rapid insertion of new science.

8:40 AM  
Through Process Modelling of Microstructure Development in AA6082 Extrusion Alloys: Warren Poole1; Mary Wells2; Nick Parson3; Jingqi Chen1; Yahya Mahmoodkhani2; 1The University of British Columbia; 2University of Waterloo; 3Rio Tinto Aluminium
    There is a complex interplay between the various processing steps in aluminum extrusion production which affect the properties of the final extrudates in service. For example, the role of microstructure development during homogenization has important effects on the grain structure of as-extruded products. This study is concerned with the variation of grain structure (including crystallographic texture) through the thickness of the extrudate and how this can affect the anisotropy of the mechanical response. It will be shown that by using finite element method models, the deformation path can be tracked as the material moves through the die and exits. This deformation path controls the formation of deformation and possible recrystallization textures which spatially vary through the thickness of the extrudate. In this work, extrusion trials have been conducted on AA3003 with a very high density of dispersoids to minimize recrystallization during extrusion and on conventional AA6082 to examine an industrially relevant alloy. The deformation texture at the centre and surface of the extrudate can be rationalized by the strain path the material follows as it passes through the die. In addition, it is found that details of the die geometry affect the surface layer and possible formation of a peripheral coarse grain (PCG) region. This has been rationalized by detailed EBSD, finite element method models and crystal plasticity calculations.

9:00 AM  
ICME Approach to Microstructural Design of Corrosion-Resistant Aluminum Alloys: Kenneth Smith1; John Allison2; James Beals1; Rudolph Buchheit3; Gerald Frankel3; Lori Flansburg4; Jacquelynn Garofano1; Mark Jaworowski1; Jenifer Locke3; Amit Misra2; Anna Paulson4; Rajiv Ranjan1; Brian Said4; Christopher Taylor5; Katsuyo Thornton2; 1United Technologies Research Center; 2University of Michigan; 3The Ohio State University; 4Lockheed Martin; 5DNV GL
    Corrosion costs the U.S. over $1 trillion annually, yet is typically not analyzed at a detailed level during the product design phase. We are developing an ICME toolset to relate microstructure with corrosion performance for aluminum alloys that enables corrosion assessment in the design process. This effort combines modeling and experiment to ultimately provide risk assessment and service life predictions, combined with mechanical prediction models, to demonstrate microstructural design optimization. The current foci are a legacy aluminum alloy, AA-7075, and a newer Al-Li alloy, AA-2070. The approach links electrochemical and microstructural characterization of the surface to the microscale corrosion processes. The experimental electrochemical characterization includes optical microscopy, SEM, TEM, XRD, Scanning Kelvin Probe Force Microscopy, Microcell electrochemistry, and zero resistance ammeter measurements. The microstructure characterization techniques include a combination of optical microscopy, SEM, TEM, XRD, and EBSD. Additionally, high throughput screening for corrosion analysis is being developed that incorporates small scale experiments, and the analysis of exposed panels. These descriptions are unified through: a corrosion database; microstructure evolution models; a multi-physics microgalvanic corrosion model; a phase field model; and Bayesian models of pit growth. The validation and verification of the ICME tools uses corrosion pit formation on both salt fog cabinet exposed and outdoor exposed coupons. These tests will provide the input for future demonstrations on manufactured components, and demonstration of corrosion ICME toolset, to link corrosion exposure testing and modeling with design, life prediction, and certification requirements.

9:20 AM  
A Thermo-mechanically Coupled Model to Predict Joint Properties in Friction Stir Scribe Welding of Dissimilar Materials: Varun Gupta1; Piyush Upadhyay1; Xin Sun1; Erin Barker1; Leonard Fifield1; Blair Carlson2; 1Pacific Northwest National Laboratory; 2General Motors
    Joining process simulation is part of the ICME spectrum aiming at computationally linking the joining process parameters to the joint properties. The friction stir welding process is becoming increasingly common as a method to join dissimilar materials and has wide spread applications in several industries, including automotive, aerospace, robotics, shipbuilding and offshore energy production. The solid state nature of the process enables joining materials with significantly different physical properties. The present work focuses on the friction stir joining of fiber reinforced polymer composite to aluminum alloys. For welds in lap configuration, an enhancement to this technique, known as friction stir scribe (FSS), is made by introducing a short hard insert, referred to as cutting-scribe, at the bottom of the tool pin. The cutting-scribe induces deformation in the bottom plate material which leads to the formation of hook-like mechanical interlocks at the interface of the two materials. A thermo-mechanically coupled finite element model is developed to quantitatively capture the morphology of these interlocks formed during the FSS welding process. The identified interface morphology coupled with the predicted temperature field from this process-structure model can be used to estimate the post-weld microstructure and the associated joint strength. The computational model is used to study the effect of different process parameters including tool geometry, welding and rotational speed on the interfacial morphology and the resulting joint mechanical properties.

9:40 AM  
First Principles (DFT) Calculation of Ti3B4 Elastic Constants: Somnaang Rou1; K.S. Ravi Chandran1; 1University of Utah
     Elasticity of strong borides, especially the independent elastic constants that are specific to the crystal structure, are important for the fundamental characterization of their mechanical behavior and physical properties. In this work, the nine-independent elastic constants of the new titanium boride compound, Ti3B4, having the orthorhombic crystal structure is determined rigorously using density functional theory based calculation approach. This was done through the strain energies as determined, for specific deformations, within WIEN2k utilizing full potential linear augmented plane wave (FLAPW) and generalized gradient approximation (GGA). It has been found that the polycrystalline Voigt-Reuss-Hill averages of the independent elastic constants, are quite high (E=492GPa, G=217GPa, B=224GPa, =0.13) placing this boride very close to the well-known titanium diboride (E=570GPa, G=254GPa, B=249GPa, =0.12). The elastic anisotropy of this compound, compared to TiB and TiB2 is comparable, exhibiting low levels of anisotropy. The calculated anisotropy about the {001} plane, however, exhibits notably increased levels of anisotropy due to the directionally dependent bonding of the hexagonal boride chains within the lattice. The same boride chains were found to be responsible for the high modulus, particularly in the [001] direction. Additionally, the charge densities were determined to cause electron accumulation near the boride chains, resulting in strengthening of the B-B chain bonds.

10:00 AM Break