“…Thus, in the case of AlCrFeCoNi the aspect of the dendrites is quite round, while in the AlCrFeCoNi 1.4 sample we can observe needle forms that are oriented in different directions. The AlCrFeCoNi 1.8 sample combines rounded phases with needle-like phases, consistent with the observation reported by Cao et al 28 .…”
Section: Resultssupporting
confidence: 91%
“…Thus, in the case of AlCrFeCoNi the aspect of the dendrites is quite round, while in the AlCrFeCoNi 1.4 sample we can observe needle forms that are oriented in different directions. The AlCrFeCoNi 1.8 sample combines rounded phases with needle-like phases, consistent with the observation reported by Cao et al 28 . Figure 1 Microstructure evolution of HEAs (Ni 1 , Ni 1.4 and Ni 1.8 ) during thermal and chemical processing: ( a ), ( b ), ( c ) optical microstructure; ( d ), ( e ), ( f ) SEM as-cast microstructure; ( g ), ( h ), ( i ) SEM heat treated microstructure; ( j ), ( k ), ( l ) Thermal treated and corroded microstructure.…”
In this study the effect of three different nickel concentration on the microstructure, hardness and corrosion properties of high entropy alloys (HEAs) from AlCrFeCoNi system as an alternative material for medical instruments fabrication was investigated. The analyzed HEAs were AlCrFeCoNix obtained by vacuum arc remelting from high purity raw materials and having nickel atomic ratio x = 1.0, 1.4 and 1.8. The microscopy examination revealed the dendritic morphology for the reference alloy (AlCrFeCoNi) and that the extent of the interdendritic areas increased with the concentration of nickel while Cr was more segregated in the interdendritic areas than in dendrites. Hardness values decreased as the percentage of nickel increased due to the dissolution of the precipitates in a nickel-rich matrix and consequently the formation of continuous solid solutions. The corrosion properties of the synthesized HEAs were evaluated using a potentiodynamic polarization method. The alloys were immersed in Simulated Body Fluid during one week and the corrosion parameters were recorded. The low corrosion rates, low corrosion currents and high polarization resistance attest the good stability of these HEAs in simulated biological environment indicating their possible use for surgical and dental instruments.
“…Thus, in the case of AlCrFeCoNi the aspect of the dendrites is quite round, while in the AlCrFeCoNi 1.4 sample we can observe needle forms that are oriented in different directions. The AlCrFeCoNi 1.8 sample combines rounded phases with needle-like phases, consistent with the observation reported by Cao et al 28 .…”
Section: Resultssupporting
confidence: 91%
“…Thus, in the case of AlCrFeCoNi the aspect of the dendrites is quite round, while in the AlCrFeCoNi 1.4 sample we can observe needle forms that are oriented in different directions. The AlCrFeCoNi 1.8 sample combines rounded phases with needle-like phases, consistent with the observation reported by Cao et al 28 . Figure 1 Microstructure evolution of HEAs (Ni 1 , Ni 1.4 and Ni 1.8 ) during thermal and chemical processing: ( a ), ( b ), ( c ) optical microstructure; ( d ), ( e ), ( f ) SEM as-cast microstructure; ( g ), ( h ), ( i ) SEM heat treated microstructure; ( j ), ( k ), ( l ) Thermal treated and corroded microstructure.…”
In this study the effect of three different nickel concentration on the microstructure, hardness and corrosion properties of high entropy alloys (HEAs) from AlCrFeCoNi system as an alternative material for medical instruments fabrication was investigated. The analyzed HEAs were AlCrFeCoNix obtained by vacuum arc remelting from high purity raw materials and having nickel atomic ratio x = 1.0, 1.4 and 1.8. The microscopy examination revealed the dendritic morphology for the reference alloy (AlCrFeCoNi) and that the extent of the interdendritic areas increased with the concentration of nickel while Cr was more segregated in the interdendritic areas than in dendrites. Hardness values decreased as the percentage of nickel increased due to the dissolution of the precipitates in a nickel-rich matrix and consequently the formation of continuous solid solutions. The corrosion properties of the synthesized HEAs were evaluated using a potentiodynamic polarization method. The alloys were immersed in Simulated Body Fluid during one week and the corrosion parameters were recorded. The low corrosion rates, low corrosion currents and high polarization resistance attest the good stability of these HEAs in simulated biological environment indicating their possible use for surgical and dental instruments.
“…HEAs built of an FCC phase demonstrate remarkable ductility, 39) and those consisting of a BCC structure are very hard and have good compressive yield strength. 1,7,8,10,11) A high entropy alloy containing both phases will exhibit a compromise between the two properties; its hardness and ductility will be dependent on the respective amounts of the FCC and BCC structures constituting the material. 68,11) HEAs with both phases are desirable, because BCC-based high entropy alloys are often brittle, 7,8) whereas FCC-structured HEAs exhibit inferior hardness and yield strength.…”
Section: Introductionmentioning
confidence: 99%
“…1,7,8,10,11) A high entropy alloy containing both phases will exhibit a compromise between the two properties; its hardness and ductility will be dependent on the respective amounts of the FCC and BCC structures constituting the material. 68,11) HEAs with both phases are desirable, because BCC-based high entropy alloys are often brittle, 7,8) whereas FCC-structured HEAs exhibit inferior hardness and yield strength. 3,4,68) The above-mentioned combination of hardness, compressive strength and ductility has led to interest in these alloys as potential alternatives to commonly used alloys, e.g.…”
Section: Introductionmentioning
confidence: 99%
“…19,22) The above-mentioned lack of phase stability and necessity for lowering Al content in Al x CoCrFeNi high entropy systems has led to research on alternative methods of improving these alloys. Studies have shown that the volume fraction of the FCC phase in AlCoCrFeNi systems increases along with Ni content 11) and Co concentration. 24,25) Furthermore, so-called high entropy superalloys with Ni concentration exceeding the limit provided in the traditional HEA definition, i.e.…”
This study aims to compare the behaviour of two Ni-rich non-equimolar AlCoCrFeNi high entropy alloys, i.e. Al 20 Co 5 Cr 20 Fe 20 Ni 35 and Al 10 Co 15 Cr 20 Fe 20 Ni 35 (at%) in isothermal high-temperature oxidizing conditions. In both cases, mass gain after 100-hr oxidation at 1173 K in synthetic air atmosphere does not exceed 1 mg/cm 2 , indicating good resistance against the corrosive environment. Investigations on the morphology, chemical and phase composition of the alloys after the oxidation process indicate that a mixture of Al 2 O 3 and Cr 2 O 3 is responsible for the protective properties of the scale formed on Al 20 Co 5 Cr 20 Fe 20 Ni 35 , whereas an additional chromiumironnickelcobalt spinel structure was determined on the Al 10 Co 15 Cr 20 Fe 20 Ni 35 sample after prolonged exposure to the above-mentioned conditions. The oxidation kinetics are slightly better in the case of Al 20 Co 5 Cr 20 Fe 20 Ni 35 and lower amounts of the remaining constituent elements were detected in the protective scale compared to Al 10 Co 15 Cr 20 Fe 20 Ni 35 . Furthermore, the Al 20 Co 5 Cr 20 Fe 20 Ni 35 substrate was able to maintain its initial morphology throughout the entire alloy after the corrosion process. From all of the above, it can be concluded that Al 20 Co 5 Cr 20 Fe 20 Ni 35 seems to demonstrate better oxidation properties at a high temperature than Al 10 Co 15 Cr 20 Fe 20 Ni 35 .
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