2017 Technical Division Student Poster Competition: Materials Processing and Manufacturing Division (MPMD) Graduate Students
Sponsored by: TMS Extraction and Processing Division, TMS Functional Materials Division, TMS Light Metals Division, TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division
Program Organizers: TMS Administration

Monday 5:00 PM
February 27, 2017
Room: Hall B1
Location: San Diego Convention Ctr

SPG-25: A Study on the Development of High Efficiency Cooling Channel Fabricated by Explosive Welding Process in the High Pressure Die Casting Mold: Sang Soo Shin1; Chang Yong Choi2; Ki Hyuk Kim3; 1PNU; 2Ohsung Tech; 3Dong Kuk steel
    In this study, commercial steel tool alloy of the cylindrical configuration and commercial copper bush were bonded through explosive welding process. Several types of explosive material were used to investigate its influence on the bonding morphology and interface. Ammonium Nitrate Fuel Oil (ANFO) powders were used as explosive material and the bonding process was carried out as function of clearance gap and flyer thickness. Microstructures of the bonded sections were examined and then compression shearing tests and hardness measurements were carried out on the bonded specimens. Compression-shearing tests results showed that shear and fracture took place in the copper plates not in the joining interface. SEM with EDS results showed that no traces of intermetalics were observed in the interface. Finally, die casting molds bonded with dissimilar metals (SKD61+ Cu) showed low temperature and homogeneous temperature distributions, as a from thermal imaging camera results.

SPG-26: Bulk Metallic Glass Casting: Insights into Critical Cooling Using High-speed IR Monitoring and Fast DSC: Fabian Haag1; Güven Kurtuldu1; Jörg Löffler1; 1ETH Zurich
    Processing of bulk metallic glasses (BMGs) is limited by the temperature interval in which the alloys are in their so-called supercooled liquid range. Frequently, BMGs are characterized by their critical cooling rate. Although this value gives information about the processability of glass-former melts, it does not represent the actual cooling behavior when (complex) molds are filled by the molten alloy. We have designed a novel setup for quantitative recording the cooling upon casting using a high-speed infrared camera. Here, we want to introduce the method, show its prerequisites, and discuss its potential for detailed analyses of mold casting. Using low-Tg Au-based BMGs, we plot local cooling curves for fully amorphous, partly amorphous and crystallized regions of cast parts. The proposed technique allows for investigating individual cooling history by fast DSC (FDSC). We find accurate correlation with time-temperature-transformation diagrams, continuous-cooling-transformation diagrams and quantitative agreement between the IR results and FDSC.

SPG-27: Design of New Ni-Based Superalloys for Electron Beam Additive Manufacturing Process: Curtis Frederick1; Ryan Dehoff2; Michael Kirka2; Edwin Schwalbach3; Michael Haines1; Austin Staub3; Suresh Babu1; 1University of Tennessee, Knoxville; 2Oak Ridge National Laboratory; 3Air Force Research Laboratory
    Moving grain structure from equiaxed to directionally solidified and finally to single crystal is known to greatly improved the mechanical properties of traditionally produced Ni-based superalloys. Determining the alloying rules for highly oriented grains in electron beam additive manufacturing is therefore of great importance if parts made via this process are to be competitive in these markets. A model was produced based on welding research to include the effect of composition on the columnar to equiaxed transition. Two compositions were identified and powder was produced by Oerlikon. Builds made with an Arcam A2 using this powder with compositions derived by the model will be characterized and presented as validation.

SPG-28: Dynamic Transformation of Austenite to Ferrite during Rolling above the Ae3 Temperature: Samuel Rodrigues1; Clodualdo Aranas Jr.1; John Jonas1; 1McGill University
    When austenite is deformed by rolling above the Ae3 temperature, it transforms dynamically into Widmanstatten ferrite by a displacive mechanism. On removal of the load, it slowly retransforms back into the more stable austenite by diffusional processes. This influences the rolling load which does not increase with decreasing temperature as rapidly as expected during rolling. Such ferrite forms when the driving force for dynamic transformation overcomes the total energy obstacle preventing its formation. The latter consists of the free energy difference between the phases as well as the lattice dilatation work and shear accommodation work. Nucleation and growth of the softer ferrite reduce the rolling load and modify the microstructure. Furthermore, under dynamic conditions, the ferrite phase field, in a specific steel phase diagram, extends all the way from room to very high temperatures.

SPG-29: Effect of Beam Oscillation on Electron Beam Welding of Ti-6Al-4V Alloy: Jyotirmaya Kar1; Sanat Kumar Roy1; Gour Gopal Roy1; 1IIT Kharagpur
    Butt joints of the Ti-6Al-4V alloy were prepared by electron beam welding using both oscillating and non-oscillating beam. While preparing the joints, heat input was kept constant, so that the effect of beam oscillation on the weldment quality could be investigated. The prepared joints were subjected to detailed microstructural investigation and phase quantification. Residual stress distributions and fatigue life of the prepared joints were evaluated. Other mechanical tests include microhardness measurements, tensile and Charpy impact tests in accordance with the ASTM standards. Microstructural analysis demonstrated that the joints made using beam oscillation possessed smoother weld bead surface with narrower HAZ and fusion zones. It is further observed that for certain optimized parameters of beam oscillation, ductility and notch toughness of the weldment are enhanced significantly. Residual stress and fatigue life of the joints are also found to be influenced by beam oscillation.

SPG-30: Ex-situ and In-situ TEM Investigation of Texture Dependent Strain Rate Sensitivity of Bauschinger Effect in Ultrafine-grained Al Films: Ehsan Izadi1; Jagannathan Rajagopalan1; 1Arizona State University
    Several studies have investigated the texture dependent strain rate sensitivity of flow stress in nanocrystalline and ultrafine-grained metals. However, there is limited understanding of how sample texture affects their deformation behavior during unloading. To address this issue, we performed load-unload experiments on two sets of freestanding ultrafine-grained Al films of similar thickness (~200 nm) and mean grain size (~250 nm) but with very different textures - one with (110) out-of-plane texture (bicrystalline) and another with no preferred texture (non-textured) - at strain rates between 〖10〗^(-5)/s to 〖10〗^(-2)/s. We measured the early Bauschinger effect (BE) to quantify the deviation from linear elastic behavior during unloading. Our results indicate that, in contrast to the bicrystalline film, the non-textured film shows substantially higher BE and higher strain rate sensitivity of BE. In situ TEM experiments with automated crystal orientation mapping are used to interpret these observations and uncover the underlying mechanisms.

SPG-31: Grain Size Effect on the Deformation of Nanograined Metallic Multilayers: Sixie Huang1; Caizhi Zhou1; 1Missouri University of Science and Technology
    Plastic deformation of nanograined Cu/Nb multilayers was studied by molecular dynamics simulations. Under loading, dislocations initially nucleate from the grain boundary triple junctions, rather than the interface. The extended full dislocations are frequently observed in larger grains, while partial dislocations generating stacking faults are prevalent in smaller grains. The dislocation-mediated processes, such as dislocation nucleation and gliding, are the dominating deformation mechanism for all grain sizes. The layer thickness dependent flow stress can be explained by confined layer plasticity model. Moreover, an inverse grain size effect on the flow stress is observed when the layer thickness approaches 5.0 nm.

SPG-32: In-situ Observation of Diffusion Behavior and Microstructural Evolution on Interfaces in Al/Cu Bimetal: Fei Cao1; Fenfen Yang2; Huijun Kang2; Zongning Chen2; Tiqiao Xiao3; Tongmin Wang2; 1Dalian University of Technology ; 2Dalian University of Technology; 3Shanghai Institute of Applied Physics, Chinese Academy of Sciences
    Time-resolved synchrotron X-ray radiography was used to in situ study the diffusion behavior and microstructural evolution of Al/Cu bimetal interface. The interface diffusion, dendritic/eutectic growth and the formation of intermetallic compounds around the Al/Cu bimetal interface were quantitatively analyzed. During the isothermal diffusion process, the concentration variations of Al and Cu around the interface were quantitatively analyzed through the extraction of gray level from sequenced X-ray images. During the solidification of interface zone, the growth sequence of α-Al dendrites, Al2Cu and eutectic structure were mainly dominated by the variation of Cu concentration and thermal field according to the temperature of the liquidus line of the equilibrium phase diagram. Finally, four transition zones around the interface were identified to be I (α-Al), II (Al+Al2Cu), III (Al2Cu) and IV (AlCu, Al2Cu3 and Al4Cu9), respectively.

SPG-33: Iron's Role in the Refinement of Aluminum-silicon by Trace Amounts of Strontium: Tara Power1; Sumanth Shankar1; Jeffrey Hoyt1; 1McMaster University
    Aluminum-Silicon (Al-Si) alloys have been vastly modified through minute addition of Strontium, transforming the morphology from coarse and plate-like to fine and fibrous, which contains an important improvement for use in industry. Though, the mechanisms involved still elude scientists today. In typical cast Al-Si alloys, there is an Iron phase present which is a favourable site for Silicon nucleation. Through Density functional theory, Ab-Initio Molecular Dynamics and reverse Monte Carlo simulations, the implications of this Iron phase in Al-Si was tested, with and without the addition of Strontium. These results were then compared directly to diffraction experimental results. Through an understanding of the nature of Iron’s role in this modification, the reason for this change in morphology can be deciphered. Such knowledge is useful for refinement of mechanical properties for use in industry.

SPG-34: Mechanical and Microstructural Evaluation of Ultra High Speed FSW of Aluminum Alloys: Jingyi Zhang1; Piyush Upadhyay2; Yuri Hovanski3; David Field1; 1Washington State University; 2Pacific Northwest National Laboratory; 3Brigham Young University
    Ultra-high speed friction stir welding on aluminum alloy tailor blanks enables high volume production rate. This study evaluates the effect of high process speed on the mechanical properties, microstructural features and the material flow pattern in and around the joint made on highs strength aluminum alloys. Micro-hardness profile revealed less intense and smaller softened HAZs are associated with welds made under higher joining speed. SEM and EBSD technique are employed to analyze the flow pattern inside the stirring zones. The flow patterns in stirring zones are found to have a unique trend with higher speed. The severe inhomogeneity across the weld region also introduce uneven corrosion resistance properties over various regions.

SPG-35: Non Equilibrium Thermodynamics of Quench and Partition Steels: Amit Behera1; 1Northwestern University
    Quench and Partitioning (Q&P) is a novel concept that promises to take the third generation of advanced high strength steels (AHSS) to better combinations of strength and ductility while reducing the overall manufacturing costs. Thermodynamics based genomic design approach supported by advanced microstructural characterization techniques would help design optimized processing routes and new steel compositions without the need for prolonged experimental studies. The current work puts effort to understand and model non-equilibrium thermodynamics behind the different phase transformations occurring during the Q&P cycle. Experimental measurements are used to quantify stored energy for displacive transformations. Models based on the thermodynamic and kinetic aspects of these transformations are developed and simultaneously used to design optimized processing cycles and new alloy compositions. The thermodynamic and kinetic simulations with use of commercially available software such as ThermoCalc, DICTRA are calibrated and compared to highly accurate experimental measurements using electron microscopy and 3-Dimensional Atom Probe.

SPG-36: Preparation of TiB2 by Mechanochemical Reaction between Al, B2O3 and TiO2: Petra Hanusova1; 1Brno University of Technology, Faculty of Mechanical Engineering
    One possible route for producing the fine and homogenous distribution of hard particles in composite microstructure is the mechanochemical processing in which high - energy ball milling promotes. This research is based on the production TiB2 phase using mechanochemical processing. For this purpose a mixture of aluminium, boron (III) oxide and titanium oxide powders was subjected to high energy ball milling. The structural evaluation of powder particlesafter different milling times was conducted by X - ray diffractometry (XRD) and scanning electron microscopy (SEM).

SPG-37: Seed Layer Mediated Crystallization of Amorphous Structural Thin Films to Yield Gradient Microstructures: Rohit Sarkar1; Jagannathan Rajagopalan1; 1Arizona State University
    Gradient microstructures in nanocrystalline (nc) films can impart unprecedented properties in these materials. However, conventional techniques to synthesize nc thin films cannot achieve comprehensive control over their grain size and distribution. Here, we introduce a novel technique to obtain gradient microstructures in intermetallic films by controlling their crystallization from an amorphous phase. Magnetron co-sputtering was employed to deposit amorphous TiAl and TiNi thin films. Crystalline seeds of Ti and Cr were encapsulated between these amorphous layers to act as heterogeneous nucleation sites. The spacing of these seed layers along the thickness of the films (λ) was systematically varied to control the grain aspect ratios. The films were subsequently annealed in vacuum to induce crystallization. Transmission electron microscopy of the films revealed that precisely controlled gradient microstructures were obtained by systematically varying λ. Additionally, changing the seed element caused specific phases to preferentially stabilize.

SPG-38: The Effects of Transition Metal Element Addition on the Temporal Evolution and Microstructural Characteristics of Nickel-based Superalloys: Rasim Eris1; M. Vedat Akdeniz1; Amdulla O. Mekhrabov1; 1Middle East Technical University
    Transition metal element addition and determination of optimum heat treatment procedures are two common ways to improve phase stability and mechanical properties of Nickel-based superalloys. Thus, in the current study, the effects of transition metal X elements (i.e. X= Ti, Nb, Hf, Co) on the ordering characteristics, solidification structures and phase stability of Ni80Al15X5 alloy systems will be presented and compared with each other and binary Ni80Al20 alloy. Temporal evolution of binary and ternary systems will be examined by applying different heat treatment procedures including distinct aging times. Mechanical tests including hardness measurements will be done for each as cast and heat treated samples and the results will be discussed in terms of microstructural characteristics determined by scanning electron microscope (SEM). Furthermore, by applying phase analysis (XRD), thermal analysis (DSC) and magnetic analysis (VSM), all experimental results will be supported.