145th Annual Meeting and Exhibition
February 14 – 18, 2016
Nashville, Tennessee USA
Our Members Who Attended
Diran Apelian, Diana Lados, Brajendra Mishra, Yiming Rong, Danielle Cote
Xiang Chen (Post Doc), Tiantian Zhang (Post Doc)
Inigo Anza, Aaron Birt, Robert DelSignore, Mikaela Derousseau, Kyle Fitzpatrick-Schmidt, Shaymus Hudson, Sean Kelly, Baillie McNally, Yi Pan, Carl Soderhjelm, Anthony Spangenberger, Derek Tsaknopoulos, Caitlin Walde, Yuwei Zhai
A Study of the Microstructural Evolution of Powder Aluminum Alloys after Thermal Processing
Caitlin Walde, Danielle Cote, Richard Sisson
Gas-atomized metallic powders are used in the additive manufacturing industry, and their post-processed properties are widely studied. However, little research has been done on the properties of the powders before processing, and how these properties may differ from those of a bulk sample of the same alloy. Understanding the characteristics of the powder before processing could lead to fine-tuning of the properties after the additive manufacturing process. This research studies the effect of various heat treatment processes on the characteristics and microstructural evolution of powder aluminum alloys. Treatment times and temperatures were guided by thermodynamic and kinetic modeling. Optical microscopy, scanning electron microscopy, and nanohardness were used to evaluate each condition. Experimental results are compared model predictions.
Verification of a Predictive Strength Model for Gas-Atomized Aluminum Powder
Baillie McNally, Danielle Cote, Victor Champagne, Richard D. Sisson, Jr.
For certain solid-state additively manufactured processes, more attention is being given to the initial mechanical properties of feedstock powder as they play a role in determining the final properties of the deposit. To quantify the mechanical properties of the powder, and therefore predict the performance of the consolidated material, a predictive strength model is being developed that considers strengthening contributions from solid solution, precipitation, and microstructure. The results of the additive strength model are experimentally verified for several aluminum alloys including Al 2024, 5056, 6061, and 7075. Characterization techniques including scanning and transmission electron microscopy, x-ray diffraction, and differential scanning calorimetry are utilized.
Microstructure Evolution, Tensile and Dynamic Properties, and Computational Modeling in Ti-6Al-4V and Inconel 718 Alloys Manufactured by Laser Engineered Net Shaping
Yuwei Zhai, Diana Lados
Laser Engineered Net Shaping (LENS) is a powder-based Additive Manufacturing process able to fabricate fully dense metallic parts. Applying it to structural aerospace components and repair requires a fundamental understanding of both the microstructures and static and dynamic properties of the LENS-fabricated materials. In this study, Ti-6Al-4V and Inconel 718 alloys were fabricated using two laser power levels for each alloy, and were investigated in both as-fabricated and heat treated conditions. First, the effects of processing parameters and heat treatment on microstructure and tensile properties were systematically studied. Computational modeling tools have been developed to evaluate the thermal histories of the depositions and uniquely predict their resulting microstructures. Further, room temperature fatigue crack growth tests (R=0.1, 0.8) were performed in different orientations with respect to the deposition direction, in order to establish the crack growth mechanisms at the microstructural scale of the alloys. The results will be compared and critically discussed.
Scrap Characterization to Optimize the Recycling Process
Sean Kelly, Diran Apelian
The rise in world population and push towards global urbanization is causing the consumption of materials and natural resources to increase rapidly. Understanding end-of-life material streams is critical so proper recovery and recycling techniques can be enforced. The use and reuse of aluminum are of prime importance when considering the future of the lightweight infrastructure of transportation vehicles to increase fuel economy as oil supply is a globally trending concern. Non-ferrous auto-shred scrap metal is a major end-of-life metal stream that must be recovered and recycled effectively and efficiently to ensure the maximum longevity of each metal constituent’s total in-use lifetime. This work is focused on the characterization of metal scrap classes that are shredded, old aluminum alloys to determine the necessary parameters that should be utilized to help develop this vacated recycling technology.
Microstructure Evolution, Tensile Properties, and Thermo-Mechanical Modeling in Wrought and Cast Aluminum Alloys Fabricated by Friction Stir Processing and Welding
Friction stir welding and processing (FSW/FSP) are solid-state techniques widely used for joining and repairing in the transportation sector, and understanding their effects on static and dynamic properties is critical for structural integrity. In this study, four aluminum alloy systems (wrought 6061 and cast A356, 319, and A390) were friction stir processed using various processing parameters in both as-fabricated and pre-weld heat treated conditions. The effects of processing and heat treatment on the resulting microstructures, hardness/micro-hardness, and tensile properties were systematically investigated and mechanistically correlated. Tensile tests were performed in room temperature air. Optimum processing parameters domains that provide both defect-free welds for each alloy. A thermos-mechanical model of FSW was developed to predict the temperature and stress history of the welds.
Fatigue Crack Growth in Structural Cast Aluminum Alloys: Microstructural Mechanisms, Modeling Strategies, and Integrated Design
Anthony Spangenberger, Diana Lados
Fatigue crack growth (FCG) studies were performed on solution-strengthened (A535) and precipitation-strengthened (A356, 319) cast aluminum alloys. Microstructures were altered through processing, chemistry, and heat treatment in order to systematically investigate the individual and combined effects of materials’ characteristic microstructural features on FCG. Long FCG tests were performed on compact tension specimens at room temperature and three stress ratios (R=0.1, 0.5, 0.7). Additional small FCG tests were conducted on corner flaw tension specimens at R=0.1. FCG mechanisms at the microstructural scale of the studied alloys were identified, and load-microstructure-damage mechanisms design maps were created. A methodology for data treatment and long-to-physically small crack growth corrections has been developed, and an original model that further incorporates the microstructurally small crack growth behavior was created. A comprehensive ICME toolset for simulating and predicting microstructure-dependent FCG and evaluating component lifetime was also developed and will be discussed.
Fatigue Crack Growth Modeling and Mechanisms in Engine Materials under Hot Compressive Dwell Conditions
Xiang Chen, Diana A. Lados, Richard G. Pettit, David Dudzinski
Fatigue crack growth (FCG) under Hot Compressive Dwell (HCD) conditions, a special case of creep-fatigue occurring under compressive stress, is an important failure mode in many high temperature applications. Tensile residual stresses building up at the crack root are considered a key factor contributing to FCG under HCD conditions. To understand and quantify this effect, a physics-based model was developed, in which the residual stress contributions are added to the elastic and plastic responses of the material to predict the behavior. In contrast with the existing complex models, this approach is simple, easy to apply, and generates good predictions. Results from both isothermal and non-isothermal tests were compared in this study. Comprehensive SEM/TEM studies were also performed to understand HCD effects at the microstructural scale of two engine alloys (cast Al-319 and IN718), and recommendations will be given to optimize the materials’ microstructures for high temperature applications.
TiB2 Particle Detection in Liquid Aluminum via Laser-Induced Breakdown Spectroscopy
S.W. Hudson, J. Craparo, R. De Saro, D. Apelian
Because aluminum alloy castings are becoming commonplace for critical applications in the automotive and aerospace industries, tight control over the cleanliness of the melt (mitigation of solid particle inclusions) and microstructure must be achieved. In order to control cleanliness, it must first be well defined and measured. Very few techniques exist in industry that can quantitatively measure inclusion levels in-situ. Laser-induced breakdown spectroscopy (LIBS) is presented as a promising technique to quantify solid particles, desired or undesired, in aluminum melts. By performing LIBS with subsequent statistical analysis on liquid Al with varying amounts of TiB2 particles, calibration curves for B and Ti were generated.
Improvement in Resource Productivity by Life Extension through Corrosion Control: An Educational Perspective
Materials are non-renewal resources that are created through an ‘unnatural’ process. In addition to resource recovery and recycling of valuable materials to achieve sustainability, simple methods to extend the life of materials enhance the resource productivity. The natural process of corrosion tries to reverse the process of material extraction causing enormous loss of energy and impacts the environment. Corrosion costs the U.S. over $300 billion per year and also produces significant safety hazards. Corrosion control is, therefore, important to enhance the life of engineering metals and materials, which is also the focus of many government regulatory agencies such as the EPA, DOT and OPS. Corrosion protection technology utilizes metallurgy, material chemistry and physics as well as electricity to prevent or control corrosion degradation and therefore, the education of corrosion science & engineering is directly linked to improving material life. Education in corrosion Control applies these sciences to control the chemical and mechanical aspects that are involved in the deterioration of properties. This paper will address the educational aspects of corrosion Technology that allow resource productivity improvement of materials.
Rare Earth Metals Recycling from Spent CFLs and Permanent Magnets
Brajendra Mishra, Patrick Eduafo, Mark Strauss & Caleb Stanton
Many Rare Earth metals, including yttrium and scandium, are being increasingly used in clean energy technologies and energy device components, such as, colored phosphors, lasers, catalysts and high intensity magnets. The commitment to clean energy technologies by the scientific community and the projected growth in power and transportation sectors across the globe ensure that the demand for rare earth metals and compounds would continue to escalate. This demand implies that, to ensure unhindered technological innovation, it is essential to possess secure supply chains for rare earth elements. In order to ensure secure rare earth supply and attenuate supply-demand imbalance, it is of utmost importance to look at opportunities to process intelligently, recycle and reuse Rare Earth Elements from secondary sources, such as post-consumer and manufacturing process wastes. Economic and political considerations have caused significant fluctuations in rare-earth metals availability which requires that better extraction techniques, alternative uses, recycling opportunities should all be simultaneously explored.
Recovery of Aluminum from the Aluminum Smelter Baghouse Dust
Myungwon Jung, Brajendra Mishra
The extraction of metals from a primary or a secondary resource is achieved by pyrometallurgy and hydrometallurgy. Currently, most of metal production plants consist of both pyrometallurgical and hydrometallurgical processes. Dust generation during the processes is one of the disadvantages of pyrometallurgical plants. Therefore, dust collection systems are installed in metal production plants to capture the emission of air pollutants from their off-gases. Due to environmental problems associated with the dust and high cost of disposal, proper treatments are required to minimize these problems. Recycling some metals from the dust during waste treatment could be a good way to utilize metal resources. In this research, alkaline leaching on the aluminum smelter baghouse dust has been studied with different reagents, bath temperature and pulp densities. Based on the alkaline leaching tests, the recovery of aluminum is high with sodium hydroxide at high temperature and low pulp density. HSC chemistry analysis shows that the product of NaOH leaching on the aluminum smelter baghouse dust is the sodium aluminate.
Synthesis of Al-TiC Nanocomposites by an In-Situ Gas-Liquid Method
Inigo Anza, Makhlouf Makhlouf
Next generation of aluminum automotive engines will have to operate at temperatures approaching 3000C. Traditional aluminum alloys cannot perform at these temperatures, but aluminum alloys reinforced with nanoparticles can. The synthesis of aluminum-titanium carbide nanocomposites by an in-situ gas-liquid reaction implies methane to be injected into molten aluminum that has been pre-alloyed with titanium. The gas is introduced by means of a rotating sparger-impeller unit into the hot alloy, and under the correct conditions of temperature, gas flow and rotation speed, it reacts preferentially with titanium to form titanium carbide nanoparticles that are well dispersed in the metal matrix. The apparatus design, the multi-physics phenomena and a mechanism proposal for nanoparticles formation is first given. The operation window in which to allocate the parametric analysis is next calculated. Finally, characterization of initial obtained material, its relationship to the processing parameters and guidelines to obtain the nanoparticles is done.
Nano-Strength Testing of Additive Manufactured Parts Using Atomic Force Microscopy
Robert C. DelSignore
Additive manufacturing (AM) is growing in popularity in the automotive, aviation, military, medical, and prototyping industries. Therefore, it is important to understand the mechanical properties of parts built in a layer by layer fashion as a function of the manufacturing process parameters. This study describes how atomic force microscopy can be used to determine inter-layer bond strengths and, more specifically, powder particle-substrate adhesion strengths in AM applications, particularly cold spray. Individually bonded particles are sectioned from substrate materials and are formed into small cantilever specimens. By applying a known force to the micro-cantilevers, resolved stresses are determined at the particle-substrate adhesion zone. Loads are increased until fracture occurs, corresponding to the critical stress required for inter-layer separation. Analysis with scanning and transmission electron microscopy identifies the location and method of fracture. Fracture mechanics is then applied to determine critical flaw sizes for the manufacturing parameters. Ultimately correlation between processing variables and flaw sizes enables design optimization.