Dissimilar welding of Al 0.1 CoCrFeNi high-entropy alloy and AISI304 stainless steel
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Dissimilar welding of Al0.1CoCrFeNi high-entropy alloy and AISI304 stainless steel Rathinavelu Sokkalingam1, Veerappan Muthupandi1, Katakam Sivaprasad1,a), Konda Gokuldoss Prashanth2,b) 1
Advanced Materials Processing Laboratory, Department of Metallurgical aqnd Materials Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu 620015, India 2 Department of Mechanical and Industrial Engineering, Tallinn University of Technology, Tallinn 19086, Estonia; and Austrian Academy of Science, Erich Schmid Institute of Materials Science, A-8700 Leoben, Austria a) Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] Received: 20 February 2019; accepted: 3 May 2019
High-entropy alloys (HEAs) have been proven to exhibit superior structural properties from cryogenic to high temperatures, demonstrating their structural stability against the formation of complex intermetallic phases or compounds as major fractions. These characteristics can find applications in nuclear and aerospace sectors as structural materials. As the dissimilar joint design is necessary for such applications, an attempt is made to fabricate the dissimilar transition joint between Al0.1CoCrFeNi-HEA and AISI304 austenitic stainless steel by conventional tungsten inert gas welding. Microstructural characterization by SEM and EBSD clearly revealed the evolution of columnar dendritic structures from the interfaces and their transformation to equiaxed dendritic grains as they reach the weld center. Also, considerable grain coarsening was observed in the heat-affected zone of the HEA. The tensile test results depict that the dissimilar weld joint showed significantly higher tensile strength (590 MPa) than the HEA (327 MPa), making it suitable for structural applications.
Introduction Because of increased energy demands and climatic concerns, efforts are being made to improve the efficiency of thermal and nuclear power plants. Hence, the future innovative nuclear reactor requires structural materials with characteristics such as high temperature structural stability (975–1025 K); better dimensional stability with or without the application of load; and acceptable mechanical properties such as tensile strength, fracture toughness, and creep resistance after aging; and better resistance to severe corrosive reactor environments while handling the reactor coolants and other processing fluids [1, 2, 3]. High-entropy alloys (HEAs) are developed based on the novel concept of multi-principal elemental alloying and are currently gaining worldwide attention. HEAs are a simple substitutional solid solution with a single crystal structure or a combination of simple crystal structures, such as facecentered cubic (fcc), body-centered cubic (bcc), or hexagonal closed pack (hcp) structures, instead of the formation of complex intermetallic compounds. Formation of the simple
ª Materials Research Society 2019
solid solution is attributed to the reduction in Gibbs free energy for the solid solution due to the enhancement
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