scholarly journals Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys

AIP Advances ◽  
2018 ◽  
Vol 8 (5) ◽  
pp. 056412 ◽  
Author(s):  
Suok-Min Na ◽  
Jin-Hyeong Yoo ◽  
Paul K. Lambert ◽  
Nicholas J. Jones
Keyword(s):  
Temperature Dependence ◽  
Room Temperature ◽  
High Entropy Alloys ◽  
High Entropy

scholarly journals The Effect of Boron on the Microstructure and Properties of Refractory Metal Intermetallic Composites (RM(Nb)ICs) Based on Nb-24Ti-xSi (x = 16, 17 or 18 at.%) with Additions of Al, Cr or Mo

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6101
Author(s):  
Tophan Thandorn ◽  
Panos Tsakiropoulos
Keyword(s):  
Refractory Metal ◽  
Design Methodology ◽  
Room Temperature ◽  
High Entropy Alloys ◽  
Scale Spallation ◽  
High Entropy ◽  
Specific Strength ◽  
Arc Melting ◽  
High Temperature Materials ◽  
Heat Treated

This paper is about metallic ultra-high temperature materials, in particular, refractory metal intermetallic composites based on Nb, i.e., RM(Nb)ICs, with the addition of boron, which are compared with refractory metal high entropy alloys (RHEAs) or refractory metal complex concentrated alloys (RCCAs). We studied the effect of B addition on the density, macrosegregation, microstructure, hardness and oxidation of four RM(Nb)IC alloys, namely the alloys TT2, TT3, TT4 and TT8 with nominal compositions (at.%) Nb-24Ti-16Si-5Cr-7B, Nb-24Ti-16Si-5Al-7B, Nb-24Ti-18Si-5Al-5Cr-8B and Nb-24Ti-17Si-3.5Al-5Cr-6B-2Mo, respectively. The alloys made it possible to compare the effect of B addition on density, hardness or oxidation with that of Ge or Sn addition. The alloys were made using arc melting and their microstructures were characterised in the as cast and heat-treated conditions. The B macrosegregation was highest in TT8. The macrosegregation of Si or Ti increased with the addition of B and was lowest in TT8. The alloy TT8 had the lowest density of 6.41 g/cm3 and the highest specific strength at room temperature, which was also higher than that of RCCAs and RHEAs. The Nbss and T2 silicide were stable in the alloys TT2 and TT3, whereas in TT4 and TT8 the stable phases were the Nbss and the T2 and D88 silicides. Compared with the Ge or Sn addition in the same reference alloy, the B and Ge addition was the least and most effective at 800 °C (i.e., in the pest regime), when no other RM was present in the alloy. Like Ge or Sn, the B addition in TT2, TT3 and TT4 did not suppress scale spallation at 1200 °C. Only the alloy TT8 did not pest and its scales did not spall off at 800 and 1200 °C. The macrosegregation of Si and Ti, the chemical composition of Nbss and T2, the microhardness of Nbss and the hardness of alloys, and the oxidation of the alloys at 800 and 1200 °C were also viewed from the perspective of the alloy design methodology NICE and relationships with the alloy or phase parameters VEC, δ and Δχ. The trends of these parameters and the location of alloys and phases in parameter maps were found to be in agreement with NICE.

Mn Cr0.3Fe0.5Co0.2Ni0.5Al0.3 high entropy alloys for magnetocaloric refrigeration near room temperature

2021 ◽  
Vol 79 ◽  
pp. 15-20
Author(s):  
Zhihua Dong ◽  
Shuo Huang ◽  
Valter Ström ◽  
Guocai Chai ◽  
Lajos Károly Varga ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Entropy Alloys ◽  
High Entropy

scholarly journals Microstructure and Room Temperature Mechanical Properties of Different 3 and 4 Element Medium Entropy Alloys from HfNbTaTiZr System

Entropy ◽  
2019 ◽  
Vol 21 (2) ◽  
pp. 114 ◽  
Author(s):  
Jiří Zýka ◽  
Jaroslav Málek ◽  
Jaroslav Veselý ◽  
František Lukáč ◽  
Jakub Čížek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Testing ◽  
Room Temperature ◽  
High Entropy Alloys ◽  
Lower Strength ◽  
X Ray ◽  
High Entropy ◽  
Elongation To Failure ◽  
Zero Values ◽  
Bcc Phase

Refractory high entropy alloys (HEA) are promising materials for high temperature applications. This work presents investigations of the room temperature tensile mechanical properties of selected 3 and 4 elements medium entropy alloys (MEA) derived from the HfNbTaTiZr system. Tensile testing was combined with fractographic and microstructure analysis, using scanning electron microscope (SEM), wavelength dispersive spectroscope (WDS) and X-Ray powder diffraction (XRD). The 5 element HEA alloy HfNbTaTiZr exhibits the best combination of strength and elongation while 4 and 3 element MEAs have lower strength. Some of them are ductile, some of them brittle, depending on microstructure. Simultaneous presence of Ta and Zr in the alloy resulted in a significant reduction of ductility caused by reduction of the BCC phase content. Precipitation of Ta rich particles on grain boundaries reduces further the maximum elongation to failure down to zero values.

Effect of Al Content on Microstructure and Properties of AlxMoNbTiV RCCA’s Alloys

2018 ◽  
Vol 941 ◽  
pp. 1111-1116 ◽  
Author(s):  
Antoine Lacour-Gogny-Goubert ◽  
Zhao Zhao-Huvelin ◽  
Agnès Bachelier-Locq ◽  
Ivan Guillot ◽  
Anne Denquin
Keyword(s):  
Room Temperature ◽  
High Entropy Alloys ◽  
Compression Tests ◽  
Micro Hardness ◽  
High Entropy ◽  
Al Content ◽  
Arc Melting ◽  
Bcc Structure ◽  
The Stability ◽  
Cast Microstructure

The objective of this study is the evaluation of high entropy alloys for aeroengines applications up to 1000°C. AlxNbMoTiV alloys with 10 and 20 at.% Al have been produced by arc melting. As-cast microstructure and phase transformations during heat treatments have been investigated through SEM, DRX and TEM, revealing the possibility of homogenization at 1400°C and the stability of the BCC structure at 1000°C and 800°C for both alloys. Mechanical properties have been evaluated through micro-hardness and compression tests up to 800°C. It appears that, although both alloys show a similar microstructure and hardness evolution with heat treatment, the Alloy containing 10 at.% of Al show a higher yield strength at room temperature and 800°C, related to the brittle character of the alloy containing 20 at.% of Al.

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