Additive Manufacturing: Beyond the Beam III: On-Demand Oral Presentations
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee, TMS: Additive Manufacturing Committee
Program Organizers: Brady Butler, US Army Research Laboratory; Peeyush Nandwana, Oak Ridge National Laboratory; James Paramore, US Army Research Laboratory; Nihan Tuncer, Desktop Metal; Markus Chmielus, University of Pittsburgh; Paul Prichard, Kennametal Inc.

Monday 8:00 AM
March 14, 2022
Room: Additive Technologies
Location: On-Demand Room

A Multi-step Data Driven Model for Reverse Shape Compensation for Binder Jet Parts: Hao Deng1; Basil Paudel1; Albert To1; 1University of Pittsburgh
    The large shrinkage of binder jet parts happens during the sintering process, which is used to solidify the object. This sintering distortion may result in unacceptable parts with low geometric accuracy. This work proposes an approach to compensate input geometry files based on simulations using data-driven method. A multi-step neural network approach is proposed for the first time to learn the deformation pattern and compensate the sintering deformation of an initial part geometry. Several initial geometries with different reverse scaling factors are generated and simulated to generate training database. Once the training dataset obtained, a reduced order modeling technique is applied to effectively extract the features of training dataset. A multi-step neural network model is trained and used to predict the compensated part. Finally, the compensated geometry file is validated by building parts and comparing the change in the part distortion.

Microstructure and Mechanical Properties of Friction Stir Deposited SS304: Nikhil Gotawala1; Neeraj Mishra1; Amber Shrivastava1; 1Indian Institute of Technology Bombay
    The objective of this work is to analyse the microstructure and its effect on mechanical properties of friction stir deposited SS304. Friction stir deposition is a solid state additive manufacturing technique, where the material does not melt during the process. This process has shown potential for applications like large scale repairing of steel infrastructure. In this work, friction stir deposition of SS304 is performed at 2000 rpm rotation speed, 1.5 mm/s plunge feed rate and 4 mm/s forward feed rate. The results suggest that a layer of 0.3 mm to 0.4 mm is deposited per pass. The dynamic recrystallization occurred during friction stir deposition, which led to refined microstructure in the deposited region. A bimodal microstructure is observed in the deposited region, with finer grains near the interface of the successive layers. The tensile testing results show that the refinement of microstructure in the deposited region enhances the tensile strength.

Friction and Gravity Effects during Sintering of Binder Jet Parts: Basil Paudel1; Albert To1; 1University of Pittsburgh
    During sintering of binder jet printed parts, distortion is seen with shrinkage values in the range of ~5-20%. External forces such as friction and gravity further contribute towards anisotropy in the deformation behavior. The geometry and complexity of the part combined with the sintering stress and high temperature creep makes prediction of the final part geometry more difficult, thus hindering its wide adoption in the industry. In the present study, a viscoplastic constitutive model is adopted to predict the distortion during sintering of the stainless steel 316L BJP parts. The effects of friction and gravity during high temperature sintering process are analyzed via numerical simulation of a unique test coupon. A model to predict coefficient of friction is proposed. Simulation results indicate close agreement against the experimental observation of friction induced distortion.

Optimization of Al 6061 Powder Feedstock for Cold Spray Using a Through-process Experimental Approach: Kyle Tsaknopoulos1; Bryer Sousa1; Jack Grubbs1; Christopher Massar1; Matthew Gleason1; Danielle Cote1; 1Worcester Polytechnic Institute
    This work employs a Through Process Experiment (TPE) systematic approach to study the relationship between powder properties, cold spray (CS) processing parameters, and consolidated specimen behavior through a combination of characterization and computational models. This TPE approach allows for the systematic isolation of variables that can affect powder and CS properties. In this study, various heat treatments were applied to Al 6061 powder and used as CS feedstock using industry-standard processing parameters to study the effect of thermal pre-treatment of Al 6061 powder on cold spray properties. Techniques including SEM, EDS, XRD, nanoindentation and particle compression, tensile and indentation plastometry testing, corrosion testing, and fatigue testing were used to characterize the properties of both the feedstock powder and CS deposits. Computational thermodynamic modeling was used to guide microstructural interpretation. An additive yield strength model was employed to quantify the strengthening components introduced through the CS process.

X-ray Computed Tomographic Study of Density Gradients within Binder Jet Printed H13 Components: Dustin Gilmer1; Peeyush Nandwana2; Ryan Dehoff2; Tomonori Saito1; 1University of Tennessee Knoxville/Oak Ridge National Laboratory Bredesen Center; 2Oak Ridge National Laboratory
    Binder Jet Additive Manufacturing (BJAM) is a versatile powder bed technique that uses a binder to form complex components. BJAM is well suited for manufacturing at scale due to its high production rates and high resolution. It has been reported that binder-particle interactions during the deposition process result in powder particles being ejected from the powder bed. However, the impact of these ejected particles on the bulk part is not well understood. We use x-ray computed tomography to study this in H13 steel parts as printed in the green state, as well as how it subsequently impacts the debinding and sintering behavior of the material. This information will be critical for understanding the evolution of defects in sintered components and their role on material properties as well as provide insights towards sintering kinetics of H13.