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Wednesday Sessions
9:30 a.m. - 10:45 a.m.

PowderMet          AMPM          Tungsten          Special Interest

PowderMet Abstracts



SESSION P19   Novel Processing


002 - Microstructural Evolution Simulation for Property Prediction in Cold Spray Processing
Danielle Cote, Worcester Polytechnic Institute

The cold spray process is a dynamic powder consolidation technique capable of producing materials with high strength and toughness through an extremely versatile processing system.  In this solid state additive manufacturing process, the consolidated material and mechanical properties are directly dependent on the powder properties. To account for this relationship, a through-process model was developed as a predictive tool to follow the microstructural evolution of the cold spray process – from as-received powder to post processing consolidated material. The significance of the feedstock powder properties becomes evident in this work and will be discussed in terms of kinetic, thermodynamic, and solidification predictive simulations and experimental characterization. The final model predicts material and mechanical properties of the consolidated material as a function of feedstock powder and process parameters. Examples of aluminum, steel, and refractory powders are demonstrated.

079 - Research into Near Shape Processing of Magnesium and Magnesium Alloy Powders
Steven Johnson, Central Connecticut State University

Near shape forming of magnesium (Mg) alloys offers a significant opportunity for light weighting of structural materials. Work has been performed using conventional press and sinter (P + S) near shape processing of prealloyed AZ91D and pure Mg powders. Results indicate these powders are reasonably compressible achieving green densities of 88 to 98% Th with limited cracking. However sintering of these powder compacts appears to require both solid state and liquid phase mass transport, with limited increase in density above green densities occurring. Results of this work are presented as density, hardness, microstructure, and phase development of the P + S processed AZ91D and Mg powders. Additionally x-ray diffraction, x-ray fluorescence, and thermal analysis investigations into the affect oxygen has on sintering are presented. Results of this work are intended to progress near shape processing of Mg base powder materials for potential structural applications.

016 - Compatibility of CIM Feedstock With 3D Printed Single-Use Polymer Molds
Kyriakos Didilis, AddiFab

The invention of single-use 3D-printed polymer molds potentially enables the design freedom and high pace of additive manufacturing without compromising the wide material selection of injection molding. For ceramic injection molding (CIM) feedstocks, the processing parameters are largely determined by the binder system employed. Several types of binder systems exist, requiring different treatments during the production process. The exact composition of a specific feedstock is often proprietary, as many CIM part providers produce their own feedstocks in-house. This paper documents the process performance of 3D-printed polymer molds with a ceramic injection molding feedstock in terms of finished part integrity, dimensions and surface finish. 


SESSION P20   Mechanical Properties—Ferrous Materials


051 - Fatigue Performance of a Low Alloy Sinter-Hardened Steel
Ian Donaldson, FAPMI, GKN Sinter Metals

Automotive customers are quickly moving to model-based decision making in the design phase which is reducing the testing of components.  The formalized application of modeling is done to support system requirements, design, analysis, verification and validation activities beginning in the conceptual design phase and continuing throughout development and later life cycle phases.  The drivers are cost, early detection of defects or design issues and timing (reduced design cycle time).  This requires significant mechanical property data of materials.  While static properties of PM materials exist, fatigue data is much more limited which may exclude PM as a potential choice at the design stage.  This is motivation to develop comprehensive fatigue properties at different densities and R ratios. This paper presents characterization and fatigue properties in both un-notched and notched conditions of a FL-4205 based material modified for sinter-hardening.

229 - Finite Element Evaluation the Stress Intensity Factors for Internal Cracks Within a Powder Compact Under Internal Pressure from Entrapped Air
Joseph Wright, Drexel University

Interstitial air in powder compacts can become entrapped when the speed of compaction is high and the permeability of the powder compact is low (e.g. fine powders). Under such conditions the entrapped air is pressurized especially when the density of the compact is pushed to very high values.  For green compacts with low strength this condition tends to produce internal defects - cracks.  In this work we evaluate the stress intensity factor for such cracks under internal pressure for different location along the height of the compact using finite element analysis. The results show that cracks closer to the surface are tend to exhibit a higher stress intensity factor for the same level of internal pressure.   This work is relevant to the prediction of defect formation in compaction. 

102 - Effect of Phosphorus and Carbon on Microstructure and Properties of High Manganese Non-Magnetic Steel
Chongxi Bao, NBTM New Materials Group Co. Ltd

Sintered high manganese non-magnetic steel parts were prepared by pressing-sintering method. The effect of Fe3P and carbon content on microstructure and properties of high manganese non-magnetic steel was studied. Properties of high manganese steel containing Fe3P and copper were compared. The results show that the non-magnetic high manganese steel with uniform structure can be prepared by adding Fe3P to the high manganese steel powders. In high manganese steel, the addition of Fe3P is less than 2%, and the non-magnetic property of high manganese steel is better. In the high manganese steel containing 2% Fe3P, the carbon content after sintering is less than 0.93%, the precipitates between grains are less,the non-magnetic property of high manganese steel is better. The mechanical properties of high manganese steel containing 2% Fe3P are higher than those of high manganese steel containing 7.52% copper, and the sintering temperature is lower, so it has lower cost advantages.


SESSION P21   Lightweight Materials 


061-R Lightweighting Material and Process Options for Automotive Applications—Focus on PM Aluminum
Chaman Lall , MPP

Mobility vehicles powered by hydrocarbon fuels are subject to regulation by Federal emission standards that are aimed to reduce greenhouse gases. Because of the high number of automotive vehicles in use globally, they present the greatest threat to the environment. The automotive industry has developed strategies to improve fuel efficiency- one of those being the reduction of vehicular mass. One approach is the utilization of low-density materials such as the alloys of Al, Mg and Ti. This presentation aims to provide an overview of light weighting options using these materials, with a specific focus on the powder metallurgy (PM) technology as applied to the processing of aluminum alloys.  An new alloy developed presents an opportunity to reduce mass by 50%; this alloy has a yield strength of about 300 MPa, and a tensile elongation of about 2%.  The technical and economic feasibility of various paths to vehicular mass reduction will be reviewed.

206 - Powder Consolidation of a High Temperature Aluminum Alloy
Stuart M. Shirley, Colorado School of Mines

An aluminum alloy has been produced via rapid solidification and shown promising high temperature mechanical properties.  High temperature strength stems from the metastable icosahedral precipitates formed during the rapid solidification process.  Understanding the thermal stability of the metastable precipitates defines the processing window for consolidation. Differential scanning calorimetry experiments were conducted in conjunction with x-ray diffraction to characterize the phase evolution of the icosahedral precipitates.

187 - Recent Developments and Trends in Aluminum Powder Metallurgy
Ian Donaldson, FAPMI, GKN Sinter Metals

The automotive industry has been affected by several factors: global government emissions and fuel economy regulations, increasing global warming concerns and increasing car weight caused by continual addition of car features. To address these factors, automotive companies have focused on lightweighting through new technologies and materials to reduce overall vehicle weight.  For example, a 10% reduction in the mass of a vehicle can yield approximately 6-8% increase in fuel economy.  Consumer preferences limit the downsizing possibilities available to automakers, while safety and performance standards minimizes the ability to reduce weight further with conventional materials.  One area that the lightweighting trend has spurred research and development is in powder metal (PM) aluminum.  This paper provides a perspective on the recent developments, current research and trends driving future research in the area of PM aluminum.


AMPM Technical Abstracts



SESSION A25   Sinter Based AM I


241 - Optimization of Water Atomized 17-4 Stainless Steel for Binder Jetting
Edel Arrieta, University of Texas

In recent years, there has been an upsurge in the Additive Manufacturing (AM) process of Binder Jetting for production in different industries (e.g. automotive) as it provides rapid production and development cycles, low material waste, and a freedom of design that is unachievable with traditional manufacturing methods. A significant limitation of all AM processes’ is the cost of production parts, thus there is considerable interest in more economic powders that will greatly reduce production costs while maintaining part performance. One such powder production method already used in high volume production is water atomization. Here, we evaluate water atomized 17-4 Stainless Steel produced specifically for use in Binder Jetting with the goal of manufacturing parts with sintered density comparable to that achieved with gas atomized powders.

064 - Comparison of Binder Jet and Laser Powder Bed Fusion for Co-Cr Alloys 
Zhuqing Wang, Kennametal Inc.

The properties of the Co-Cr alloys comprising the Stellite TM alloy family can be tailored to a variety of wear applications and aggressive environments. These versatile alloys can develop significantly different properties as a result of processing such as casting, PTA, HVOF, P/M sinter or P/M HIP.  Additive manufacturing processes such as laser powder bed fusion and binder jetting have a significant influence on the microstructure, mechanical properties and wear properties.  The comparison of the microstructures between binder jet processed and laser powder bed fusion materials develop a different carbide distribution and grain size of the same Stellite TM composition.  This presentation will discuss the different capabilities of binder jetting and laser powder bed to make complex geometries and the effect of processing on key properties of Stellite TM Alloys.

188 - Powder Casting: Producing Bulk Metal Components from Powder without Compaction
James Paramore, U.S. Army Research Laboratory

Many non-beam additive manufacturing (AM) processes can be used to create metal green parts for subsequent sintering. However, the green parts often have very low relative densities, complicating sintering. For example, extrusion-based AM processes have been adapted to produce green parts using a polymer binder. However, achieving suitable mechanical and rheological properties of the feedstock often requires metal powder fractions of 50 vol% or less. Additionally, unless relatively expensive powders with excellent flowability and packing characteristics are used, binder jetting also produces parts with poor green densities. In this talk, a process called “Powder Casting” will be discussed. This process was originally developed to produce nearly fully dense metal components from loose powder by using hydrogen-assisted sintering to significantly improve densification. Results from different alloy systems and the incorporation of this method into non-beam AM processes to improve densification and, therefore, mechanical properties will be presented.


SESSION A26   Laser Based Refractory Metals


017 - Development of Novel Spherical Multinary Alloy Powders Containing Tantalum and Niobium for Optimization of Intrinsic Material Properties in AM
Melanie Stenzel, TANIOBIS

The high degree of freedom for geometric designs opened by additive processes, is often seen as a main driver for improvement of components but design optimization alone is not enough to achieve highest component performance. Intrinsic material properties also play a vital role to fit parameters to specific requirements of applications. This is especially relevant for applications, in which inappropriate material properties may cause fatal failure. The present paper gives an overview on the development and optimization of refractory metal-based spherical multinary alloy powders with variable composition for biomedical applications. It will be shown how alloy powders based on titanium, tantalum and niobium (Ti/Nb/Ta) applied in laser powder bed fusion (L-PBF) can offer improved biocompatibility and optimized mechanical values compared to conventionally applied implant materials. It will be further shown how those findings can be transferred to the development of multinary and high entropy alloys. 

084-R - Investigations on Laser Powder Bed Fusion of Tungsten Alloys
Nabil Gdoura, Bayerische Metallerke GmbH

Laser powder bed fusion (L-PBF) offers significant potentialities for the design of complex part geometries. Due to the specific combination of properties, tungsten and tungsten heavy alloys are used for special applications such as X-ray and g-radiation shielding, balancing weights, collimators and molds, where complex geometries can be required for optimum performance. L-PBF of tungsten alloys such as W-Ni-Fe is challenging due to the high thermal conductivity, high viscosity of the liquid phase, the high melting point and sensitivity to thermal cracking. The effect of L-PBF processing parameters on the material microstructure of tungsten alloys has therefore been studied for different powder compositions, applying substrate pre-heating temperatures up to 800°C. Furthermore, the impact of thermal post-treatment has been investigated, leading to a microstructure close to conventionally sintered material. Fully crack-free samples have been generated from all powders, but residual pores can still be detected.

221 - Dynamic Metallic Structural Design Enabled via Additive Manufacturing
Vanshika Singh, University of Tennessee, Knoxville

The highest contributor for forced outages in coal-biomass-fired power plants is early creep failure which is 23.4%. Two of the major causes for early creep failure are ash deposition on the heat exchanger tube surface and the overheating of the tube walls due to high fluid temperature flowing through the tube. To address the ash deposition issue, an asymmetric tube design in confluence with parametric shape optimization has been proposed. This design could be manufactured at a higher rate of production with lesser cost via Powder-Bed Fusion methods for Industrial application. Further, to prevent the overheating of the tube, a dynamic cooling channel is proposed which can be achieved via Powder Bed Fusion Method and Ultrasonic Additive Manufacturing. To create the dynamic cooling channels, it is proposed to create a living-like structure that can change its shape or size significantly when subjected to external environmental change without using an external monitoring system, sensors, actuators, special materials like Shape Memory Alloy, et cetera. For this, Origami-based structures and complaint mechanisms will be leveraged to design the living-like structure, while topology optimization will be leveraged to architect the material to increase the elastic compression in the localized regions. Additive Manufacturing methods like Powder Bed Fusion methods as well as Ultrasonic Additive Manufacturing could be used to manufacture the engineered structure and metamaterial. This study opens up the path to study living-like structures in the structural components section and could be leveraged in designing efficient systems like heat exchangers, achieving desired clearance in the high-pressure turbine blade in aircraft engines as well as gas turbine engines, et cetera.


SESSION A27   Process Parameter Effects


012-R - Effect of Atomization Method and Post-Processing Treatments on the Microstructure and Mechanical Properties of Ti-6Al-4V Alloys Manufactured via Laser Powder Bed Fusion
Leandro Feitosa, Sandvik Machining Solutions AB 

Due to the rapid development of AM technologies, special attention is necessary towards reducing processing defects and achieving dense and homogenous materials. In this work, the assessment of Ti-6Al-4V powders fabricated via two of the mostly developed atomization processes, advanced plasma atomization (APA) process, which uses plasma torches to melt and atomize the metal wire feedstock, and electrode induction melting gas atomization (EIGA) is thoroughly carried out. Following production of parts by laser powder bed fusion (LPB-F) and post-processing treatments, which includes stress relief and hot isostatic pressing (HIP) treatments, the resultant mechanical properties at room temperature are reviewed. Microscopy study aimed to detect and discuss the level of microstructural damage and texture and their influence on the performance of pre and post heat-treated parts to obtain optimal parameters to achieve superior properties. A comparison is made between the effect of these stages and traditionally cast and HIPed Ti-6Al-4V alloys.

091 - Effect of Energy Concentration on Properties of Additive Manufactured Ti-6Al-4V via SLM
Farhana Mohd Foudzi, Universiti Kebangsaan Malaysia

High performance of final parts in any processes is greatly influence by the processing parameters. In Selective Laser Melting (SLM), the main parameters are laser power (W), scanning speed (mm/s), layer height (mm) and hatching distance (mm). These parameters sum the energy concentration (J) of a printing process. Nine sets of parameters (P1 – P9) were employed to produce Ti-6Al-4V solid cubic specimens (1 cm3). Surface roughness of 5-20 µm was measured for all specimens. For microhardness, it was found that P2, P6 and P4 specimens gave the lowest (321HV), average (352HV) and highest (389HV) microhardness. The microhardness may be influenced by the energy concentration where the lowest is given by P2 with 69.44 J, followed by P6 (81.85 J) and P4 (98.50 J). Therefore, as the energy concentration increases, so does the microhardness. However, too high energy concentration may lead to excessive burning of the specimens due to high laser power. This is proven by the P9 specimen which was printed at 325 W laser power and 800 mm/s scanning speed. Therefore, too high laser power at very low scanning speed leads to coarsest surface of specimen. Meanwhile, for microstructure analysis, higher microhardness specimen resulted to more β phase compared to α phase. It was observed that P4 specimen has more martensite phase which denoted as thin needle-form compared to P2 specimen. Overall, the influence of processing parameters of SLM on additive manufactured Ti-6Al-4V in terms of surface roughness, microhardness and microstructure was successfully conducted.

167 - Determining the Effect of Layer Thickness on Mechanical Properties of Al-Si10-Mg Produced by Laser Powder Bed Fusion
James Sears, AMAERO Inc

AlSi10Mg is the most common Aluminum alloy in use today in Additive Manufacturing.  Laser Powder Bed Fusion (LPBF) is the primary Additive Manufacturing technique that uses AlSi10Mg as feed stock. With the availability of higher power lasers, thicker build layers are being used especially for AlSi10Mg. This paper reports on the effects of increasing layer thickness has on the mechanical properties AlSi10Mg produced by LPBF.  Microstructural response (especially pore formation) and the resultant mechanical properties are reported.  This information is important when combining various layer thicknesses (e.g., 30, 60 and 90 micron layers) for increasing productivity in LPBF while maintaining part quality.


Tungsten Abstracts



SESSION T09   Tungsten Properties


182-R - Wear Phenomena in Different Cemented Carbides During Rotary-Percussive Drilling in Reinforced Concrete
Steven Moseley, Hilti AG

Rotary-percussive drilling through steel reinforced concrete not only subjects cemented tungsten carbide drill bits to intensive abrasive wear but additionally induces significant microstructural changes in the near-surface regions. These include micro-, meso- and macroscopic cracking; comminution of the WC; delamination of WC-binder interfaces; binder depletion and pore formation; partial WC dissolution and rearrangement; surface decarburization; and the creation of secondary phases within the binder.

In this study, the wear phenomena in cemented carbide drill bits with different WC grain sizes (fine to extra coarse), binder contents (6-12 weight %) and binder types (Co, Co-Ni and Ni) have been documented, analyzed and quantified. Noticeable differences between the various grades are evident. 

A wide range of experimental variables have been investigated covering the large proportion of real-world cases encountered in the application of these drill bits on the construction site. This paper presents a broad overview highlighting how material choice influences wear. 

192 - Plastic Behavior and the Structure of Dislocations in Single Crystal Tungsten
Brady Butler, DEVCOM Army Research Laboratory

The deformation behavior of tungsten has been studied extensively in the past century in order to overcome issues with brittle fracture at low temperatures.  While the plastic behavior of tungsten is inherently linked to the mobility of individual dislocations, the collective motion of dislocations has strong implications for plasticity and the ultimate failure mechanisms observed at low temperatures. This study provides a detailed analysis of dislocation motion and deformation mechanisms observed in tungsten single crystals. Correlative microscopy techniques are utilized to explain strong differences in the deformation behavior of tungsten single crystals as a function of orientation. Electron backscatter diffraction and transmission electron microscopy are used to study the dislocation structure through the use of orientation imaging techniques. These results are compared with conventional dislocation imaging techniques to identify relationships between the development of microscopic dislocation structure and the resulting macroscopic deformation behavior. This work reinforces and expands our understanding of the collective role of dislocations in accommodating strain at low temperatures. 

197 - Ductile Bulk Pure Tungsten 
David Foley, Shear Form, Inc.

Pure polycrystalline tungsten is typically brittle at room temperature. An exception to this is ductile wire and sheet with elongated grains and a strong crystallographic texture. In this work we discuss the creation and properties of bulk pure tungsten with a similar microstructure developed by subjecting the material to severe plastic deformation via equal channel extrusion. Crack formation during deformation processing was a significant challenge but was mitigated by imposing hydrostatic compression during extrusion. Microstructural refinement, tungsten phase elongation, and texture changes enabled the development of increased strength, significant room temperature ductility, and barriers for crack formation and propagation.


Special Interest Program Abstracts



SIP 3-2   Flow and Spreadability Characterization of Metal Powders II: Avalanche Rheometry


550 - Blind Testing of SS-316L Metal Powders Using the Revolution Powder Analyzer 
Todd Palmer, The Pennsylvania State University - University Park

Four samples of a SS-316L powder representing virgin feedstock as well as material that had experienced multiple machine cycles in a laser-beam powder-bed-fusion process were supplied to three participating laboratories where they were subjected to dynamic flow testing at a low rotational speed (avalanche energy, break energy, avalanche angle etc.) as well as multi-flow testing over a range of rotational speeds using a Revolution Powder Analyzer. They were also subjected to a packing analysis test. The interlaboratory study was aimed at determining the discriminating capability, test repeatability and reproducibility of the tests. The participants did not know which of the powder samples represented virgin or used material. Each laboratory was requested to perform three repetitions on fresh test portions of each of the four powder samples. The test results from each of the three participants are summarized in this presentation.

557 - Evaluation of the GranuDrum® as a Tool for Standardized Powder Differentiation 
Mathieu Brochu, McGill University

The present study demonstrates a test method allowing powder differentiation using a granular material dynamic flow analyzer, namely: The GranuDrum. The study was conducted on three types of 316L stainless steel powders in categories of virgin, recycled, and a blended mixture of the former two. Three independent laboratories participated in this study and the results were compared for repeatability and reproducibility. The outcome of the present work revealed the capability of the GranuDrum to differentiate between the powders and show its sensitivity to changes in powder morphology and characteristics. The methodology also allowed determination of the critical speeds at which the powder flow regime changes between rolling, cascading, and cataracting modes with an increase in rotation speed, and how these transitions are affected by the powder characteristics. Finally, the study shows the relevance of the cohesive index measurement as a function of the rotating speed in the framework of additive manufacturing.

549-R - A Prototype of a Standard Spreadability Tester for Additive Manufacturing
Justin Whiting, Georgetown University/National Institute of Standards and Technology

We describe a simple device called the Standard Spreadability Tester (SST). The idea behind the SST is that instead of trying to predict how a powder will spread using the powder’s intrinsic properties (e.g., particle size distribution (PSD), morphology, surface, and chemical makeup) or how it performs under some other stress conditions, we subject the powder directly to conditions of stress very similar to what it sees in a Powder Bed Fusion (PBF) machine. In brief, the SST provides a test method that is straightforward and can be run in a laboratory or commercial setting. In this work, we have described the design of the device and proved the concept by preliminary testing. The remaining potential improvements have been also discussed.



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