Abstract
Multi-element systems with defined entropy (HEA—high entropy alloy or MEA—medium entropy alloy) are rather new material concepts that are becoming increasingly important in materials research and development. Some HEA systems show significantly improved properties or combinations of properties, e.g., the overcoming of the trade-off between high strength and ductility. Thus, the synthesis, the resulting microstructures, and properties of HEA have been primarily investigated so far. In addition, processing is crucial to achieve a transfer of potential HEA/MEA materials to real applications, e.g., highly stressed components. Since fusion welding is the most important joining process for metals, it is of vital importance to investigate the weldability of these materials. However, this has rarely been the subject of research to date. For that reason, in this work, the weldability depending on the surface preparation of a CoCrFeMnNi HEA and a CoCrNi MEA for TIG welding is investigated. The fusion welding of longer plates is described here for the first time for the CoCrNi alloy. The welds of both materials showed distinct formation of cracks in the heat affected zone (HAZ). Optical and scanning electron microscopy analysis clearly confirmed an intergranular fracture topography. However, based on the results, the crack mechanism cannot be conclusively identified as either a liquid metal embrittlement (LME) or hot cracking-like liquid film separation.
Highlights
High and medium entropy alloys (HEAs and MEAs) have steadily gained interest in worldwide research since their introduction [1,2,3]
The images of the welds with ground surface do not show any obvious weld imperfections after radiographic inspection (Figure 4b,c). These results from identical welding tests with different surface preparations clearly show that electrical discharge machining (EDM) surfaces lead to cracks in the heat affected zone (HAZ), which can be avoided by additional grinding
The initial condition for the weldability had been influenced by two different machining conditions in terms of EDM as-machined and further grinding of the samples’
Summary
High and medium entropy alloys (HEAs and MEAs) have steadily gained interest in worldwide research since their introduction [1,2,3]. HEAs and MEAs are defined as compositionally complex and disordered single-phase solid solutions containing two to four elements for MEAs and at least five elements for HEAs in nearly equiatomic proportions [4]. Due to their outstanding properties (e.g., high ductility combined with high strength), both HEAs and MEAs have the potential to replace conventional alloys such as Fe-based steels and are promising for a wide range of applications [3,4,5]. Applications exposed to cryogenic conditions could be fields of application for these materials, such as liquified cryo gas storage tanks and pipes in the energy and chemical industries
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