Additive Manufacturing: Building the Pathway towards Process and Material Qualification: Novel Techniques
Sponsored by: TMS Extraction and Processing Division, TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Powder Materials Committee, TMS: Process Technology and Modeling Committee, TMS: Additive Manufacturing Bridge Committee
Program Organizers: John Carpenter, Los Alamos National Laboratory; David Bourell, University of Texas - Austin; Allison Beese, Pennsylvania State University; James Sears, GE Global Research Center; Reginald Hamilton, Pennsylvania State University; Rajiv Mishra, University of North Texas; Edward Herderick, GE Corporate
Wednesday 2:00 PM
March 1, 2017
Location: San Diego Convention Ctr
Session Chair: Andrew Shapiro, Jet Propulsion Laboratory; Carolyn Seepersad, University of Texas - Austin
Aerospace Applications for Additive Manufacturing: Andrew Shapiro1; John Paul Borgonia1; Nataly Chen1; R. Peter Dillon1; Bryan McEnerney1; Raul Polit-Casillas1; Lewis Soloway1; 1Jet Propulsion Laboratory, California Institute of Technology
Until relatively recently, additive manufacturing had been used primarily with polymers for prototyping and modeling applications. Currently, additive manufacturing is starting to be used more widely for printing metals and ceramics. Several metals are starting to be used very extensively including Ti, Fe and Al alloys, making additive manufacturing relevant for space flight applications. This presentation is a review of several of the applications that are pertinent to space flight use. Seven primary applications in aerospace are identified where additive manufacturing can potentially provide a clear benefit. In addition, several targeted areas including processing parameters, post-processing parameters, materials selection and qualification processes have been identified that need to be considered with respect to the applications. The applications include specific uses such as mass reduction or in-situ fabrication, as well as innovative design strategies that take advantage of the unique capabilities that additive manufacturing has to offer.
Additive Friction Stir: A New Additive Manufacturing Technology for Metallic Structural Materials Including Ti64: Jianqing Su1; Nanci Hardwick1; 1Aeroprobe Corporation
Development of additive manufacturing (AM) has opened up new opportunities for fabrication of metallic structural materials. Additive Friction Stir (AFS) is a new technology being developed at Aeroprobe Corporation, which can be used for additive manufacturing, coating, and joining. Because it is a solid-state process, AFS eliminates problems such as porosity, hot cracking, segregation and dilution which are commonly associated with fusion-based techniques to create high quality parts. Using AFS, many metallic materials including Al alloys, Mg alloys, Cu alloys, Ni-based superalloys and steels have been successfully deposited at Aeroprobe. In this presentation, AFS deposition of Ti-6Al-4V, the most widely used titanium alloy, will be discussed. The microstructure and mechanical properties of AFS Ti-6Al-4V will be studied. It is expected that AFS processing can create small prior- grains with fine - lamellar structure in deposited Ti-6Al-4V alloy, leading to improved mechanical properties.
Nanomechanical and EBSD Characterization of Additive Manufactured Mg Alloys: Paul Allison1; Oscar Rivera1; Wilburn Whittington2; Brian Jordon1; Jianqing Su3; Nanci Hardwick3; 1University of Alabama; 2Mississippi State University - Center for Advanced Vehicular Systems; 3Aeroprobe Corporation
The Solid State Additive Manufacturing (SSAM) process referred to as Additive Friction Stir (AFS) provides a new path for repair, coating, joining and additively manufacturing materials such as magnesium alloys. This additive manufacturing process differs from traditional friction stir welding/processing since additive material is fed through a non-consumable rotating cylindrical tool generating heat and plastically deforming the feedstock material through controlled pressure from the tool as successive layers are built upon a substrate. In this research, the dynamic recrystallization and grain refinement was characterized for the successive layers in as-deposited WE43 using Electron Backscattered Diffraction (EBSD). The EBSD results depicted grain structures formed by dynamic recrystallization (DRX) with finer grain structures forming at the layer interfaces. Nanoindentation performed on the deposited WE43 was spatially correlated to scanning electron microscopy – energy dispersive X-ray spectroscopy (SEM-EDX) to provide relationships of the modulus and hardness to the indent chemical composition.
Scaling Relationships for Direct Ink Writing with Acoustic Focusing: Leanne Friedrich1; Rachel Collino1; Tyler Ray1; Matthew Begley1; 1University of California Santa Barbara
Novel methods to control the microstructures of multiphase extruded materials can introduce spatial variations in structural and functional properties to additively manufactured components. One promising method is acoustic focusing, wherein microparticles suspended in fluids are extruded through a silicon microfluidic channel, and a piezoelectric actuator manipulates microparticle motion by establishing an acoustic wave in the channel. Acoustic focusing quality depends on factors including nozzle and particle geometries, acoustic pressure, matrix rheology, and flow characteristics. Using these factors, we experimentally verified scaling relationships governing acoustic focusing using ceramic microspheres in epoxy resin. Further experiments characterized focusing behavior in more complex shear-thinning matrices composed of epoxy resin, fumed silica, and acetone. We designed image processing methods to quantify particle focusing and form holding (the ink’s ability to maintain shapes), and we used those methods to identify the trade-offs associated with matrix formulation, printing speed, and acoustic pressure.
3:20 PM Break
3:40 PM Invited
Statistical Design Guidelines for Powder Bed Fusion: Carolyn Seepersad1; Jared Allison1; Conner Sharpe1; Steven Kubiak2; 1University of Texas at Austin; 2Stratasys Direct Manufacturing
Many engineers find it difficult to utilize additive manufacturing because of a lack of “Design for AM” knowledge in the public domain. Reliable information on material properties and geometric specifications is often scattered throughout the literature, if it is publicly available at all. The objective of this research is to create design guidelines for dimensioning parts that are additively manufacturing using powder bed fusion technology, particularly selective laser sintering (SLS). The guidelines are based on a series of experiments designed to determine the limiting feature sizes, accuracy, and repeatability for various types of features fabricated in commercially available SLS machines. The features include concentric rings, rods, slots, holes, letters, and snap-fit assemblies, plus mechanical properties and surface finish. Statistical data is gathered from multiple machines, orientations, and locations within the build chamber. The result is one of the largest publicly available databases on design allowables for any additive manufacturing process.
Characterization of Additive Manufactured IN718 Using Ultrasonic Measurements: Paul Panetta1; Hualong Du1; Waled Hassan2; 1Applied Research Associates, Inc.; 2Rolls-Royce Corporation
Additive manufactured materials have the potential to make a great impact on manufacturing, but the microstructures of these materials are complex in their morphology, residual stress and texture. We developed ultrasonic measurements to map the 3-D spatial distribution of grain morphology in IN718 nickel superalloy manufactured through direct laser deposition (DLD) process. Ultrasonic measurements were performed by using two focused transducers in the pitch-catch configuration to collect ultrasonic scattering from grain boundaries in various directions. Ultrasonic scattering is significantly sensitive to the mean grain size and grain morphology. The 3-D spatial distribution of grain morphology was measured by comparing the root mean square (RMS) curves of ultrasonic scattered signals captured in various directions. In this work we are able to determine the direction and degree of elongation of dendritic grains. These measurements can be used for qualifying the material and the process as well as provide feedback during fabrication.
Control of Deposition Interface Quality in Additive Manufacturing: Cameron Knapp1; John Carpenter1; Desiderio Kovar2; 1Los Alamos National Laboratory; 2University of Texas at Austin
In order to explore the feasibility of the repair of components using directed energy deposition; LANL has initiated research into the quality of the interface between the substrate and deposited metal. Previously obtained data has shown that low initial inter-pass temperatures, like that of the first pass on a cold substrate, results in increased porosity and lack of fusion defects. The size and population of these defects are unacceptable for component repair applications and components designed with integrated substrates. Experiments were conducted on a LENS MR-7 using the laser to preheat substrates to elevated temperatures prior to a controlled deposition. Critical deposition parameters were monitored in situ using a side-view IR camera and co-axial two-color pyrometer. Ex situ metallography was conducted to quantify inter-layer porosity and lack of fusion defects. The combination of in situ monitoring and ex situ metallography was used to correlate critical deposition parameters to defect introduction.
Matrix Grain Refinement in Functionally Graded Ti-6Al-4V/TiB Composite Fabricated by LENS Additive Manufacture: Denver Seely1; Hongjoo Rhee1; Mark Horstemeyer1; 1Mississippi State University/Center for Advanced Vehicular Systems
The blown powder method of metal additive manufacture provides access to a new design space for composites. By modulating the composition of the deposition melt pool through powder mixing, spatial variation of material properties can be achieved and be tailored in functionally advantageous arrangements. Mechanical properties of deposited titanium alloys are dominated by process dependent microstructure features; of central importance is initial solidification grain size. The eutectic solidification of titanium boride provides a compositionally controlled mechanism for refinement of matrix grain size. An analysis of a successful functionally graded composite fabricated by the LENS process is presented. Microstructural features are quantified by X-ray CT, EBSD, and EDS analysis. Mechanical properties are quantified by instrumented micro-indentation, quasi-static mechanical tests. Results demonstrate the range of flexibility within the titanium and boron system to implement functionally graded structures and establish a prototype for exploring new candidates for functionally graded material systems.
A Highly Fracture and Fatigue Resistant Optimized As-deposited EBM Ti-6Al-4V: Mohsen Seifi1; Jesse Boyer2; William Brindley2; John Lewandowski1; 1Case Western Reserve University; 2Pratt & Whitney
The fatigue behavior and damage tolerance of additively manufactured (AM) materials must be assessed and understood in order to utilize them in structural applications. Titanium alloys are of particular interest to the aerospace and biomedical community. While microstructure evaluations and quasi-static tensile properties of EBM Ti-6Al-4V have been reported, fracture toughness and fatigue crack growth properties are not widely available. In this work, an optimized EBM-processed Ti-6Al-4V has been examined in the as-deposited and post-processed Hot Isostatic Pressed (HIP) conditions. The fracture toughness properties were measured in vertical and horizontal directions using a J-based fracture mechanics approach. A very high fracture toughness with some cases of an extended R-curve were obtained before any post-processing. As-deposited fracture and fatigue properties exceeded conventional cast material and approached/exceeded wrought properties. X-ray Tomography studies revealed some level of porosity while optimized HIPping and quenching demonstrated defect elimination and improvement of properties.