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

Thursday 8:30 AM
March 23, 2023
Room: 29A
Location: SDCC

Session Chair: Piyush Upadhyay, Pacific Northwest National Laboratory; Xiao Li, Pacific Northwest National Laboratory


8:30 AM  Invited
High Speed Butt Joining of 1" Thick 2139-T8: Hrishikesh Das1; Piyush Upadhyay1; Reza Rabby1; Uchechi Okeke2; Martin McDonnell2; 1Pacific Northwest National Laboratory; 2DEVCOM GVSC
    Thick plate (≤1”) butt joining of Al alloys is challenging due to high tool forces, uneven material flow, and heat distribution in the through-thickness direction. Tool design and welding parameters used to execute thick plate butt joining have remained mostly static over the past decade. Reported welding speeds that produce viable joint strength (mostly on 6xxx alloys) typically range below 100 mm/min (4inches /min). Researchers at Pacific Northwest National Laboratory (PNNL) in association with Ground Vehicle Systems Center (US Army GVSC) have been working to demonstrate greater joining efficiency at higher welding speeds in 1” thick AA2139-T8 plate. Using innovative tool features and effective force and temperature control a joint efficiency of 80% was demonstrated at a welding speed of 7 inches /min (178mm/min).

8:50 AM  Invited
Friction Stir Welding to Seal 5 cm Thick Copper Canisters Containing Sweden´s Nuclear Waste: Lars Cederqvist1; 1Swedish Nuclear Fuel and Waste Management Company (SKB)
    SKB has chosen FSW to seal the copper canisters that will contain Sweden´s nuclear waste. This paper shows the results and the challenges in this development as it approaches qualification and production. The major challenges include repeatable probe manufacturing and control and measurement of the shoulder depth. By controlling the shoulder depth the possible hook discontinuity in the capture joint can be controlled.

9:10 AM  Invited
Joining Cast Mg AZ91 and Wrought Al 6082 through Friction Stir Welding: Krzysztof Mroczka1; Stanisław Dymek2; Adam Pietras3; Aleksandra Węglowska3; Carter Hamilton4; Mateusz Kopyściański2; 1Cracow University of Technology; 2AGH University of Science and Technology; 3The Łukasiewicz Research Network Institute of Welding; 4Miami University
    Dissimilar welds of cast AZ91 with wrought aluminum 6082 were fabricated by friction stir welding (6 mm thick) with the alloys alternately placed on the advancing and retreating sides. The unique weld microstructures were characterized through light and electron microscopies (SEM-EBSD, TEM), tensile tests were performed on samples containing the entire welds and the microhardness was measured across the weld cross-sections. Supplementing the conventional tensile tests, micro tensile specimens (cross-sectional area of 0.7 x 0.7 mm) were excised by wire EDM from the specific areas of the weld to highlight differences in local properties that influence weld behavior. Preliminary results demonstrate that some regions contain a significant amount of the brittle Al12Mg17 phase. To complement the microstructural and mechanical characterization, numerical simulations of the welding process provided deeper insight into the material flow during mixing and to the temperature distributions across the weld zones.

9:30 AM  Invited
Dissimilar Copper and Aluminium Joining Using a Solid-state Friction-stir Welding Process: Nishkarsh Srivastava1; Arpan Rout1; Amit Arora1; 1Indian Institute of Technology Gandhinagar
    The dissimilar fusion welding of aluminium and copper is challenging due to the differences in chemical, mechanical and thermal properties. Friction stir welding (FSW) is one of the alternatives being capable of joining dissimilar metals without affecting the mechanical properties of metals. In this work, the mixing behaviour of Al and Cu is studied by characterizing successfully joined 5083 and 6061 aluminium alloys with copper using FSW. In addition, the effect of changing shoulder diameter is analyzed on the intermetallic formation of Cu-Al dissimilar weld. The grain morphology at the interface is studied at the weld interface using the scanning electron microscopy (SEM) - electron backscatter diffraction (EBSD) technique. The intermetallic compound formation influences the hardness in the stir zone with a higher shoulder diameter resulting in increased intermetallic formation. The SEM studies of fractured specimens indicated a ductile and brittle mixed fracture.

9:50 AM Break

10:10 AM  
Copper-aluminum Hybrid Induction Motor Rotors Using Friction Stir Welding: Hrishikesh Das1; Piyush Upadhyay1; Glenn Grant1; John Agapiou2; Blair Carlson2; 1Pacific Northwest National Laboratory; 2General Motors
    Replacement of copper end caps with Aluminum in rotor design has the potential to make induction motors lighter and cost-effective for EV applications. However, Al-Cu die casting is challenging. In a collaborative project, Friction stir welding is being evaluated as a viable method to produce a robust Al-Cu interface without the need for die casting. In this work, the copper shorting bars are perpendicular to the end cap and the end caps are made of multiple stacks of Al. Novel Al-Cu interface geometries/tool designs were developed to produce various Al-Cu bonded joints in a linear coupon scale. Several FSW strategies including single pass, 2 pass and 3 pass with a few tool designs have been evaluated. It was found that double pass friction stir welding provided excellent tensile strength with small variability. SEM/EDS analysis revealed a submicron level intermetallic layer at the Al-Cu interface.

10:30 AM  
Mechanism of Joint Formation in Dissimilar Friction Stir Welding of Aluminum to Steel: Amlan Kar1; Todd Curtis1; Bharat Jasthi1; Grant Crawford1; 1Arbegast Materials Processing and Joining Laboratory (AMP),
    This paper highlights the influence of load-controlled experiments on heat input and corresponding improvement in mechanical properties of dissimilar friction stir lap welding (FSLW) of aluminum 6061 alloy (Al) and low carbon steel (Fe) with different thicknesses. Dissimilar welds are produced at different loads and heat input conditions. The microstructure and chemical composition of the weld interface was characterized to determine the grain morphology, deformation behavior, intermetallics compounds formation and joining mechanisms at the aluminum to steel interface. An improvement (more than 60% joint efficiency) in shear tensile properties were reported under optimized process conditions. Mechanisms associated with improved tensile properties have been identified. Mechanical mixing, formation of an intercalated structure with a reduction in intermetallic compounds, and grain refinement are considered the mechanism of dissimilar joint formation.