Additive Manufacturing: Beyond the Beam II: Deformation Based Processing
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee, TMS: Additive Manufacturing Committee
Program Organizers: Paul Prichard, Kennametal Inc.; James Paramore, Texas A&M University; Peeyush Nandwana, Oak Ridge National Laboratory; Nihan Tuncer, Desktop Metal
Thursday 8:30 AM
March 18, 2021
Room: RM 4
Location: TMS2021 Virtual
Session Chair: James Paramore, Texas A&M University
8:30 AM
In Situ Monitoring of Additive Friction Stir Deposition: An Overview: Hang Yu1; 1Virginia Polytechnic Institute and State University
Additive friction stir deposition is a newly-developed solid-state additive process that enables freeform metal fabrication by integrating the friction stir principle with material feeding. While it holds the promise of achieving refined, equiaxed microstructures and excellent mechanical properties in the as-printed state, the process fundamentals have remained elusive. In this talk, I will give an overview of the in situ monitoring strategies for additive friction stir deposition, with the aim to better understand the temperature evolution, force/torque evolution, interface contact, and the material flow behavior. From these studies, empirical relationships are established between the peak temperature and processing parameters, while various force and torque regimes are determined for the plunge and deposition phases. Moreover, a comparative study of printing Al and Cu provides new insights into the role of intrinsic material properties, such as forgeability and friction coefficient, in heat generation and plastic deformation during the process.
8:50 AM
Texture Development and Influence in Solid-state Additive Manufacturing: Robert Griffiths1; Mackenzie Perry1; David Garcia1; Hang Yu1; 1Virginia Polytechnic Institute
Among the difficulties in using beam-based additive manufacturing (AM) processes, is the tendency for materials to form columnar grain structures during repeated melting and solidification, resulting in strong textures and anisotropy. While numerous advances have been made in material composition and beam rastering strategies, solid-state AM avoids this columnar growth with no special precautions. Although epitaxial growth is largely avoided, texture and the resulting anisotropy must still be considered for solid-state AM techniques. Here we discuss texture evolution and control in the solid-state process, Additive Friction Stir Deposition (AFSD). The asymmetric deformation during material deposition with AFSD is generally found to produce shear textures, of which the orientation, magnitude, and influence on properties changes with material and process parameters. The wide process window in which AFSD operates is found to enable a degree of control over such features, and their implications are discussed.
9:10 AM
Complex Material Deformation and Flow Phenomena during Additive Friction Stir Deposition of Dissimilar Aluminum Alloys: Mackenzie Perry1; Hunter Rauch1; Robert Griffiths1; Jennifer Sietins2; Yunhui Zhu1; David Garcia1; Hang Yu1; 1Virginia Tech; 2CCDC Army Research Laboratory
Additive friction stir deposition (AFSD) is an innovative metal additive manufacturing technology based on high-temperature severe plastic deformation that enables solid-state deposition. By simultaneous rotation and compression of the feed material through a tool, large-scale parts are deposited with strong interface bonding, no detectable porosity, and an isotropic, fine grained microstructure. A fundamental understanding of the complex material deformation and flow phenomena during AFSD is essential to further optimize this process. In this work, experiments using hybrid feed-rods composed of tracers and matrix are used to explore the material flow within the deposition zone. X-ray computed tomography and electron backscatter diffraction show the complex 3-D shape of the deposited material and the microstructure evolution. Tracer cores show that the material flow path is dependent on placement within the feed-rod and processing parameters. The shape change between neighboring tracer segments reveals the first estimation of strain and strain rate in AFSD.
9:30 AM
Friction Stir Additive Manufacturing of Al 6061-T6: Modeling and Experimental Analysis: Nitin Rohatgi1; Yung Shin1; 1Purdue University
Solid state additive manufacturing techniques are used to overcome the disadvantages of fusion based additive manufacturing. Friction stir additive manufacturing (FSAM) holds promise in this this regard with improved microstructure and structural performance. This study investigates the microstructure and mechanical properties of Al6061-T6 prepared by FSAM, and employs a Coupled-Eulerian Lagrangian finite element model to predict the tool reaction forces, stresses, and temperature distribution, which is used to predict the process parameters for a sound weld. The model also predicted the temperature history of the plates, based on which the microhardness of the material is predicted. Based on modeling and experiments, the quality of the material fabricated is investigated in terms of process parameters. Tensile tests were conducted in the transverse direction to observe the strength and ductility. The microstructure of the processed part is studied and used to explain the behavior of the material.
9:50 AM
Cold Spray Processing of Soft Metals and Hard Tool Steels: Yu Zou1; 1University of Toronto
Cold spray, initially a coating technique, is being touted as a ‘near-net shape’ manufacturing technology that minimizes material waste by virtue of the high rate of deposition. During the cold spray process, metallic bulk components can be produced by spraying metal powders at high velocity, generating bonding through severe plastic deformation at temperatures well below the melting point of the powders. To fully understand the cold spray processing of metal powders, we systematically compare and study the microstructure evolution in Cu, Ni, Al, Ti, tool steels prepared by cold spray. We show complex microstructure in these powder particles after cold spraying: nanocrystalline, nanotwins, annealing twins, gradient grains, deformation bands, dynamic/static recovery and recrystallization. The effects of gas temperature and powder velocity on the microstructure and mechanical properties in the cold sprayed samples are also discussed. Of particular interest are grain refinement, recrystallization and particle/particle bonding mechanisms of the powder particles.
10:10 AM
Heat Treatment of Recycled Battlefield Stainless-Steel Scrap for Cold Spray Applications: Christopher Massar1; Kyle Tsaknopoulos1; Bryer Sousa1; Jack Grubbs1; Danielle Cote1; 1Worcester Polytechnic Institute
This work explores the preprocessing of recycled austenitic stainless-steel powder for solid-state cold spray metal additive manufacturing. This work aimed to increase deposition quality and coating density while maintaining mechanical integrity. The recycled stainless-steel scrap was gas-atomized using a novel mobile foundry manufactured by MolyWorks Materials Corporation. The powder was thermally treated based upon thermodynamic modeling using Thermo-Calc. The powder and sprayed specimens were characterized using particle size–shape analysis, microscopy, x-ray diffraction, and nanoindentation. Diffraction results highlighted the presence of both austenite and ferrite phases in the powder. Nanoindentation confirmed that thermally processing the feedstock powder at the austenitization temperature decreased the amount of ferrite present, which was consistent with the porosity observed in the deposits due to the lower yield strength of austenite relative to ferrite. The untreated powder deposits exhibited extensive porosity and microcracking, as opposed to the virtually fully dense deposit from the heat-treated powder.
10:30 AM
Understanding the Effects of Repeated Environmental Exposure on Powder Properties for Additive Manufacturing Applications: Jack Grubbs1; Aaron Birt2; Aaron Nardi3; Danielle Cote1; 1Worcester Polytechnic Institute; 2Solvus Global; 3Army Research Lab
Metal powder-based additive manufacturing (AM) processes have seen increased use in academia, government, and industry over the past decade. Often, the success of these processes is contingent on the quality of the feedstock powder used. This dependency is even greater for solid-state AM processes such as cold spray (CS). The CS process greatly relies on adequate control of powder flowability and moisture content in order to maintain predictable through-process powder behavior. However, frequently during handling, the metallic powder is repeatedly exposed to ambient conditions, which has the potential to degrade powder properties. To avoid compromising the future success of the CS process, it is critical to understand how this environmental exposure during powder handling can affect the feedstock's properties. It is the aim of this study to evaluate the effects of repeated environmental exposure on the flowability and moisture content of aluminum alloy powders for CS applications.
10:50 AM
Aluminum Alloy Powders for Solid State Additive Manufacturing Processing: Kyle Tsaknopoulos1; Jack Grubbs1; Danielle Cote1; 1Worcester Polytechnic Institute
With the rise of additive manufacturing (AM), research about new and old alloy compositions to be used for these processes is becoming more prevalent. In an effort to determine if these alloys are also advantageous to use for non-traditional AM processes, such as the solid-state cold spray process, research was conducted using various AM alloys as feedstock. As powder properties are a function of their internal microstructure, it is therefore important to understand the microstructure in order to optimize the properties of the final parts. Powder properties can be controlled through the use of thermal treatment and analyzed through microstructural evolution. Heat treated AM powder was also tested as feedstock for the cold spray process. The internal microstructure of the feedstock powder was analyzed using scanning electron microscopy, energy dispersive x-ray spectroscopy, and nanoindentation and guided through the use of computational thermodynamic and kinetic models. Mechanical properties were also determined.
11:10 AM
Linear Friction Welding: a Solid-state Joining Process for the Manufacturing of Aerospace Titanium Parts: Nicolas Piolle1; 1ACB
Linear Friction Welding (LFW) is a solid-state joining process offering new opportunities of cost reduction and quality improvement for aerospace titanium part manufacturing. The process produces in a few seconds high integrity joints with fine grain, hot-forged microstructure and narrow heat affected zone. The LFW process reached a high enough level of maturity, robustness and reliability to be ready for mass production of blisks (“blade disks”) for aircraft engines. It is now being developed for aircraft structural parts in aluminum and titanium alloys. This process allows not only to manufacture a given part at a lower cost, it also opens new part design possibilities that were not available with traditional manufacturing processes. The LFW process is explained through physical aspects, process parameters, mechanical characterization of the joint and microstructural data. Several LFW aerospace applications are introduced and evaluated through feasibility, weight reduction, post-weld operations and overall cost savings.