Friction Stir Welding and Processing XI: Friction Stir Technologies
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Shaping and Forming Committee
Program Organizers: Yuri Hovanski, Brigham Young University; Piyush Upadhyay, Pacific Northwest National Laboratory; Yutaka Sato, Tohoku University; Nilesh Kumar, University of Alabama, Tuscaloosa; Anton Naumov, Peter The Great St. Petersburg Polytechnic University

Tuesday 8:30 AM
March 16, 2021
Room: RM 39
Location: TMS2021 Virtual

8:30 AM
Effect of Die Geometry on Rate-controlled Friction Extrusion: Xiao Li¹; Md. Reza-E-Rabby¹; Lei Li¹; Ayoub Soulami¹; Glenn Grant¹; Anthony Reynolds²; ¹Pacific Northwest National Laboratory; ²University of South Carolina
     Friction extrusion is a solid phase processing that produces metal and alloy wires with refined microstructure and improved mechanical properties. Like friction stir welding and processing, plastic deformation is produced near the interface between the rotating die and the material being extruded. It is believed that tool surface features may play a critical role in the details of heat generation and material flow. However, the effect of die face feature, like scrolls in comparison to flat featureless dies, has not been systematically studied. In this research, scroll dies and flat dies are employed in rate-controlled friction extrusion. A marker insert technique was used to visualize material flow and calculate the strain in wire. The differences in extrusion force, temperature, torque, power, and strain in the wire are compared and discussed relative to the varied die geometry. Smoothed particle hydrodynamics model was applied to simulate the process and explain results.

8:50 AM
Engineered Metal Matrix Composites Produced Via Co-extrusion for High-temperature Friction Stir Welding: Paul Brune¹; Greg Hilmas¹; Jeremy Watts¹; ¹Missouri University of Science and Technology
    Metal matrix composites are used in the tooling and mining industries for their hardness, fracture toughness, and wear resistance. Research at Missouri S&T is focused on improving the performance of tools used in friction stir welding (FSW) of steels, by employing co-extrusion to produce novel tools with engineered architectures. Co-extrusion offers a way to fabricate hierarchical architectures in composites, by co-extruding a core of one material (e.g., a ceramic) and a shell of a second material (e.g., a metal). Compositions being investigated consist of the following [core]-(shell) combinations: [WC/Co] – (Co), [WC/cBN/Co] – (Co), and [TiB2/SiC/B4C] – (W/Mo). The mechanical properties of each composition were evaluated for viability in FSW, including: flexural strength, hardness, wear resistance, and fracture toughness. Flexural strength and fracture toughness were also evaluated between 900°C and 1200°C in Ar atmosphere. Cylindrical pin FSW tools were machined and tested using both spot and linear welding methods.

9:10 AM
Residual Stresses and Nanoscale Evolution in AA6061 Produced by Additive Friction Stir-deposition: Luke Brewer¹; Ning Zhu¹; Dustin Avery¹; Paul Allison¹; James Jordon¹; Yan Chen²; Ke An²; ¹University of Alabama; ²Oak Ridge National Laboratory
    This presentation will discuss the first neutron diffraction study of an aluminum alloy produced by the additive friction stir-deposition (AFS-D) technique. Friction stir-related processes can generate considerable residual stresses, and this study aims to characterize the level and spatial distribution of these stresses in key locations. Neutron diffraction using the VULCAN beam line at the Spallation Neutron Source was successfully used to measure the distribution of residual stresses. The in-plane residual stresses were slightly compressive at the top of the build surface, close to zero in the bulk of the build, and were tensile in the substrate. As the tool translation speed increased, the magnitude of the residual stresses increased. These measurements also showed a clear shift in the d-spacing of the aluminum matrix in stress-free specimens, indicating that the nanostructure of the material is evolving as a function of position in the build and with tool translation velocity.

9:30 AM
Additive Friction Stir Deposition for Repair and Cladding Applications: Hang Yu¹; ¹Virginia Polytechnic Institute and State University
    Additive friction stir deposition is an innovative additive manufacturing technology that integrates the friction stir principle with material feeding. In this talk, I discuss its applications for the repair of aerospace aluminum plates and selective cladding on automotive aluminum sheet metals. In additive repair, this process enables complete filling of through-holes or grooves in Ľ” plates. Significant material mixing is observed across the interface due to the co-plastic deformation of the sidewall and deposited material, which is continuously compressed and sheared with the arrival of the newly supplied material. In cladding on thin substrates of 1.4 mm thick, this process enables high-quality cladding without interface/surface defects or damage to the substrates. Based on the curvature measurement of the substrate distortion, the residual stress and mismatch strain caused by thermal gradients are estimated. Thanks to the solid-state nature, the estimated values are low, well below the elastic limit of the material.