Interfacial Phases Formed In Friction Stir Lap Welding High Entropy Alloy To Al Alloy

The formation of intermetallic compounds (IMCs) at the joint interface between dissimilar metals has been the focus of recent research, since joint properties are largely determined by these interfacial IMCs. In this study, FeCoCrNiMn high entropy alloy (HEA) was joined to traditional 1060Al alloy by friction stir lap welding (FSLW) for the purpose of reducing the excessive cost of HEAs. Microstructural characterization shows the interfacial layer is continuous but varies in thickness from 1.3 to 1.7 mu m. The interfacial structure can be divided into three types. Close to the Al side are STR I and II, confirmed to be of same monoclinic Al13Fe4 type IMC, but showing sharp difference in composition with simultaneous co-depletion of Cr and Mn and co-enrichment of Co and Ni in STR I. Close to the HEA side is STR III, consisting of parallelly arranged ultra-fine columnar grains, identified to be orthorhombic Al5Fe2 type IMC. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.