scholarly journals Influence of Surface Preparation on Cracking Phenomena in TIG-Welded High and Medium Entropy Alloys

2021 ◽  
Vol 6 (1) ◽  
pp. 5
Author(s):  
Tim Richter ◽  
Marcel Giese ◽  
Michael Rhode ◽  
Dirk Schroepfer ◽  
Thomas Michael ◽  
...  
Keyword(s):  
Surface Preparation ◽  
High Strength ◽  
Fusion Welding ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Fracture Topography ◽  
Electron Microscopy Analysis ◽  
Materials Research ◽  
New Material ◽  
Film Separation

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.

WReTaMo Refractory High‐Entropy Alloy with High Strength at 1600 °C

2021 ◽  
pp. 2100765
Author(s):  
Yixing Wan ◽  
Qianqian Wang ◽  
Jinyong Mo ◽  
Zhibin Zhang ◽  
Xin Wang ◽  
...  
Keyword(s):  
High Strength ◽  
High Entropy Alloy ◽  
High Entropy

scholarly journals On the high temperature coarsening kinetics of γ′ precipitates in a high strength Co37.6Ni35.4Al9.9Mo4.9Cr5.9Ta2.8Ti3.5 fcc-based high entropy alloy

2019 ◽  
Vol 177 ◽  
pp. 82-95 ◽  
Author(s):  
Prafull Pandey ◽  
Sanjay Kashyap ◽  
Dhanalakshmi Palanisamy ◽  
Amit Sharma ◽  
Kamanio Chattopadhyay
Keyword(s):  
High Temperature ◽  
High Strength ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Coarsening Kinetics ◽  
Kinetics Of

scholarly journals High-Strength Behavior of the Al0.3CoCrFeNi High-Entropy Alloy Single Crystals

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1149
Author(s):  
Irina V. Kireeva ◽  
Yuriy I. Chumlyakov ◽  
Zinaida V. Pobedennaya ◽  
Anna V. Vyrodova ◽  
Anastasia A. Saraeva
Keyword(s):  
Single Crystals ◽  
Yield Point ◽  
Stress Level ◽  
High Stress ◽  
High Strength ◽  
Orientation Dependence ◽  
Temperature Deformation ◽  
High Entropy Alloy ◽  
Shear Stresses ◽  
High Entropy

The main disadvantage of fcc (face-centred cubic lattice) high-entropy alloys is the low stress level at the yield point (σ0.1) at a test temperature above room temperature. This restricts their practical application at high test temperatures from 773 K to 973 K. In this study, we found that a high stress level was reached at the yield point σ0.1 ≈ G/100–G/160 (G is the shear modulus) of the [001]- and [1¯44]-oriented crystals of the Co23.36Cr23.29Fe23.80Ni21.88Al7.67 (Al0.3CoCrFeNi) high-entropy alloy (HEA) within a wide temperature range of 77–973 K under tension, due to the occurrence, of nanotwins, multipoles, dislocations under plastic deformation at 77 K and the subsequent precipitation of ordered L12 and B2 particles. It was shown that grain boundaries are not formed and the samples remain in a single-crystal state after low-temperature deformation and subsequent ageing at 893 K for 50 h. Achieving a high-strength state in the Al0.3CoCrFeNi HEA single crystals induces the orientation dependence of the critical resolved shear stresses (τcr) at T ≥ 200 K (τcr[1¯44] > τcr[001]), which is absent in the initial single-phase crystals, weakens the temperature dependence of σ0.1 above 573 K, and reduces plasticity to 5–13% in the [1¯44] orientation and 15–20% in the [001] orientation.

scholarly journals Cutting Edge of High-Entropy Alloy Superconductors from the Perspective of Materials Research

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1078
Author(s):  
Jiro Kitagawa ◽  
Shusuke Hamamoto ◽  
Naoki Ishizu
Keyword(s):  
Material Design ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
Simple Material ◽  
Σ Phase ◽  
High Entropy ◽  
Cscl Type ◽  
Materials Research ◽  
Face Centered ◽  
New Phenomena

High-entropy alloys (HEAs) are a new class of materials which are being energetically studied around the world. HEAs are characterized by a multicomponent alloy in which five or more elements randomly occupy a crystallographic site. The conventional HEA concept has developed into simple crystal structures such as face-centered-cubic (fcc), body-centered-cubic (bcc) and hexagonal-closed packing (hcp) structures. The highly atomic-disordered state produces many superior mechanical or thermal properties. Superconductivity has been one of the topics of focus in the field of HEAs since the discovery of the bcc HEA superconductor in 2014. A characteristic of superconductivity is robustness against atomic disorder or extremely high pressure. The materials research on HEA superconductors has just begun, and there are open possibilities for unexpectedly finding new phenomena. The present review updates the research status of HEA superconductors. We survey bcc and hcp HEA superconductors and discuss the simple material design. The concept of HEA is extended to materials possessing multiple crystallographic sites; thus, we also introduce multisite HEA superconductors with the CsCl-type, α-Mn-type, A15, NaCl-type, σ-phase and layered structures and discuss the materials research on multisite HEA superconductors. Finally, we present the new perspectives of eutectic HEA superconductors and gum metal HEA superconductors.

High-strength ultrafine-grained CoCrFeNiNb high-entropy alloy prepared by mechanical alloying: Properties and strengthening mechanism

2020 ◽  
Vol 835 ◽  
pp. 155308 ◽  
Author(s):  
Filip Průša ◽  
Marcello Cabibbo ◽  
Alexandra Šenková ◽  
Vojtěch Kučera ◽  
Zbyněk Veselka ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
High Strength ◽  
Strengthening Mechanism ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Ultrafine Grained

scholarly journals Extremely high strength and work hardening ability in a metastable high entropy alloy

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
S. S. Nene ◽  
M. Frank ◽  
K. Liu ◽  
R. S. Mishra ◽  
B. A. McWilliams ◽  
...  
Keyword(s):  
Work Hardening ◽  
High Strength ◽  
High Entropy Alloy ◽  
High Entropy

scholarly journals Dynamic Shear Deformation of a Precipitation Hardened Al0.7CoCrFeNi Eutectic High-Entropy Alloy Using Hat-Shaped Specimen Geometry

2020 ◽  
Author(s):  
Bharat Gwalani ◽  
Tianhao Wang ◽  
Abhinav Jagetia ◽  
Sindhura Gangireddy ◽  
Saideep Muskeri ◽  
...  
Keyword(s):  
Shear Deformation ◽  
High Strength ◽  
Shear Loading ◽  
Adiabatic Shear ◽  
Dynamic Strain ◽  
High Entropy Alloy ◽  
Dynamic Shear ◽  
High Entropy ◽  
Structural Applications ◽  
Static Conditions

Lamellar eutectic structure of Al0.7CoCrFeNi high-entropy alloy (HEA) is emerging as a promising candidate for structural applications because of its high strength-ductility combination. The alloy consists of a fine-scale lamellar fcc+B2 microstructure with high flow stresses >1500 MPa under quasi-static conditions. The response to shear loading was not investigated so far. This is the first report on the shear deformation of an eutectic structured HEA and effect of precipitation on shear deformation. The dynamic shear response (DSR) of the eutectic HEA was examined in two microstructural conditions, with and without the presence of L12 precipitates. A split-Hopkinson pressure bar (SHPB) was used to compress the hat-shaped specimens to study the local DSR of the alloy. The adiabatic shear bands (ASBs) in two different microstructural conditions were characterized after deformation at dynamic strain rates. The adiabatic shear localization occurs at low strains for the high strength material, and the eutectic microstructure does not delay cracking. The width of ASBs and the extent of plastic deformation around them has been correlated with the rate of straining. Dynamic recrystallization within ASBs and profuse twinning around it was observed. Local mechanical response of individual lamellae before and after shear deformation was examined using nano-indentation.

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