Exploring critical behavioral differences in physical, structural, and nuclear radiation attenuation properties of produced High Entropy Alloy (HEA) and Refractory-High Entropy Alloy (RHEA) samples

Güler Seval Hale,Güler Ömer,Kavaz E.,Almisned Ghada,Issa Bashar,Tekin H.O. 한국물리학회 2024 Current Applied Physics Vol.58 No.-

Refractory-High entropy alloys (RHEAs) are known for their exceptional mechanical and radiation-resistant properties, making them promising materials for use in nuclear reactors. Their high entropy composition, which consists of multiple elements in roughly equal proportions, can create a stable microstructure that withstands high levels of radiation damage. The objective of this work is to further our comprehension of the unique behavioral, physical, structural, and nuclear radiation attenuation characteristics shown by High-Entropy Alloys (HEA) and Refractory-High entropy alloy (RHEA) materials. Accordingly, two high entropy alloy (HEA) samples through two different compositions were produced. The first composition under consideration is the typical high-entropy alloy (HEA) defined as MnCrFeNiCoMo0.5. The second composition under consideration is a refractory high entropy alloy (RHEA) characterized by the following elemental composition: TiZrNbHfVTa0.1. SEM and EDX analyses were conducted in terms of determining their physical and structural attributes. Next, a133Ba radioisotope together with a HPGe detector were utilized for gamma-ray transmission experiments. Finally, a241Am/Be source and a gas proportional detector were used for neutron absorption experiments for HEA and RHEA samples. The alloy structures displayed a unique degree of uniformity. Throughout the RHEA phase, the incorporation of refractory elements did not provide any discernible adverse impacts on the physical stability. The counting spectrum provided a clear explanation of the gamma ray absorption features shown by the RHEA (R) sample, highlighting its exceptional absorption properties. Regarding the absorption properties of neutrons, it was observed that RHEA had a comparatively reduced amount of absorption. Therefore, it can be concluded that the basic structure of RHEA grants it superior gamma-ray attenuation qualities compared to HEA. It can be concluded that RHEA demonstrates superior applicability as a material in comparison to HEA, especially in situations involving the use of fuel rods, where maintaining of neutron quantity has paramount importance for achieving optimum neutron activation.

기계적 합금화를 이용한 Al0.75V2.82CrZr 내화 고엔트로피 합금의 경량화 및 고온 열안정성 연구

김민수,이한성,안병민 한국분말재료학회 2023 한국분말재료학회지 (KPMI) Vol.30 No.6

High-entropy alloys (HEAs) are characterized by having five or more main elements and forming simple solids without forming intermetallic compounds, owing to the high entropy effect. HEAs with these characteristics are being researched as structural materials for extreme environments. Conventional refractory alloys have excellent hightemperature strength and stability; however, problems occur when they are used extensively in a high-temperature environment, leading to reduced fatigue properties due to oxidation or a limited service life. In contrast, refractory entropy alloys, which provide refractory properties to entropy alloys, can address these issues and improve the hightemperature stability of the alloy through phase control when designed based on existing refractory alloy elements. Refractory high-entropy alloys require sufficient milling time while in the process of mechanical alloying because of the brittleness of the added elements. Consequently, the high-energy milling process must be optimized because of the possibility of contamination of the alloyed powder during prolonged milling. In this study, we investigated the hightemperature oxidation behavior of refractory high-entropy alloys while optimizing the milling time.

밀링 조건이 고엔트로피 합금의 미세조직 및 기계적 특성에 미치는 영향

서남혁,전준협,김광훈,박정빈,손승배,이석재,Seo, Namhyuk,Jeon, Junhyub,Kim, Gwanghoon,Park, Jungbin,Son, Seung Bae,Lee, Seok-Jae 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.2

High-entropy alloys have excellent mechanical properties under extreme environments, rendering them promising candidates for next-generation structural materials. It is desirable to develop non-equiatomic high-entropy alloys that do not require many expensive or heavy elements, contrary to the requirements of typical high-entropy alloys. In this study, a non-equiatomic high-entropy alloy powder Fe_49.5Mn₃₀Co₁₀Cr₁₀C_0.5 (at.%) is prepared by high energy ball milling and fabricated by spark plasma sintering. By combining different ball milling times and ball-to-powder ratios, we attempt to find a proper mechanical alloying condition to achieve improved mechanical properties. The milled powder and sintered specimens are examined using X-ray diffraction to investigate the progress of mechanical alloying and microstructural changes. A miniature tensile specimen after sintering is used to investigate the mechanical properties. Furthermore, quantitative analysis of the microstructure is performed using electron backscatter diffraction.

Chemical evolution-induced strengthening on AlCoCrNi dual-phase high-entropy alloy with high specific strength

Jumaev, Elyorjon,Hong, Sung Hwan,Kim, Jeong Tae,Park, Hae Jin,Kim, Young Seok,Mun, Sang Chul,Park, Jun-Young,Song, Gian,Lee, Jong Kook,Min, Byung Ho,Lee, Taegyu,Kim, Ki Buem Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.777 No.-

<P><B>Abstract</B></P> <P>Quaternary AlCoCrNi alloy was designed by removing the heavy constituent of Fe from the dual-phase AlCoCrFeNi high-entropy alloy to achieve low density with good mechanical properties. The AlCoCrNi alloy exhibited a nano-scale dual-phase structure consisted of Cr-rich A2 and Ni(Co)-Al-rich B2 phases with a high degree of coherence in both dendritic and interdendritic regions. In particular, the Ni(Co)-Al-rich B2 phase revealed the non-stoichiometric composition between the Ni and the Al, which deviated with the Ni-Al-rich B2 phase with a stoichiometric composition in the previous AlCoCrFeNi high-entropy alloy. The chemical evolution in the constituent phases strongly affected the mechanical properties of the dual-phase high-entropy alloy. Based on these microstructural features of the AlCoCrNi alloy, the mechanical properties were systematically investigated at wide temperature ranges.</P> <P><B>Highlights</B></P> <P> <UL> <LI> AlCoCrNi alloy is designed by modulating from the AlCoCrFeNi HEA. </LI> <LI> Nano-scaled Cr-rich A2 and Ni(Co)Al-rich B2 phases are formed in ID and DR regions. </LI> <LI> The Ni(Co)Al-rich B2 phase exhibits non-stoichiometric composition between Ni and Al. </LI> <LI> The chemical evolution on B2 phase induces a strengthening of the AlCoCrNi alloy. </LI> <LI> The alloy with a low density of 6.9 gcm<SUP>−3</SUP> reveals superior specific strength at wide temperature ranges. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

High Temperature Oxidation Resistance of NiCoCrAl High Entropy Alloy Coating on the TiAl Alloy

Yuanyuan Sun,Qiang Miao,Wenping Liang,Kai Zang,Yuting Wu,Haiyang Yu,Mengjuan Yin,Xiguang Gao,Yindong Song 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.1

The high entropy alloy coating is considered as one of the most promising methods to improve the high-temperature oxidationresistance of titanium aluminum alloys due to its fine mechanical property and thermal stability. However, the high entropyalloy coating prepared so far has poor coating quality, and low coating forming efficiency and there are certain requirementsfor the substrate alloys. To this end, a NiCoCrAl high entropy alloy coating was developed using the double glow plasmaalloying technique on the TiAl alloy. The morphology, phase structure, and high temperature oxidation resistance of thecoating were comprehensively studied. The results indicate that a uniform and dense coating with a single solid solution offace-centered cube phase formed on the alloy surface. Furthermore, isothermal oxidation test was performed, and the oxidationfailure process of the TiAl substrate and the NiCoCrAl-coated sample with different oxidation times was analyzed. It isfound that the coating efficiently prevented the TiAl alloy from degeneration for up to 100 h at 900 °C.

Mechanical behavior and solid solution strengthening model for face-centered cubic single crystalline and polycrystalline high-entropy alloys

Moon, Jongun,Jang, Min Ji,Bae, Jae Wung,Yim, Dami,Park, Jeong Min,Lee, Jehyun,Kim, Hyoung Seop Elsevier 2018 INTERMETALLICS Vol.98 No.-

<P><B>Abstract</B></P> <P>In the present work, a solid solution strengthening effect in high-entropy alloys (HEAs) was studied by investigating mechanical characteristics of single crystalline CoCrFeMnNi HEA and a corresponding model was developed. (100) and (110) oriented single crystals of the CoCrFeMnNi alloy were grown and their single crystallinity was identified using X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD) analyses. The mechanical testing of the single crystalline CoCrFeMnNi alloy was performed and the critical resolved shear stress (CRSS) was obtained. A solid solution strengthening modeling based on the lattice friction stress and an intrinsic residual strain of HEAs was performed. The solid solution strengthening effect of HEAs was verified using the model proposed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mechanical behavior of CoCrFeMnNi single crystals shows a typical face-centered cubic single crystal response. </LI> <LI> The root mean square residual strain of a CoCrFeMnNi alloy system was calculated using a geometrical model. </LI> <LI> A novel model for solid solution strengthening in high-entropy alloys was developed. </LI> <LI> The proposed model predicts the intrinsic yield strength of face-centered cubic high-entropy alloys with remarkable accuracy. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Strengthening Mechanisms and Deformation Behavior of Industrially-Cast and Lab-Cast Dual-Phase High Entropy Alloy

Samrat Tamuly,Saurabh Dixit,Boopathy Kombaiah,Prasenjit Khanikar 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.1

An iron-rich high entropy alloy Al0.65CoCrFe2Nicomprising of both FCC and BCC phases was designed and fabricated usinginduction melting at a large industrial scale and suction casting at a small lab scale. Spinodally decomposed interdendriticregions were uniformly distributed in the industrially melted alloy, and a finer dendritic structure with smaller sized spinodalstructures was observed in the alloy suction cast at lab scale. The suction cast alloy fabricated at the lab scale exhibitedsignificantly higher compressive yield strength compared to the industrially cast alloy. The relative strengthening contributionsin the alloys due to solid solution, grain boundary, dislocation interactions and interphase boundary were analyzed. Dislocation hardening was the major contributor responsible for the higher strength of the SC alloy. The deformation behaviorin the alloys was examined with the help of orientation image mapping. Intense slip band formation at large strains in theindustrially melted alloy indicates that cold working can be an effective technique to enhance the strength of the dual-phasehigh entropy alloy processed at a large scale.

Transition in microstructural and mechanical behavior by reduction of sigma-forming element content in a novel high entropy alloy

Raza, Ahmad,Kang, Byungchul,Lee, Junho,Ryu, Ho Jin,Hong, Soon Hyung Elsevier 2018 Materials & Design Vol.145 No.-

<P><B>Abstract</B></P> <P>A novel CrFeMoVMn<SUB>x</SUB> high entropy alloy (HEA) system was devised after screening done with thermodynamic constraints. The Mn content was varied (x=0, 0.5, 1 atomic ratio), with other elements kept in equiatomic ratios, to determine the effect of paired sigma-forming element (PSFE) content on microstructural and mechanical behavior. Alloys were successfully fabricated using a powder metallurgical method after mechanical alloying (MA) for an optimized minimum milling time. The milled powder was sintered using spark plasma sintering (SPS). The microstructural analysis indicated the appearance of a σ phase in the equiatomic quinary CrFeMoVMn<SUB>x</SUB> system, and the volume fraction of the σ phase varied directly by Mn content. The Mn0 system exhibited the formation of a single phase solid solution. The failure of thermodynamic prediction, the role of PSFE content and Md ¯ in σ phase appearance were investigated. The transition in mechanical behavior through a reduction in Mn content was also investigated and Mn1 exhibited the highest fracture strength, of 3183MPa, and hardness of 868 Hv, while Mn0 displayed the highest plasticity. This study demonstrates higher specific yield strength and hardness values compared to previously reported HEA systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The mechanical alloying optimization process have been illustrated schematically specifically for high-entropy alloys. </LI> <LI> The proposed alloy systems have challenged the thermodynamic predictions and formed sigma phase. </LI> <LI> The volume fraction of sigma phase is related with the concentration of paired sigma forming elements (PSFE) content. </LI> <LI> The alloys showed higher specific yield strength and hardness as compare to previously reported high-entropy alloy systems. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Microstructures and mechanical properties of mechanically alloyed and spark plasma sintered Al_0.3CoCrFeMnNi high entropy alloy

Pohan, Rizaldy M.,Gwalani, Bharat,Lee, Junho,Alam, Talukder,Hwang, J.Y.,Ryu, Ho Jin,Banerjee, Rajarshi,Hong, Soon Hyung Elsevier 2018 Materials chemistry and physics Vol.210 No.-

<P><B>Abstract</B></P> <P>The present study focuses on phase evolution in Al<SUB>0.3</SUB>CoCrFeMnNi high entropy alloys (HEAs) during mechanical alloying and after spark plasma sintering. Aluminium addition hardens and induces ordered precipitates in a soft <I>fcc</I> alloy based on CoCrFeMnNi. Mechanical alloying of the alloy powders resulted in a single <I>fcc</I> phase. However, ordered B2 precipitates and chromium carbide precipitates were observed after spark plasma sintering. Sintering temperature optimization was done and maximum densification and hardness were obtained at 900 °C. High compressive yield strength of 979 ± 20 MPa and compressive ductility of 39 ± 3% were observed for the SPS processed alloy. Significant contributions from grain boundary strengthening coupled with dispersion strengthening via carbides and B2 particles appear to be major contributors to alloy strengthening. These hard intermetallic particles not only keep the grain growth in check but also increase the cumulative (fcc + B2) strength of the material.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Al<SUB>0.3</SUB>CoCrFeMnNi high entropy alloy was prepared using Spark Plasma Sintering. </LI> <LI> Optimum density and grain size is obtained at 900 °C sintering temperature. </LI> <LI> Microstructure consisted of fcc matric, ordered bcc (B2) and chromium carbides. </LI> <LI> Alloy showed high compressive strength of 979 MPa and failure strain of 39%. </LI> </UL> </P>

Strengthening of Al_0.15CoCrCuFeNiTi_<i>x</i>–C (<i>x</i> = 0, 1, 2) high-entropy alloys by grain refinement and using nanoscale carbides via powder metallurgical route

Nam, Seungjin,Kim, Moon J.,Hwang, Jun Yeon,Choi, Hyunjoo Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.762 No.-

<P><B>Abstract</B></P> <P>In this study, Al<SUB>0.15</SUB>CoCrCuFeNiTi<SUB> <I>x</I> </SUB>–C (<I>x</I> = 0, 1, 2) high-entropy alloys (HEAs) were produced via powder metallurgy routes, and the microstructural evolution and mechanical properties of the alloys were investigated with respect to the alloys of Ti content. Cr-carbides were formed in the Ti-free alloy, whereas the Ti-containing alloys contained Ti-carbides instead of Cr-carbides because Ti has a higher affinity for C than it does for Cr. Sigma phases were also formed in the Al<SUB>0.15</SUB>CoCrCuFeNiTi<SUB>2</SUB>-C alloy. The formation of carbides and intermetallic compounds altered the composition and structure of the solid-solution phases. High-energy ball-milling led to the refinement of microstructures to the nanoscale, and the average grain size of the alloys decreased with increasing Ti content because of the grain-boundary pinning effect of TiC. As a result, the Al<SUB>0.15</SUB>CoCrCuFeNiTi<SUB> <I>x</I> </SUB>–C (<I>x</I> = 0, 1, 2) alloys exhibited high strengths of 2047, 2199, and 2877 MPa, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Al<SUB>0.15</SUB>CoCrCuFeNiTi<SUB>x</SUB>-C HEAs were fabricated via powder metallurgy. </LI> <LI> Microstructural evolution and mechanical properties of the alloys were investigated. </LI> <LI> Different carbides were formed in the alloy depending on Ti content. </LI> <LI> Al<SUB>0.15</SUB>CoCrCuFeNiTi<SUB>2</SUB>-C alloy revealed solid-solution phases, carbide, and intermetallic compound. </LI> <LI> Al<SUB>0.15</SUB>CoCrCuFeNiTi<SUB>2</SUB>-C alloy shown the outstanding specific yield strength of 0.429 MPa/kg·m<SUP>3</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>