Members Who Attended
Richard D. Sisson, Jr., Danielle Cote, Diran Apelian, Diana Lados, Jianyu Liang
Kyle Fitzpatrick-Schmidt, Sean Kelly, Carl Soderhjelm, Derek Tsaknopoulos, Caitlin Walde, Yangzi (Sophie) Xu, Aaron Birt, Yuwei Zhai, Baillie McNally, Guannan Guo, Xiaoqing Cai, Anbo Wang, Haixuan Yu
Professor Diran Apelian, Founding Director of our Metal Processing Institute, received the ASM Gold Medal at the Annual Meeting (MS&T) on October 25, 2016 in Salt Lake City, Utah. The ASM Gold Medal is among the most prestigious awards of the Society. Established in 1943, the Gold Medal recognizes outstanding knowledge and great versatility in the application of science to the field of materials science and engineering, as well as exceptional ability in the diagnosis and solution of diversified materials problems.
Thermodynamic & Kinetic Model Application to Strengthening Mechanisms of Aluminum Alloys for Additive Manufacturing
Authors: Derek Tsaknopoulos, Danielle Cote, Richard Sisson, Jr., Victor Champagne
While gas-atomized powder has become a staple feedstock material for additive manufacturing, detailed understanding regarding the mechanical properties of the raw material is needed for superior process modeling. Focusing primarily on the yield strength of the feedstock powder, various strengthening mechanisms are considered for the contributions from solid solution strengthening, grain size strengthening, precipitation, and dispersion mechanisms. These equations utilize the quantified kinetic and thermodynamic outputs from modeling software Thermo-Calc, JMatPro®, and TC-PRISMA. The data from these models coupled with the strengthening contributions progress into a strengthening model that represents the overall strengthening influence of each mechanism for specified gas-atomized powders. The effectiveness of this strengthening model is determined using thermal, optical, and mechanical characterization methods.
Application of Computational Thermodynamics & Kinetics to Rare Earth Reduction in Magnesium Alloys
Magnesium alloys are widely used in numerous applications due to their extremely low density. Through the addition of rare earth metals, the high temperature capabilities of magnesium alloys are increased by creation of thermally stable secondary phases. This research is focused on reducing the amount and number of rare earth elements used in these alloys, while simultaneously maintaining the high temperature capabilities and low density. Thermodynamic, kinetic, and strengthening mechanism models have been used to analyze the magnesium alloy EZ33A and seven new compositions with varied amounts of rare earths and additional elements. The theoretical analysis was followed by experimental investigation of the new alloy compositions.
The Microstructural Evolution of Powder Aluminum Alloys after Thermal Processing
Gas-atomized metallic powders are commonly used in additive manufacturing processes. While their post-process consolidated properties are widely studied, there is little research on the properties of the powders before processing. Understanding the powder characteristics before use in additive manufacturing could lead to fine-tuning properties of additively manufactured materials. 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 to those predicted through modeling.
Comparison of Annealing and Hot Isotactic Pressing for Post Processing Heat Treatment of Direct Metal Laser Sintered Ti6Al4V
Ti6Al4V is a popular alloy for orthopedic applications in hip replacement, total knee replacement and dental implants. Due to the advantage of additive manufacturing techniques in producing highly customized parts, it has the potential to be applied in the orthopedic industry. However, the as-fabricated part possesses an acicular martensite structure with poor ductility and anisotropic properties. Corrosion and wear of Ti6Al4V in the hip replacement is currently the main concern on revision surgery. Therefore, proper post- treatments are required for the as-fabricated parts. In this paper, comparisons of annealing and hot isotactic pressing (HIP), as the post-treatments for directed metal laser sintered Ti6Al4V, are presented. The microstructures were examined using Scanning Electron Microscopy and X-ray diffraction. The residual stress was also measured by X-ray diffraction. The comparisons of corrosion resistance with different post-treatments are presented and discussed.
Metallurgical Bonding between Cast-In Ferrous Inserts and Aluminum
Cast-in ferrous inserts in aluminum castings made via die casting processes can provide local improvement of properties such as wear resistance, corrosion resistance, heat transfer, and strength. The bond between the insert and the casting will greatly influence the overall performance. There are two distinct types of bonds between a ferrous insert and the aluminum casting; a mechanical bond and a metallurgical bond, the latter being the focus of this work. The short solidification times associated with die casting processes limit diffusional processes, however nucleation and growth of the metallurgical bond on the steel insert does take place and the kinetics are critical in controlling the integrity of the bond. This work is directed at developing a more generic method to metallurgically bond the insert to the casting by application of low melting point coatings. Results will be presented and discussed
Sustainable Metal Production of Aluminum: Goodbye Smelting Plants; Hello Mini Mills
Aluminum (Al) usage in the automotive industry is projected to increase annually, however, the sustainability of this demand increase is under speculation due to a misunderstood recycling rate for automotive aluminum. Al as a lightweight choice material is not only recyclable, but the supply chain of available scrap will make it amenable to produce Al from a 100% previously used metal. The high efficiencies of current recycling technologies and operations are reviewed in this presentation. We will present end of vehicle life recycling rate of aluminum and its alloys within the United States’ automotive sector. A holistic and detailed understanding of the processes, technologies and their effectiveness, regarding the extraction of aluminum from end of life automobiles, and the resulting material flows are reported. A grave-to-gate, material flow analysis approach is used to determine the recycling rate of automotive aluminum/aluminum alloy metal units. The automated Al mini mill is the future pathway for a sustainable production of Al.
Microstructure, Tensile Properties, and Fatigue Crack Growth Behavior in Inconel 718 Manufactured by Laser Engineered Net Shaping
Laser Engineered Net Shaping (LENS) is a selective deposition based Additive Manufacturing technique developed for fabricating metallic materials. Applying LENS to critical fields such as aerospace, defense and medical requires thorough understanding of the LENS-fabricated materials. In this study, Inconel 718 builds were fabricated at two laser power levels, and were investigated in both as-fabricated and heat treated conditions. The effects of processing parameters and heat treatment on microstructure and room temperature tensile properties were systematically studied. Room temperature fatigue crack growth (FCG) tests were also performed to investigate the FCG behavior, as well as to establish the crack propagation mechanisms at the microstructural scale in this alloy. The results generated contributes towards a better understanding of the processing – microstructure – mechanical properties relationship in LENS fabricated Inconel 718.
Microstructure Evolution, Tensile Properties, and Fatigue Crack Growth Mechanisms in Ti-6Al-4V Fabricated by Electron Beam Melting
Electron Beam Melting (EBM) is an additive manufacturing technique that selectively fuses powder particles on a powder bed using electron beam as a power source. The unique thermal history of EBM process leads to directional microstructure and consequently, anisotropy in mechanical properties. In this study, Ti-6Al-4V fabricated by EBM was systematically investigated. As-fabricated microstructure was first characterized, and altered through various heat treatments. Room temperature tensile and fatigue crack growth (FCG) properties were then evaluated and compared in different orientations with respect to the deposition direction. The effects of heat treatment on the tensile and FCG properties of the material were determined. Fatigue crack growth mechanisms at the microstructural scale were also established. These results will be systematically presented.
The Effects of Induction and Furnace Tempering Parameters on the Microstructure, Mechanical Properties and Fatigue Performance of Quenched and Tempered AISI 4140 Steel
Induction and furnace tempering can be used to achieve equivalent mechanical properties in quenched and tempered martensitic steels. Typically induction tempering takes place at higher temperatures for a matter of minutes while furnace tempering is conducted at lower temperatures for longer times. This paper presents the experimental results of controlled furnace and induction tempering heat treatments with particular attention to microstructure, mechanical properties and fatigue behavior for AISI 4140 steel. It was found that the size, morphology, and number density of carbides present are strongly influenced by the tempering process. The mechanical properties of tensile strength, ductility and impact toughness are a function of the microstructure. The torsional fatigue performance is also a function of processing parameters and microstructure. These results have widespread impact in several industrial applications relying on both furnace and induction quench and temper operations.
Experimental Verification and Computational Modeling for High Strain Rate Additive Manufacturing
High strain rate additive manufacturing processes, such as the cold spray process, are successfully being used for military repair applications. However, this process is in need of an all-encompassing model that will predict the final mechanical properties of the cold sprayed material, which is a function of raw material and processing parameters. A through-process model has been created and incorporates the gas-atomized powder microstructure, the powder pre-treatment, the cold spray particle impact, and post-processing. Current work focuses on the characterization of the microstructural evolution of several cold sprayed aluminum alloys to verify and enhance the computational models that make up the powder production and impact stages of the model. Microstructural morphology, phase identification, and properties of various aluminum alloys powders and cold sprayed deposits are determined through scanning and transmission electron microscopy, and nanoindentation.
Development of Wear Resistant WC Metal Matrix Composites Consolidated via Laser-Assisted Cold Spray
Extreme wear and corrosion resistance are common property requirements in aerospace, energy, and defense sectors. The push for longer part life and greater durability has resulted in a number of novel ways to produce protective coatings. One such method, Laser-Assisted Cold Spray (LACS), has been demonstrated to be extremely effective at consolidating a wide range of carbide-based materials. However, there are a variety of materials that must be protected and many different coating compositions that may be applied. Tungsten carbide based ceramics with metallic binders of varying compositions from 7 to 40% have been consolidated via the LACS process. These MMCs have been consolidated onto a wide range of materials including cast iron, 316L stainless steel, titanium, and low-carbon steel. Hardness profiles, microstructures, porosity, and basic adhesion will be discussed is they relate to the optimal coating qualities for all material combinations.
Life Extension of High Temperature Structural Alloys by Surface Engineering in Carburizing Atmospheres
The heat-treating industry is in need of heat-treatment furnace materials and fixtures that have a long service life and reduced heat capacity. Aluminizing is widely used to increase the high temperature oxidation and carburization resistance of nickel-based alloys. In this paper RA330, RA602CA, 304L, Inconel 625 alloys were selected to study their performance in an industrial carburization furnace for times up to one year. These alloys were exposed in both the as-fabricated and aluminized condition. The test samples were exposed to 0.7%C carburizing atmosphere at approximately 900 for 3 months, 6months, and 12months. The oxidation properties and oxide stability at high temperatures will be presented. In addition, the preliminary analysis of microstructural development during long term exposure experiments in an industrial carburizing furnace will be presented. These samples were characterized using optical and scanning electron microscope, EBSD, and x-ray diffraction. It was found that the aluminized alloys exhibited lower weight gain and carbon uptakes.
A Microstructural Study of RA330 and Aluminized RA330 in a Gas Carburizing Furnace
High temperature corrosion resistant alloy RA330 is widely used for furnace fixtures in heat treatment processes. Aluminizing can be used to increase the high temperature oxidation and carburization resistance of nickel-based alloys. In this paper RA330 and Aluminized RA330 were selected to study their performance in an industrial carburization furnace for times up to one year. The oxidation properties and oxide stability at high temperatures will be presented. In addition, the preliminary analysis of microstructural development during long term exposure experiments in an industrial carburizing furnace will be presented. These samples were characterized using optical and scanning electron microscope, EBSD, and x-ray diffraction. It was found that the aluminized alloys exhibited lower weight gain and carbon uptakes.
An Enhancement to the Low Pressure Carburizing Simulation
The low pressure carburizing (LPC) process is receiving increased attention due to its low environmental impact and the potential for decreased cycle times. In addition, there can be reduced distortion and much less intergranular oxidation. CarbToolⒸ developed by CHTE at WPI has been an effective tool for the simulation of LPC processes. Initially the average carbon flux was initially used as the surface boundary condition which was calculated from experimental data. Considering the potential for a carbon deposit formed on the surface, the boundary condition was modified to improve the LPC process simulation. Experiments were designed to fully identify the surface properties with carbon deposit. An enhanced model using the carbon potential in the low pressure atmosphere as boundary condition for LPC process is proposed. The results of these experiments will be presented and discussed. This data is used to enhance the modeling in CarbToolⒸ.