Friction Stir Welding and Processing XI: High Melting Temperature Materials
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
Monday 2:00 PM
March 15, 2021
Room: RM 39
Location: TMS2021 Virtual
2:00 PM
Study of Residual Stress and Microstructure Changes in Friction Stir Processed Dual Phase 980 Grade Steel: Koichi Taniguchi1; Yong Chae Lim2; Jeffery Bunn2; Zhili Feng2; 1JFE Steel Corporation; 2Oak Ridge National Laboratory
Friction stir processing is a unique solid-state process to change microstructures and their mechanical properties by extensive shear and plastic deformation. The complex microstructure evolutions, such as texture changes, dynamic recrystallization and grain refinement, transiently occur due to the compressive and shear loading in elevated temperature during the process. In present work, we employed a pin-less friction stir processing on advance high strength steel (i.e., dual phase 980MPa grade steel) with different processing conditions. Different peak temperatures under different processing conditions were measured by thermocouples and infrared camera. Friction stir processed steel samples were characterized by optical and electron microscopies, microhardness measurement, and residual stress measured by neutron beam at Oak Ridge National Laboratory to study quantitative stress state and correlation to microstructure evolutions under various processing conditions.
2:20 PM
Advances in High Temperature FSW: Single Use Tools: Jonathan Peter Martin1; 1TWI Ltd.
FSW has become well established for the fabrication of aluminium and other light metals over the thirty year period since its invention. The demonstrated benefits of the process, not only in terms of weld quality but also the ability to introduce automation and enhance the health and safety aspects of welding, have long led to a desire to utilise FSW for welding high plasticisation point metals such as nickel, titanium and steel. These developments have been held back in many cases by the difficulty in finding a suitable and reliable tool able to withstand the welding environment and be commercially viable. TWI has approached this problem by developing a tooling system incorporating a low cost, single use, replaceable insert. This presentation describes this motivation behind this development, tool performance and weld properties when welding Ti6Al4V plates.
2:40 PM
Phosphorus Segregation and Its Effect on Properties in Friction Stir Welded High Phosphorus Weathering Steel: Takumi Kawakubo1; Kohsaku Ushioda1; Hidetoshi Fujii1; 1Joining and Welding Research Institute Osaka University
Phosphorus (P) addition is expected to simultaneously increase the strength and corrosion resistance of weathering steels but causes solidification cracking during the fusion welding process. To avoid this problem, the added P content is currently limited. Friction stir welding (FSW), which is a solid-state joining process, can overcome the problem with weldability in the fusion welding process. On the other hand, the high P concentration causes the P segregation to the grain boundaries besides the solidification segregation, possibly leading to reduce toughness. In this study, high P weathering steel was prepared and FSW was performed at temperatures below A1 and above A3. For the base pearlite steel material and the stir zones, the P segregation and its effect on toughness were investigated in detail and the mechanism behind was discussed focusing on the effect of grain size on grain boundary segregation and toughness.
3:00 PM
Friction Stir Welding of Armor Grade Steels: Stan Hawkes1; Rafael Giorjao1; Martin McDonnell2; Antonio Ramirez1; Alex Thiel3; Michael Eff4; 1Ohio State University; 2US Army; 3Oshkosh Corp.; 4EWI
For years, the defense industry has been driven to make their armored combat vehicles lighter without compromising its security. Friction Stir Welding (FSW) has been identified as an avenue to promote this objective. Under the proper circumstances, the FSW process can produce sound welds that do not require extra armor to protect a degraded and vulnerable heat-affected zone (HAZ), as observed in traditional arc welding. This work presents the exploration of advanced process control and pre/post-heating during FSW of armor steels to optimize microstructure and joint performance, with emphasis on toughness improvement.
3:20 PM
Friction Stir Welding of NiTi Shape Memory Alloy: Parker West1; Vasanth Shunmugasamy2; Bilal Mansoor; Ibrahim Karaman1; 1Texas A&M University; 2Texas A&M University at Qatar
In the present work, we have utilized friction stir welding (FSW) to weld equiatomic NiTi shape memory alloy (SMA). Since FSW is a solid-state joining process, usual drawback associated with fusion joining process is eliminated. A successful joint was prepared on equiatomic NiTi SMAs using FSW and microstructure analysis showed a defect free joint along with absence of thermomechanically affected (TMAZ) and heat affected zones (HAZ) in the weld macrostructure. Transformation temperatures measured in the stir zone using differential scanning calorimetry showed very little changes when compared with base material. Vickers microhardness characterization showed consistent hardness values across the weld joint. Tensile testing of the weld coupons showed a maximum joint efficiency of 93% in martensitic phase and a joint efficiency of 84% in austenitic phase tested at elevated temperature. Results from the present work suggest than FSW can be successfully applied to join NiTi SMAs.
3:40 PM
On the Development of Friction Stir Welding to Repair or Mitigate Chloride-induced Corrosion in 304L Austenitic Stainless Steel: Benjamin Sutton1; Gabriella Marino1; Rafael Giorjao1; Jayendran Srinivasan1; Antonio Ramirez1; Jenifer Locke1; 1Ohio State University
Friction stir welding (FSW) has been proposed as a repair or mitigation process for austenitic stainless steel structures that experience chloride-induced corrosion. The feasibility of using FSW to repair such structures has been demonstrated, however limited information has been published regarding the effect of FSW process parameters on subsequent corrosion performance. A study has been conducted to assess the effects of FSW process conditions on 304L austenitic stainless steel weldment properties. Simulations were performed to support thermal analysis of the FSW process using process parameters and material constitutive data. Optical and scanning electron microscopy were used to evaluate defect formation and microstructure evolution. Localized mechanical properties were assessed using indentation techniques. Corrosion performance was evaluated using electrochemical polarization and boiling magnesium chloride testing. The resulting corrosion behavior will be compared to as-received base material, furnace sensitized base material, and gas tungsten arc weldments.
4:00 PM
Low-force Friction Surfacing for Crack Repair in 304L Stainless Steel: Hemant Agiwal1; Hwasung Yeom1; Kumar Sridharan1; Kenneth Ross2; Frank Pfefferkorn1; 1University of Wisconsin-Madison; 2Pacific Northwest National Laboratory
The objective of this research is to evaluate low-force friction surfacing as a means for repairing cracks in 304L stainless steel canisters. The motivation for reducing process forces is to allow for portability of the system to perform in-field repairs. 304L austenitic stainless-steel rod was deposited over a substrate of the same alloy using a CNC machine tool in position control mode while observing the process forces, spindle torque, and temperature on the back side of the repair. Friction surfacing was performed at spindle speeds up to 20,000 RPM. A fine grain structure with some martensitic transformation was observed in the plastically deformed material. Friction surfacing was performed on simulated cracks followed by helium leak testing to evaluate the ability to create a gas-tight repair. Closing of cracks near the interface of substrate and deposit was observed after microstructural analyses.
4:20 PM
Evaluation of Residual Stresses in Isothermal Friction Stir Welded 304L Stainless Steel Plates: Madhumanti Bhattacharyya1; Thomas-Gnaupel Herold2; Krishnan Raja1; Jens Darsell3; Saumyadeep Jana3; Indrajit Charit1; 1University of Idaho; 2National Institute of Standards and Technology; 3Pacific Northwest National Laboratory
Friction stir welding was performed on 304L SS plates to heal simulated cracks (created by electrical discharge machining) at two different tool temperatures (825 and 725°C). Both neutron diffraction and X-ray diffraction techniques were employed to measure the weld residual stresses along two orthogonal reference directions, longitudinal (σxx) and transverse (σyy). It was found that, at 1 mm depth from the top surface inside the stir zone (SZ), the longitudinal component was tensile in nature while the transverse component was compressive. The nature and values of the residual stress fields, and the position of the peak residual stresses were found to vary with the weld depth. The SZ of the 725°C weld exhibited higher peak stress than 825°C weld mainly due to a lack of stress relief at the lower temperature. The work is supported by US DOE Office of Nuclear Energy’s Nuclear Energy University Program.