Materials Processing Fundamentals: Solid-state Processing
Sponsored by: TMS Extraction and Processing Division, TMS: Process Technology and Modeling Committee
Program Organizers: Antoine Allanore, Massachusetts Institute of Technology; Jonghyun Lee, Iowa State University; Guillaume Lambotte, Boston Electromet

Thursday 8:30 AM
March 2, 2017
Room: 17B
Location: San Diego Convention Ctr

Session Chair: Jonghyun Lee, Iowa State University; Samuel Wagstaff, Novelis

8:30 AM  
Microstructural and Mechanical Behavior Evolution of Uranium During Thermal-Mechanical Deformation Processing: Daniel Coughlin1; Rodney McCabe1; Kester Clarke2; Jeffrey Scott1; Robert Forsyth1; Donald Brown1; Bjorn Clausen1; David Alexander1; 1Los Alamos National Laboratory; 2Colorado School of Mines
    Processing often involves multiple steps that include rolling, forming, and annealing. We are performing experiments for the development and validation of microstructure based models that predict the evolution of material microstructure and properties during thermo-mechanical processing of depleted uranium. Microstructure characterization, including neutron diffraction and electron backscatter diffraction (EBSD), and mechanical testing are used throughout the processing to evaluate the evolution of the microstructure and mechanical behavior, specifically paying attention to grain size, texture, and hardness. Additionally, digital image correlation is used to collect strain information during forming steps. The data from each processing step using the various techniques is then utilized to validate the model.

8:50 AM  
Gleeble Sintering Simulations of Cryomilled Aluminum AA5083: Frank Kellogg1; Jennifer Sietins2; Brandon McWilliams2; Anit Giri3; Steven Kilczewski4; Kyu Cho2; 1Bowhead Science and Technology; 2US Army Research Laboratory; 3SURVICE Engineering Company; 4Bennett Aerospace
    The Gleeble 1500 can simulate thermo-mechanical processes (welding, rolling, forging, etc.) through heat and strain inputs. Due to its heating capabilities and controllable environment, it can be used to conduct sintering experiments. Through sample design, large thermal gradients can be introduced, creating a temperature range across the sample. These gradients can be used to simulate sintering over a large range of temperatures with one experiment. In this study, cryomilled aluminum AA5083 powder was cold-isostatic pressed at different pressures into rods of different green density values. After pressing, the samples were loaded into the Gleeble and heated to a set temperature of 600oC. Sample temperature was monitored through thermocouples and in situ digital image correlation. To study the effect of sintering and cold pressing parameters, the resulting samples were examined via x-ray computed tomography for porosity distribution, x-ray diffraction for grain size measurements, and scanning electron microscopy for microstructural evolution.

9:10 AM  
Phase Transformation and Precipitation Modeling of Hypereutectic Al-Mn Alloy during Solidification: Jiwon Park1; Jae-Gil Jung1; Chang-Seok Oh1; 1Korea Institute of Materials Science
    A computational model based on the phase field approach is used to simulate Al6Mn precipitation during solidification of hypereutectic Al-Mn alloy. Al6Mn precipitate shows various types of morphology depending on the alloy composition and solidification rate, such as needle-like, cuboid, or hollow hopper-shaped; these exhibit distinct facet planes. In this study, formation of Al6Mn precipitate out of liquid matrix and subsequent eutectic solidification is simulated in perspective of anisotropy. In the simulation Al6Mn is presumed to be orthorhombic and the formation of quasicrystal is not taken into account, as the solidification rate is slow enough. The computed result is validated through in comparison with micrographs of as-cast Al-Mn ingot showing acceptable agreement in meso-scale level. The primary shape of the precipitate is hollow hopper, and its orientation relationship with α-Al is examined in TEM analysis

9:30 AM  
Experimental Study and Modeling of the Stress Field in Macroscopic Creep Feed Grinding Process: Zhenguo Nie1; Gang Wang1; Yiming (Kevin) Rong1; 1Tsinghua University
    Grinding-introduced residual stress is one of the key indicators of surface integrity. The modeling of macroscopic grinding process is reasonly complicated due to combined actions of multi-grains. A modeling method of stress field of macroscopic creep feed grinding process was proposed to predict the residual stress. When there is no phase transformation in grinding, a stress equivalence hypothesis was proposed to map the stress field between micro abrasive grain and macro grinding process. When there is phase transformation in grinding, a transformation-stress coupled model was established to describe the stress field. Both the two models were fully validated by the measured value of the residual stress distribution.

9:50 AM Break

10:10 AM  
Mathematical Modelling of Residual Stresses in End Milling: Sunday Ojolo1; 1University of Lagos
     In this work, mathematical models were developed to simulate the temperature distribution in two flute and four flute end mills during slotting operation. The Differential equation obtained by modelling the physics of the machining process, subject to appropriate boundary conditions based on energy interactions at the tool boundary, was solved by finite difference method implemented in MATLABTM. Descriptive geometric equations were also developed to define the boundary of the tool. Temperature distribution results were obtained typical of a High Speed Steel tool machining a mild steel workpiece subject to variations in machining parameters such as Tool diameter of 25mm, depth of cut of 2mm, Tool Feed of 0.17mm/tooth, Tool Speed of 860 rpm, Tool material conductivity of 40W/m.K, Tool specific heat capacity of 475J/kg.K, Tool density of 8150kg/m3, Specific energy of Tool-workpiece material pair of 4 W.s/mm3.

10:30 AM  Cancelled
Study on Microstructure of Ferritic Stainless Steel Joints Using Electrically Assisted Brazing: Viet Tien Luu1; Yong-Ha Jeong1; Ju-Ri Kim1; Gi Dong Park1; Sung-Tae Hong1; Hyun-Min Sung2; Heung Nam Han2; Kwang-Sun Yu3; Seok-Hyun Kim3; 1University of Ulsan; 2Seoul National University; 3Se Jong Industrial Co. Ltd.
    The electrically assisted (EA) brazing of ferritic stainless steels using nickel-based filler is experimentally investigated. The temperature of a lap joint is rapidly and locally increased to a brazing temperature by a continuous electric current and then is held nearly constant for a few seconds by a pulsed electric current. The result of scanning electron microscopy (SEM) of cross-sections of EA-brazed joint indicates that a sound brazing joint is fabricated. The interfacial reaction between ferritic stainless steels and nickel filler metal in EA brazed joint is investigated by energy dispersive spectroscopy (EDS). The results suggest that the diffusion phenomenon is significantly enhanced in EA brazing in comparison with conventional induction heated brazing with a similar temperature profile. It is speculated that the enhanced diffusion during EA brazing is related with an effect of electric current on the mobility of metal atoms, distinct from well-known joule heating.

10:50 AM  Cancelled
Preliminary Investigations into the Nano/Microstructural Design of Nanocomposites for Combustion Synthesis Processing: Mehul Chauhan1; Prathmesh Modi1; Vanessa Bundy1; K. Morsi1; 1San Diego State University
    The presentation describes a new nano and microstructural design that allows the production of high-density nanocomposites via combustion synthesis without the need for externally applied pressure. Preliminary processing and characterization experimental results are presented for Ni3Al-CNT intermetallic composites, showing effects on product density and homogeneity.

11:10 AM  
Machining Behaviour of Biodegradable Polymer: Force, Damage and Temperature Analysis: Mridusmita Roy Choudhury1; Kishore Debnath1; 1National Institute of Technology Meghalaya
    Biodegradable polymers are widely used for the development of numerous engineering products due to their superior multifunctional properties such as, low density, biodegradability, biocompatibility, and fairly good mechanical properties. In recent years, these materials are being used for making of a wide variety of sophisticated medical devices such as, orthopaedic fixation devices, ligature clips, tissue staples, and stents. In the present research endeavour, the drilling behaviour of biodegradable polymer namely; polylactic acid (PLA) has been experimentally investigated. The drilling of PLA was performed at different levels of feed (8, 16, and 24 mm/min.) and speed (700, 1400 and 2100 RPM) using different drill bits namely; twist drill bit, multifaceted drill bit, and dagger drill bit. The influence of the input parameters on the drilling induced force and damage has been experimentally investigated. The temperature distribution during the drilling of biodegradable polymer has also been investigated to emphasize the drilling mechanism.

11:30 AM  
Evaluation Feature of Nano Grain Growth of TiO2 Thin Film via Sol- gel Route: Habibollah Aminirastabi1; Z.Z Weng1; Z.X Xiong1; G Ji1; H Xue1; 1Xiamen University
    TiO2 films were successfully coated via a spin coating sol–gel route, using tetrabutyl titanate as main raw reagents. One batch of samples was sintered at different temperatures, from 300⁰C to 800⁰C, for 2 hours, while another ones of them were treated at 700 ⁰C for different soaking time (1 to 600 minutes). The phase compositions of the films were identified with X-ray diffraction (XRD). The microstructure of the coating were observed by a scanning electron microscope (SEM). Experimental results indicated that well-developed crystallinity and good morphology of TiO2 could be synthesized above 500 C for 2 h. The crystallinity and morphology of grains in films were affected by the reaction temperature and time. However, image analysis shows that sintering temperature had a great impact on the crystallinity and particles size of the samples above 700 C. Kinetic exponents of grain growth were also obtained with image processing software.