Friction Stir Welding and Processing XI: Dissimilar
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
Wednesday 8:30 AM
March 17, 2021
Room: RM 39
Location: TMS2021 Virtual
8:30 AM Invited
Friction Stir Welding of Metal and Carbon Fiber Reinforced Plastic: Hidetoshi Fujii1; Jeong-Won Choi1; Yoshiaki Morisada1; Kimiaki Nagatsuka1; Kazuhiro Nakata1; 1Osaka University
In order to incorporate the advantage of each material and complement for each drawback, the friction stir welding of metallic and non-metallic materials is one of the important next targets. Carbon Fiber Reinforced Plastic (CFRP) have been widely used in the fields of engineering and industries due to their outstanding characteristics such as high specific strength. In this study, the friction stir welding of Ti alloys and CFRP (polyamide 6 with 20 wt.% carbon fiber) was investigated to solve the dimensional problem and simultaneously suppress the welding defects formation by the applied pressure from the tool and the easy control of the welding temperature. Before welding, a surface treatment was performed on the Ti surface using a silane coupling agent. The welding parameters including the tool rotation speed were optimized in order to achieve a sound dissimilar joint of Ti and CFRP.
8:50 AM
Friction Stir Welding of Metal Matrix Composites to Dissimilar Aluminum Alloys: Optimization of Weld Quality and Tool Life
: Michael Eff1; Scott Rose2; Kyung Chung3; Don Hashiguchi3; Drew Shipley1; Elizabeth Burns2; 1EWI; 2Boeing; 3Materion
The emergence of metal matrix composites (MMC) offer many advantages for the aerospace industry including high specific stiffness and strength. Joining of MMCs can be very challenging due to their composition. Friction Stir Welding (FSW) can join MMCs, but often experiences severe wear of the tool due to the SiC particles limiting its commercial viability. This work will summarize a development effort to design long life FSW tools and optimize the welding parameters via design of experiment (DOE) techniques in several MMCs for use as stiffener for aerospace panels. Weld quality and the effects of FSW on the MMC/Al joints were examined using lap shear tensile testing, mini-tensile testing, metallographic examination, and scanning electron microscopy. Tool life was examined using repeated bead of plates welding trials in two different MMCs. The study resulted in optimized tool materials and welding parameters for the MMC/Aluminum lap welds.
9:10 AM
Dissimilar Joining of ZEK100 and AA6022 for Automotive Application: Hrishikesh Das1; Piyush Upadhyay1; Woongjo Choi1; Shank Kulkarni1; 1Pacific Northwest National Laboratory
Mg and Al joining is problematic due to different high temperature flow characteristics that often results in weld defects and brittle intermetallic compounds (IMC). We present process development on lap joining of 1.27mm 6022 (top sheet) and 1.5mm ZEK100 (bottom sheet) for an automotive door application. We conducted linear welding using power control mode (modulating torque and spindle speed) with multiple tool designs, and welding parameters. Process variables were correlated to joint micro-structure and mechanical properties. A 2D computational model was created to understand the failure mechanism and contribution of mechanical interlocking towards joint strength. For a thin (< 2mm) automotive sheet with relatively softer material as a bottom sheet, adequate control of process variables is critical to maintain weld stability and avoid excessive IMC layer at the interface. A combination of mechanical anchoring and metallurgical reaction is likely responsible for bonding.
9:30 AM
Fracture Mechanics Approach to Improve Fatigue Strength of a Dissimilar Metal T-Lap Joint by Friction Stir Welding: Masakazu Okazaki1; Hao Duong1; Satoshi Hirano2; 1Nagaoka University of Technology; 2Hitachi Research Laboratory
Friction Stir Welding (FSW) is expected as one of industrial solutions to fabricate high performance dissimilar metal welds consisting of the materials to which normal fusion welding process(es) is (are) hardly applied. However, the strength of FSWed T-lap joint, especially for the fatigue failures, has not been satisfactory so far, due to formation of some undesirable defects in the joint; e.g. tunnel, kissing bond, zigzag line, bonding line, oxide line defects, etc., those directly degraded the mechanical properties of the joint. In this work the fatigue strength of dissimilar metal FSWed T-lap joint between AA7075 and AA5083 was studied, paying attention to the fatigue crack nucleation sites and the morphologies. Some fracture mechanics strategies are proposed to improve the fatigue strength associating with enough rupture ductility.
9:50 AM
Effect of Diffusion on Intermetallics at Interface during Friction Stir Welding of Stainless Steel and Pure Titanium: Nikhil Gotawala1; Amber Shrivastava1; 1Indian Institute of Technology Bombay
Relatively lower temperatures during friction stir welding, limit the formation of intermetallic compounds while joining dissimilar materials. The objective of this work is to understand the intermetallic compound formation and growth during friction stir welding of stainless steel and pure-Ti. Friction stir welding of stainless steel and titanium is performed at two tool rotation speeds: 600 rpm and 700 rpm, with 50 mm/min feed rate and 0.3 mm plunge depth. Numerical modelling is done to predict temperature distribution and history in the stir region. The temperature history is used to estimate the elemental concentration profiles and intermetallic thickness at the interface. Experimental results show FeTi intermetallic at both sides of the interface and β-Ti at titanium side. Further, β-Ti growth rate is higher compared to FeTi growth rate. Numerical results well capture the experimental observations.
10:10 AM
Microstructural and Mechanical Characterization of Titanium/Steel Joints Produced by Ultrasound Enhanced Friction Stir Welding: Andreas Gester1; Marco Thomae1; Guntram Wagner1; 1Chemnitz University of Technology
Superimposing the friction stir welding process with another type of energy input is able to improve the joint quality and tensile strength of FSW joints further. One approach is the transmission of high power ultrasound into the joining zone synchronously to the FSW process through an ultrasound roll seam module. This hybrid method has shown a positive impact on the joints, e.g. an improved stirring in the nugget and the shattering of undesired intermetallic phases, which lead to enhanced mechanical properties. Current work focuses on utilizing this hybrid method for producing joints of Ti6Al4V and SAE 304 sheets. Response surface methodology has been used for identifying suitable process parameters. For comparing the effect of high power ultrasound during the FSW process the microstructure of these joints has been evaluated via light/scanning electron microscopy as well as microhardness mappings. Quasi-static and dynamic properties have been investigated via tensile and fatigue tests.