Additive Manufacturing: Processing Effects on Microstructure and Material Performance: Al-alloys and Other Materials
Sponsored by: TMS: Additive Manufacturing Committee
Program Organizers: Eric Lass, University of Tennessee-Knoxville; Joy Gockel, Wright State University; Emma White, DECHEMA Forschungsinstitut; Richard Fonda, Naval Research Laboratory; Monnamme Tlotleng, University of Johannesburg; Jayme Keist, Pennsylvania State University; Hang Yu, Virginia Polytechnic Institute And State University

Wednesday 2:00 PM
February 26, 2020
Room: 11A
Location: San Diego Convention Ctr

Session Chair: Hang Yu, Virginia Polytechnic Institute and State University; Emma White, Ames Laboratory


2:00 PM  
Phase Transformations in Al-Ce-X Alloys: Kevin Sisco1; Alex Plotkowski2; Kurt Sickafus1; Claudia Rawn1; Ryan Dehoff2; Lawrence Allard2; Sumit Bahl2; Amit Shyam2; Andres Rossy2; Sudarsanam Babu1; 1University of Tennessee; 2Oak Ridge National Laboratory
    Additive manufacturing of aluminum alloys offers an opportunity for reduced weight and improved fuel efficiency through optimized design and replacement of heavier alloys. However, a limiting factor is the retention of strength at elevated temperatures. Recent research in Al-Ce based alloys has resulted in several compositions designed for additive manufacturing which also exhibit complex phase evolution for a wide-ranging microstructure across even a single melt pool. This variation in localized regions allows for the formation of unique intermetallic phase structures that require advanced characterization to optimize the properties of these alloys. This presentation will focus on understand both the as-fabricated structure of these alloys and the solid-state phase transformations that accompany long service times at elevated temperatures. These results will be used to rationalize the performance of these alloys, and remaining research required to properly understand the phase evolution in systems and implications for future alloy design will be summarized.

2:20 PM  
Directed Energy Deposition of AlSi10Mg: Single Track Nonscalability and Bulk Properties: Parnian Kiani1; Alexander Dupuy1; Kaka Ma2; Julie Schoenung1; 1University of California, Irvine; 2Colorado State University
    Additive manufacturing of Al alloys presents an opportunity to produce complex parts that leverage their high specific strength. The feasibility of using AlSi10Mg in laser directed energy deposition (L-DED) has not been widely studied. Therefore, this paper aims to study the effect of processing parameters on the fabrication of single-tracks, thin walls and blocks using AlSi10Mg powder in L-DED. Thin walls and single-tracks depositions were used as a guideline to deposit blocks. Blocks were deposited using L-DED, and the physical, microstructural, and mechanical properties of the samples were investigated. Results demonstrated that the morphology of the single tracks did not dictate the morphology of the bulk samples and care must be taken when transitioning from depositing single tracks to bulk samples. Results from microhardness and tensile tests show anisotropy along the build direction for elongation and ultimate tensile strength. Microhardness and yield strength, however, were mostly uniform throughout the build.

2:40 PM  
Low Surface Roughness Additively Manufactured AlSi10Mg: The Impacts on Corrosion and Water Repellency Properties: Parisa Fathi1; Mohsen Mohammadi2; Dr. Ali Nasiri1; Jonas Lunde1; 1Memorial University of Newfoundland; 2Marine Additive Manufacturing Centre of Excellence (MAMCE), University of New Brunswick
    One of the main challenges associated with the additive manufacturing of metallic components and in particular Al alloys is the high surface roughness of the parts obtained in as-printed condition, which can detrimentally affect the corrosion behavior and fatigue performance of the printed component. The present study aims to improve the surface roughness of as-printed AlSi10Mg components produced by direct metal laser sintering (DMLS) through modifying the DMLS process parameters. The electrochemical properties and corrosion resistance of the obtained surfaces were investigated by performing cyclic potentiodynamic polarization and electrochemical impedance spectroscopy, and the wettability of the fabricated surfaces was evaluated by measuring the static and dynamic contact angles on each surface. A comprehensive microstructural analysis of each sample was also conducted using optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and electron backscatter diffraction to reveal the correlation of the used DMLS process parameters and the obtained surface properties.

3:00 PM  
Fabrication Defects and Limitations in Additive Manufacturing of AlSi10Mg Lattice Structures: Enrico Ossola1; Andre Pate2; Samad Firdosy2; Andrew Shapiro2; Scott Roberts2; Eugenio Brusa1; Raffaella Sesana1; 1Politecnico di Torino; 2Jet Propulsion Laboratory, California Institute of Technology
    Additive Manufacturing has enabled the production of lattice structures with tailored mechanical properties. However, process limitations still exist, affecting the quality of the struts, practically limiting sizes and types of printable unit cells. Typically, long thin unsupported horizontal struts exhibit large deviations from ideal geometries, due to high surface roughness and internal porosity. AlSi10Mg specimens were designed and fabricated by Direct Metal Laser Sintering, considering different strut orientations, sizes and overhang lengths and using different sets of process parameters. Visual inspection, 3D scanning and microscopy inspection of the cross sections have been performed. A quality control procedure based on dimensional and geometric tolerances has been defined in order to characterize the quality of the struts. The best process parameters have been selected and used to fabricate specimens for compression tests. Finally, results of strut quality control have been used to calibrate the FEM model and replicate the experimental results.

3:20 PM  
Microstructure and Micro-mechanical Property Evolution of Cold Sprayed Al 6061 Coatings with Isothermal Heat-treatment: Benjamin Bedard1; Tyler Flanagan1; Aaron Nardi2; Avinash Dongare1; Harold Brody1; Victor Champagne2; Seok-Woo Lee1; Mark Aindow1; 1University of Connecticut; 2U.S. Army Research Laboratory, Weapons and Materials Research Directorate
    In the Cold Spray (CS) process, metallic powders are deposited using a super-sonic gas stream at relatively low temperatures. If the powder particles exceed a material-dependent critical velocity, then they bond to the substrate surface and form a dense, adherent coating. Preliminary studies on Al 6061 CS single-impact deposits and coatings have revealed baseline microstructural features, mechanical properties, as well as microstructural anisotropy between the directions parallel to and perpendicular to the spray direction. However, the dynamics of these phenomena with ex-situ heat-treatment has gone relatively unstudied. In this work, we have subjected pieces of an Al 6061 CS coating to a series of isothermal heat treatments in order to investigate the evolution of secondary phases, grains, and mechanical properties as a function of thermal history and orientation.

3:40 PM Break

4:00 PM  
Selective Laser Melting (SLM) Additive Repair of Duramold-2 Substrate Using AlSi10Mg: Edward Cyr1; Amir Hadadzadeh1; Babak Shalchi Amirkhiz1; Joshua Kelly1; Mohsen Mohammadi1; 1Marine Additive Manufacturing Centre of Excellence
    Additive repair by the process of directly printing metals onto damaged parts has significant potential to reduce costs of maintenance and repair operations, especially in the marine and shipbuilding industry. In this study, additive repair of Duramold-2™ (Al-Cu-Ni-Fe-Mg) cast alloy was conducted by deposition of AlSi10Mg through selective laser melting (SLM). The microstructure of the additively repaired aluminum, including the interface, was investigated using advanced electron microscopy techniques. Excellent bonding between the AlSi10Mg and Duramold-2™ substrate was observed. Mechanical assessment of repaired samples, including micro-hardness measurements and uniaxial tensile testing, supported the microscopy observations. The fracture surface of tensile specimens was also investigated, where failure was consistently observed in the substrate. The SLM-AlSi10Mg repair material reliably possessed better performance than the substrate, mainly due to its refined microstructure.

4:20 PM  
Microstructure Distribution, Phase Identification, and Texture of Selective Laser Melted GRCop-84 in As-built and HIPed Conditions: Robert Minneci1; Claudia Rawn1; Sudarsanam Babu1; Michael Haines1; Jeffrey Bunn1; 1University of Tennessee
    GRCop-84 or Cu-8 Cr-4 Nb At% is an alloy with exceptional high temperature properties developed by NASA. GRCop-84 can be formed into hardware by powder processing techniques that preserve small Cr2Nb C15 Laves phase precipitates and a relatively pure Cu matrix which yields improved thermal conductivity and mechanical strengthening. Additive manufacturing (AM) techniques like selective laser melting (SLM) has produced GRCop-84 components with properties equal to or better than traditionally wrought. EBSD, SEM, high temperature and ambient XRD have been performed on SLM samples made by NASA MSFC in as-built and HIPed conditions to investigate the microstructure. EBSD and SEM have shown complex grain structures, texture, and particle distribution caused by unique interactions of AM and the Cr2Nb particles. X-ray diffraction results have shown 0.1 At% Cr2Nb in the as-built condition that returns to 12 At% after high temperature exposures.

4:40 PM  
Effect of Cyclic Rapid Thermal Loadings on the Microstructural Evolution of a Cantor Alloy During Selective Laser Melting Processes: Hao Wang1; Zhiguang Zhu2; Hansheng Chen1; Sharon Mui Ling Nai2; Rongkun Zheng3; Sophie Primig4; Sudarsanam Babu5; Simon Ringer1; Xiaozhou Liao1; 1School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney; 2Singapore Institute of Manufacturing Technology; 3School of Physics, The University of Sydney; 4School of Materials Science & Engineering, UNSW; 5Department of Mechanical, Aerospace and Biomedical Engineering, The University of Tennessee, Knoxville
    The additive manufacturing processes of metallic materials consist of cyclic rapid thermal loadings that affect significantly the microstructure and consequently the mechanical properties of materials. Here we used a FeCoCrMnNi high-entropy alloy as the model material to explore the effects of cyclic thermal loadings on local microstructure and mechanical properties. Transmission electron microscopy and atom probe tomography were used for structural characterisation. Results showed that, with the increase of the number of cyclic thermal loadings, the microstructure evolved from a nanocrystalline structure in the top layer, through coarse grains with cellular dislocation structures in a middle layer, to nanotwin and hierarchical nanotwin structures in the bottom layer. Significant Mn and Ni segregations at dislocation cell wall areas were observed. Mn and O rich precipitates were observed along the dislocation walls. The impact of local microstructure and elemental distribution on the mechanical properties of the material will be discussed in detail.

5:00 PM  
Experimental Evaluation of Additively Manufactured Continuous Fiber Reinforced Nylon Composites: Mahdi Mohammadizadeh1; Ismail Fidan1; 1Tennessee Technological University
    Continuous fiber reinforced additive manufacturing (CFRAM) is a promising fabrication technology with a wide range of potential applications in different industries. The potential applications of CFRAM components justify the need for investigation of their thermomechanical properties. In this study, Dynamic Mechanical Analysis (DMA), tensile, and thermal properties of CFRAM components was studied and the effect of fiber percentage on properties was investigated. Nylon was used as thermoplastic polymer matrix and carbon fiber (CF), and fiber glass (FG) as reinforcing agents. It is found that fiber reinforcement improves storage modulus, loss modulus, tensile strength, elastic modulus, thermal conductivity and heat conduction of nylon. Scanning Electron Microscope (SEM) was used to study printing quality, fiber-matrix interface and microstructure of composite. The final results in this research study present the basis for industrial applications of fiber reinforced thermoplastic polymers for industrial applications.

5:20 PM  
Small-scale Characterization of Wire-Arc Additive Manufactured Nickel Aluminum Bronze Alloy: Meysam Haghshenas1; Xinyu Song2; Devendra Verma3; Dharmendra Chalasani4; Mohsen Mohammadi4; 1University of Toledo; 2Weifang University; 3Nanoscience Instruments; 4University of New Brunswick
    Nickel aluminum bronzes (NABs) are microstructurally complex alloys which typically contains α-phase (Copper), some retained β-phase, and four types of κ-intermetallic phases in the as-cast condition. NABs are widely used in marine and aerospace industries, and also find applications in production of pressure vessels, condenser systems, and desalination plants where the high-temperature (423-523 K) properties are important to assess. In the present study, a wire-arc additive manufacturing (WAAM) technique was used to produce NAB square bars to minimize porosity and thereby achieve superior properties. In a view to correlate the local mechanical properties with the microstructure at ambient and elevated temperatures (i.e. 298 K to 523 K), semi-destructive instrumented nano-indentation along with optical and scanning electron microscopies were employed on the wire-arc additive manufactured NAB. The effects of indentation size, indentation strain rate (i.e. strain rate sensitivity), and their dependencies upon indentation depth were then correlated.