7 Journal of Environmental Friendly Materials, Vol. 2, No. 1, 2018, 7-12. Effect of the FSW Tool Pin Profile on Mechanical Properties of the Al6061-Cu Plates Joint F. Khalili 1 , K. Amini 1,2,* , M. Golzar Shahri 1 , F. Gharavi 3 1 Advanced Materials Research Center, Department of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran 2 Department of Mechanical Engineering, Tiran Branch, Islamic Azad University, Isfahan, Iran 3 Department of Materials Engineering, Sirjan Branch, Islamic Azad University, Sirjan, Iran Received: 12 October 2017 - Accepted: 20 December 2017 Abstract In current research, the Friction Stir Welding (FSW) technique was used to create a metallurgical joint between Al 6061 plates and Cu meat core. The plates were welded using single pass weld with the rotational speed of 1000 rpm and arc travel speed of 30 mm/ min using different tool pin profiles of cylinder, triangle, and hexagonal. After the rolling process and reaching to 1.7 mm of thickness, to evaluate whether there was no separation in layer plates, the radiography test was applied. For more investigation of the created metallurgical bond, optical microscopy (OM) and scanning electron microscopy (SEM) were used. Studies on the welded samples showed a perfect metallurgical bonding. The bonding thickness between Al plates and the Cu meat sample in the samples with pin profiles of triangle, cylinder and hexagonal shape were estimated to be 30, 39 and 45 μm, respectively. Moreover, in comparison to the FSW samples with triangle and cylinder pin profile, the microhardness and ultimate tensile stress were higher in the FSW samples using hexagonal pin profile. It was owing to the fact that hexagonal pin profile had a larger contact area compared with the other two pins. Therefore, the mechanical work using hexagonal pin was more, resulting in an increase in the hardness and tensile stress. In addition, material flow in the bonding zone increased and contributed to an increase in the width of the joint area. Keywords: Friction Stir Welding, Al 6061, Mechanical Properties 1. Introduction Friction Stir Welding has been developed since 1991. Processed surfaces using this technique showed improved properties of hardness, tensile stress, fatigue, corrosion and also erosion and wear resistance. On the other hand, soft microstructures with coaxial recrystallized grains improved the super plasticity behavior. Moreover, this process is capable of breaking the large particles and dispersing them homogenously over a lattice. This characteristic contributes to an increase in the material tolerance for deformation and increases the strength [1]. In FSW, the contact of the pin with the surface of the work piece and diffusion in its surface contribute to the generation of heat and due to the friction, the surface of the base metal undergoes plastic deformation. The rotation of the pin causes the materials to transfer from the front to the back of the pin. This severe plastic deformation and the consequent increase in its temperature result in a surface structure of coaxial recrystallized micro grains. Recently, the application of FSW has been reported for producing metallurgical joints with high strength in a variety of materials [2]. The process of producing plates is being researched * Corresponding author Email address: k_amini@iautiran.ac.ir and developed all over the world using different and designs. In this regard, Monolithic plates comprised of U–Mo alloy based foils encapsulated in aluminum alloy cladding are proposed for conversion of some high performance research reactors to low enriched uranium fuel reactors. Three different fabrication techniques have been considered and evaluated at INL for the fabrication: Hot Isostatic Pressing (HIP), Friction Stir Welding (FSW), and Transient Liquid Phase Bonding (TLPB) [3]. Moore et al. [4] evaluated and compared the process of fabrication of the homogeneous metal plates versus the dispersion aluminum plates. The results of their research showed that FSW technique was applicable for fabrication of metal plates. In addition, an increase in the tensile stress of the created bonding using Friction Stir Welding was observed in comparison to Fusion Welding. During 2007, two of these aluminum plates were exposed to the radiation in Advanced Test Reactor (ATR) in which acceptable results were obtained. Indeed, Moore et al. [4] also investigated the Hot Isostatic Pressing to fabricate metal plates. They concluded that these plates were fabricated with acceptable results when they were subjected to the radiation in ATR. Besides, Lisboa et al. [5] studied on fabrication of aluminum plates with sputtering and transient liquid phase bonding (TLPB) techniques.