Effect of post weld heat treatment on the microstructure and mechanical properties of gas tungsten arc welded Al0.3CoCrFeNi high entropy alloy

The authors gratefully acknowledge ECR-SERB (grant number ECR/2017/001278 ) for funding the project and FE-SEM & TEM facility at Department of MSME, IIT Hyderabad . We thank Chenna Krishna for providing the starting material and we also thank Radha Ambe for discussions in the manuscript. JPO acknowledges funding by national funds from FCT - Fundação para a Ciência e a Tecnologia, I.P. , in the scope of the projects LA/P/0037/2020 , UIDP/50025/2020 and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication – i3N. Publisher Copyright: © 2023 The Author(s)In this work, a single-phase Al0.3CoCrFeNi high entropy alloy is successfully joined by gas tungsten arc welding (GTAW). Microstructural analysis revealed the presence of equiaxed grains and annealing twins in the base material, while the same FCC structure with coarse grains and columnar dendrites are identified in the heat-affected zone and fusion zones, respectively. Further, post-weld heat treatment (PWHT) of the welded joint at 1100 °C for 1hr facilitates the formation of B2/BCC precipitates in the FCC matrix. The as-received material showed an ultimate tensile strength of 570 MPa and elongation of 83 %. The joint efficiency is 82 %, which is attributed to the large grain size that developed in the fusion zone. The PWHT material had an improved joint efficiency of 92 %, attributed to BCC/B2 precipitates forming within the FCC matrix. This research highlights the role of PWHT in obtaining high-performing HEA joints.publishersversionpublishe

High temperature deformation behavior of Al0.2CoCrFeNiMo0.5 high entropy alloy: Dynamic strain ageing

High temperature deformation behavior of Al0.2CoCrFeNiMo0.5 high entropy alloy was investigated in fully annealed condition. Microstructural studies were performed using SEM and EBSD, prior to testing, clearly shows a fully annealed microstructure consists of secondary sigma phase in the FCC matrix. Uniaxial tensile tests were performed in the temperature range of 25–900 °C at an initial strain rate of 10−3 s−1. Serrated plastic flow behavior was observed in the intermediate temperature range of 400–600 °C. The influence of the strain rate on the critical strain corresponding to the onset of serrations were studied which indicated that the serration behavior was type A and type C. Strain rate sensitivity close to zero, decrease in the elongation and microstructural investigations suggesting that dynamic strain aging (DSA) is the responsible mechanism for the serrated flow and that the Al solute interactions with dislocations might be the possible reason for DSA. Additionally, the fractography analysis clearly indicates that there is transition in the failure mode from the transgranular fracture to the intergranular fracture. © 2022 Elsevier B.V