Fundamental Aspects and Modeling Powder Metal Synthesis and Processing: Powder Atomization and Synthesis
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee
Program Organizers: Paul Prichard, Kennametal; Eugene Olevsky, San Diego State University; Iver Anderson, Ames Laboratory

Monday 2:00 PM
February 27, 2017
Room: 16A
Location: San Diego Convention Ctr

Session Chair: Iver Anderson, Ames Laboratory - DOE

2:00 PM  Invited
Fundamental Parameters for Control of Two-Fluid Close-Coupled Gas Atomization: Process Observations and Modeling with Correlations to Metal Powder Yields: Iver Anderson1; Emma White1; Jonathan Regele2; Vince McDonell3; David Byrd1; Ross Anderson1; 1Ames Laboratory; 2Iowa State University; 3University California-Irvine
    Advances in fundamental understanding of close-coupled gas atomization, the preferred large-scale industrial technology for synthesis of precision metal and alloy powders, is required to open up a new era for advanced powder and spray processing. Advanced manufacturing applications that demand these advances include additive manufacturing, metal injection molding, thermal spray deposition, and atomization spray deposition. At the heart of these advances is precise control of the droplet breakup mechanism with extreme uniformity from a melt sheet or ligament source within a highly localized atomization zone, which promotes close control of the energy transfer process that produces the droplet spray. High speed observations of discrete-jet close-coupled gas atomization with open or closed wake gas flow and pre-filming melt pour tubes provided in operando parameters for use in atomization breakup modeling and simulation. Resulting powder size distributions were compared to predicted behavior. Supported by USDOE-EERE-Advanced Manufacturing Office through Ames lab contract DE-AC02-07CH11358.

2:40 PM  
A Study of the Brazing Filler Pastes by Gas Atomized Cu-Fe Powders for Cu/STS Joints: Won-Jung Choi1; Sang-Hun Choi1; Jae-Jin Sim1; Won Ju1; Basit Ali1; Tae-hyuk Lee2; Kyung-Mook Lim1; Bum-Sung Kim1; Taek-Soo Kim1; Kyoung-Tae Park1; 1Korea Institute of Industrial Technology; 2Sheffield University
    There are many applications using the joints between Cu and Fe base alloy such as electrodes, cooling plate, cast mold, chock liner and etc. Commercially, silver contained alloys have been widely selected for brazing the Cu/Fe joints with the various shapes including foil, sheet, powder and paste. In this study, Rapid solidified Cu-Fe powder by gas atomization was applied as the raw materials of high viscosity brazing paste. Although Fe-Cu system is well known immiscible alloy, inside of each powder featured homogeneously microstructure by the gas atomization, that fine Fe grain is well distributed in Cu matrix. From this characteristics, we expected that powder is used as source for the diffusion into its own metal and finally to fabricated one body of dissimilar materials. After brazing using the paste included Fe-Cu powders, it is evaluated that microstructure, ultrasonic scanning and mechanical properties as well as anti-corrosion ability also tested.

3:00 PM  
Fabrication of Ti Powder by Combined Techniques of Cold Crucible and Gas Atomization: Taek-Soo Kim1; Sun-Woo Nam1; Sang-Hyun Lee1; Jae-Jin Sim1; Seok Jun Seo1; Kyung-Mook Lim1; Bum-Sung Kim1; Kyoung-Tae Park1; 1Korea Institute of Industrial Technology
    Recently, metal 3D printing technology have been rapidly developed and spread on the large fields of manufacturing industry. From the development of 3D printing, it has to be developed on the raw materials fabricating techniques. Ti is regarded as importance materials for 3D printing because there are many advantages such as high strength to weight ratio, ductility and biocompatibility. However Ti has strong activity with other crucible metals or ceramics as well as gas elements. So, it's difficult to select the crucible for melting the Ti and its alloy. In this study, we suggested that gas atomization with cold crucible melting for spherical shape of Ti powder which could be applied for raw materials of 3D printing. Capability of Ti atomization is higher than 1kgs and close coupled nozzle is used for guiding the melted Ti. The impurities, morphology, microstructure and mechanical properties of Ti powder are analyzed and discussed.

3:20 PM  
Microstructural Development in Binary Aluminum-Copper Alloy Powders during Gas Atomization: Tian Liu1; Luke Brewer1; 1University of Alabama
    This work studied the microstructure of binary aluminum-copper powders (2-5 wt% Cu) produced by inert gas atomization. Gas atomization is one of the key processing techniques for producing alloy powders used in powder metallurgy production and, more recently, for cold gas dynamic spray deposition. The micro- and nanostructures were studied using SEM, TEM, and precession electron diffraction. These powders all exhibited a cellular solidification structure with the Al2Cu, theta, phase along the cell boundaries. The extent of cell boundary coverage increased with increased copper content. The cell size was quite small, approximately 2 microns, and varied only slightly with copper content. Guinier-Preston zones were not observed in the gas atomized powders even after eighteen months of natural aging. Small Al2Cu precipitates were present inside the cells, but with random crystallographic orientations. Using helium gas, these alloy powders were successfully deposited as high density coatings via the cold spray process.

3:40 PM Break

4:00 PM  
Influence of the Plasma Gas Composition and Power Level on the Processing of Powders by Induction Plasma: Siwen Xue1; Richard Dolbec1; Thomas Kinsey1; 1Tekna Plasma Systems Inc
    The conversion of particles of various morphologies into perfectly spherical powders by induction plasma is a mature process which is attracting sustained interest as a result of the growing demand for high quality powders required by the additive manufacturing processes. We report here a comprehensive study based on modeling experiments that describes the influence of the main processing parameters on the thermodynamic properties of the induction plasma process (also known as the Tekna process). A case study for the processing of a refractory metal will be presented.

4:20 PM  
Mesoscale Modeling of Single Particle Impact Induced Microstructural Evolution during Cold Spray of Aluminum Powders: Sumit Suresh1; Benjamin Bedard1; Tyler Flanagan1; Seok-Woo Lee1; Mark Aindow1; Harold Brody1; Xuemei Wang2; Victor Champagne3; Avinash Dongare1; 1University of Connecticut; 2United Technologies Research Center; 3U.S. Army Research Laboratory
    The cold spray process involves acceleration of metal particles at supersonic velocities on to a metal substrate for applications in coatings, repair and manufacturing technologies. A critical challenge in optimizing the applicability of the cold spray process is the understanding of the deformation behavior during particle impact. Mesoscale simulations are therefore carried out to investigate the microstructural evolution during impact of Al particles with sizes up to tens of microns on to a metal substrate using a newly developed quasi-coarse-grained dynamics (QCGD) method. The QCGD method is based on solving the equations of motion for a chosen set of representative atoms from an atomistic microstructure and retaining their energetics using scaling relationships for the atomic scale interatomic potentials as would be used in MD simulations. The scaling relationships, and the effect of particle size, temperature of the particle and impact velocity on the predicted microstructural evolution will be presented.

4:40 PM  
Algorithmic Prediction of Bulk Properties from Powdered Feedstock Consolidated via Laser-assisted Cold Spray: Aaron Birt1; Diran Apelian1; 1Worcester Polytechnic Institute
    Laser-assisted cold spray (LACS) is a solid state supersonic powder deposition process wherein the powders are deposited onto a region of substrate heated by a laser. The process has high build rates, hard deposits, and is fairly cost-effective due to use of nitrogen as the carrier gas. All of these benefits are derived from a set of extremely complex impact phenomena including high strain, thermal gradients, material jetting, and supersonic gas exchange. As a result, predicting material properties based exclusively on a defined set of system parameters is extraordinarily difficult even for an experienced user. To combat this, research has begun focusing on a set of statistical algorithms that can handle complex, noisy, and limited data. Using data from input powders, substrates, and system parameters, these algorithms will be discussed regarding their ability to predict, with varying degrees of success, key resultant properties of LACS deposits.

5:00 PM  
Formation of Nano-lamellar Structure in Ni-Al High-density Energetic Material by Cryomilling: Minseok Oh1; Byungmin Ahn1; 1Ajou University
    High-density energetic materials are generally utilized in specific military and civil applications where a high ratio of potential chemical energy output is required. Ni-Al material system was known as an energetic material because of its exothermic reaction during formation of intermetallic compound. The reaction initiation temperature can be lowered when Ni and Al form nano-scale interlamellar structure facilitating the reaction so that the exothermic output can be accomplished with less energy input. In the present study, the nano-lamellar structure of Ni-Al was effectively achieved using cryomilling technique minimizing unnecessary oxidations. The microstructural evolution during cryomilling was investigated in details.

5:20 PM  
Microstructural Evolution in Dilute Mg-X Binary Alloys Processed by Mechanical Alloying: Christian Roach1; Kiran Solanki2; Suveen Mathaudhu1; 1UC: Riverside; 2Arizona State University
    Grain size refinement is one of the most commonly used strengthening methods for metals, however, this approach has not been investigated in Mg and its alloys due to the reported suppression of twinning (and thus loss of important plasticity mechanisms). More so, combining the low melting point of Mg-alloys with a nanocrystalline state makes them susceptible to grain growth at low homologous temperatures. In this work we report the microstructural evolution and thermal stability of Mg and Mg-X (Al & Y) alloys at various concentrations of solute after processing by high-energy ball milling. Phase formation and grain size were probed via precision x-ray diffraction and Williamson-Hall analysis. Additionally, mechanical properties and response were investigated via instrumented nano- and micro-indentation testing. These results will help steer processing and synthesis of advanced nanocrystalline Mg-alloys with enhanced mechanical properties and performance.