Additive Manufacturing: Building the Pathway towards Process and Material Qualification: Beam Line Studies and In Situ Monitoring
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

Tuesday 8:30 AM
February 28, 2017
Room: 8
Location: San Diego Convention Ctr

Session Chair: Manyalibo Matthews, Lawrence Livermore National Laboratory; Jason Fox, National Institute of Standards and Technology

8:30 AM  Invited
Process Monitoring for Powder Bed Fusion of Metal Alloys Using High Speed Optical Diagnostics: Manyalibo Matthews1; Gabe Guss1; Nicholas Calta1; Sheldon Wu1; Sonny Ly2; Michael Crumb1; 1Lawrence Livermore National Laboratory; 2LLNL
    Irregularities in melt pool conditions during powder bed fusion (PBF) processing can lead to localized defects and poor part quality. Here we present high speed thermographic and profilometry measurements of melt pool evolution and layer-to-layer height variation during PBF processing. We also discuss the transient behavior related to the interaction between the melt pool, laser beam, and powder bed. We directly observe and quantify important process characteristics such as peak temperatures, temperature gradients, spatter ejection and melt pool oscillations. Our high speed acquisition allows detailed features in the final melt track morphology to be observed and associated with changes in thermal profiles. Along with providing process monitoring data to facilitate part certification, data provided by our diagnostics can help validate process models. The practical implementation of these high speed diagnostics into commercial platforms is also discussed.

9:00 AM  
The Use of Laser Ultrasound to Detect Defects in Laser Melted Parts: Phill Dickens1; Sarah Everton1; Chris Tuck1; Ben Dutton2; David Wimpenny2; 1University of Nottingham; 2MTC
     Additive Manufacturing (AM) offers a number of benefits over conventional manufacturing, giving an increased design freedom and the opportunity to integrate multiple components, saving weight. The rigorous standard for material integrity set by the Aerospace sector necessitates the development of systems to ensure quality.Laser Ultrasonic (LU) testing is a non-contact inspection technique which has been proposed as suitable for in-situ monitoring of AM processes, as measurements can be taken at elevated temperatures. This paper will show the capability of this technique for identifying defects in metal AM parts and compare it with CT scanning.

9:20 AM  
Embedding Fiber Bragg Gratings with Ultrasonic Additive Manufacturing: Adam Hehr1; Mark Norfolk1; 1Fabrisonic LLC
    Recent advancements in 3D printing of metals has enabled metal parts to be produced with functional embedded sensors. Ultrasonic Additive Manufacturing (UAM), a rather new 3D printing technology, uses ultrasonic energy to produce metallurgical bonds between layers of metal foils near room temperature. This low formation temperature enables the integration of temperature sensitive fiber optic Bragg grating strain sensors into metal structures. These structures have broad use for in-situ load and health monitoring, especially in the aerospace field. In addition to creating a self-sensing structure, the in-situ strain imparted on the sensor during embedding can be monitored to improve understanding of the imparted plastic strain of the welding process.

9:40 AM  
The Development of a L-PBF Test Bed and Evaluation of In-process Sensing Technologies: Bryant Foster1; 1EWI
    In-process sensing is a necessity to move from 3D-printing to additive manufacturing. Specifically, there is a need to move from prototyping to manufacturing high quality parts to be used in real designs. To move towards process and material qualification for additively manufactured parts, the laser powder bed fusion (L-PBF) process must be monitored for a variety of defects throughout the building process. EWI has made major progress in this area through the evaluation of multiple state of the art sensors on an open architecture L-PBF Test Bed. Sensors included local, global, and passive devices ranging from thermal melt pool monitors and spectrometers to laser profilometers and acoustic sensors. Sensors were evaluated for their inherent capabilities in detecting build contamination, defects, and process variations of varying magnitudes. Results show that a suite of sensors, rather than a single sensor type, will be required to fully qualify the process in the future.

10:00 AM Break

10:20 AM  Invited
Using Neutron and High Energy X-ray Diffraction to Probe Additively Manufactured Materials Over a Range of Length and Time Scales: Donald Brown1; John Carpenter1; Bjorn Clausen1; Jason Cooley1; John Bernal1; Mark Bourke1; 1Los Alamos National Lab
    This talk will present our efforts to characterize the processing/microstructure/properties/performance relationship of additively manufactured materials across many length and time scales utilizing both neutron and high-energy x-ray scattering techniques. As an example of studying the effect of processing on microstructure, high energy x-ray diffraction has been used to monitor microstructural evolution in-situ during additive manufacture of 304L stainless steel with sub-second time resolution and sub 0.1mm spatial resolution. Specifically, the evolution of phase fractions, liquid and multiple solid phases, is monitored immediately following deposition. On larger time and length scales, neutron diffraction has been used to monitor microstructural evolution in-situ during post-deposition heat treatment of stainless steel, an integral part of metal additive manufacture. The study is extended to include the linkage of processing to properties through in-situ neutron diffraction measurements during deformation of additively manufactured materials.

10:50 AM  
Residual Stress Characterization of Additively Manufactured Components: Maria Strantza1; Danny Van Hemelrijck1; Patrick Guillaume1; 1Vrije Universiteit Brussel
    Additive manufacturing (AM) should be tailored to the needs of the industrial sectors. In order to exploit the major advantages of AM in real life applications, a better understanding of the phenomena taking place during AM process is crucial. During the production of an AM component, high thermal gradients cannot be avoided. The material’s thermal gradients are complex due to the layer by layer nature of the process and is inevitable resulting in a complex residual stress distribution. Having knowledge about the magnitude and distribution of the residual stresses is important and there are many techniques that are used in order to characterize them. The aim of this work is to study the effect of the residual stresses in additively manufactured components by means of neutron diffraction and incremental centre hole drilling methods. The effect of the residual stresses in fatigue was also investigated in as-built and stress relieved conditions.

11:10 AM  
In Situ Observation of Porosity Formation in Selective Laser Melting Using Synchrotron-based High Speed X-ray Imaging: Ross Cunningham1; Robert Suter1; Anthony Rollett1; Jack Beuth1; 1Carnegie Mellon University
    Additive manufacturing provides the means to fabricate complex metallic parts with reduced time to market and material waste. However, while most mechanical properties of AM parts can meet or exceed those of conventionally manufactured materials, fatigue resistance has been consistently inferior due to the large and highly variable presence of porosity in the parts. This presents a challenge for part qualification for any critical or load bearing part without extensive post-processing and part inspection. Previous work by the authors and others have shown strong circumstantial evidence of porosity transference from the powder, but many porosity formation mechanisms in SLM parts require further investigation to validate current models. This work uses newly developed capabilities at Argonne National Lab's Advanced Photon Source to observe porosity developing in the melt pool during processing using high speed X-ray imaging and 3D X-ray microtomography.

11:30 AM  
Characterizing Microstructure in Ti Alloys Using Synchrotron-based MicroCT: Johanna Weker1; Ryan Ott2; Yinmin Wang3; Kevin Stone1; Chris Tassone1; Matthew Kramer4; Tony Van Buuren3; Michael Toney1; 1SLAC National Accelerator Laboratory; 2AMES; 3Lawrence Livermore National Laboratory; 4AMES Laboratory
    Additive manufacturing promises to initiate a renaissance in American manufacturing by decreasing costs, increasing energy efficiency, enabling new component design motifs, and providing a manufacturing pathway for novel materials which cannot be processed by traditional means. However, fabrication processing parameters need to be tied to specific microstructure which ultimately determine the performance of machined parts. Using X-ray micro computed tomography (micro-CT) at the Stanford Synchrotron Radiation Lightsource at SLAC National Accelerator Laboratory, we have nondestructively screened the 3D microstructure of Ti alloy components manufactured under various processing conditions. With micro-CT we can measure parameters such as void size, distributions, morphology, and rate of occurrence. These experimental results can be utilized to validate and improve existing models to predict microstructure.