Intermetallics最新文献

英文中文

High-temperature oxidation behavior of Nbx(MoTaW)(1-x) (x = 0.25, 0.4, 0.55, and 0.7) refractory multicomponent alloys

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-02-01 DOI: 10.1016/j.intermet.2024.108604

Anjali Kanchi , Koteswararao V. Rajulapati , Vijayaraghavan Ganesan , Ravi C. Gundakaram

A detailed microstructural and structural study of the high-temperature oxidation behavior of refractory multicomponent alloys (RMCAs) with composition Nb_x(MoTaW)_(1-x) (x = 0.25, 0.4, 0.55, and 0.7 at%, designated as Nb_0.25, Nb_0.4, Nb_0.55, and Nb_0.7 respectively) was carried out as a function of Nb content at temperatures of 873K, 973K, and 1073K for durations up to 9h. Before the oxidation test, the RMCAs mentioned above had the single-phase BCC structure. Thermogravimetric curves demonstrated a weight gain with increase in temperature, time, and Nb concentration, showing that Nb_0.7 has low oxidation resistance. The weight gain curves were fitted using a power law equation and it was observed that the data show a good fit for the linear oxidation behavior for all samples. Quantification of the activation energy for oxide formation revealed that a higher Nb content results in a lower activation energy, suggesting poor oxidation resistance. XRD patterns show that in the above oxidized RMCAs, simple oxides such as Nb₂O₅, Ta₂O₅, MoO₃, and WO₃ form at 873K since these have the lowest free energy of formation. At 973K and 1073K, these simple oxides react to produce complex oxides such as Nb₂W₃O₁₄, Nb₁₄W₃O₄₄, and Ta₈W₉O₄₇, with a fraction of the simple oxides continuing to be present. As the temperature and Nb concentration increased, the surface morphology of RMCAs, as studied by SEM, revealed the presence of a discontinuous non-protective oxide layer with pores, bursts, nano-sized rod-shaped particles and cracks. In this study, Nb_0.25 exhibits superior oxidation resistance as compared to other RMCAs.

{"title":"High-temperature oxidation behavior of Nbx(MoTaW)(1-x) (x = 0.25, 0.4, 0.55, and 0.7) refractory multicomponent alloys","authors":"Anjali Kanchi , Koteswararao V. Rajulapati , Vijayaraghavan Ganesan , Ravi C. Gundakaram","doi":"10.1016/j.intermet.2024.108604","DOIUrl":"10.1016/j.intermet.2024.108604","url":null,"abstract":"<div><div>A detailed microstructural and structural study of the high-temperature oxidation behavior of refractory multicomponent alloys (RMCAs) with composition Nbx(MoTaW)(1-x) (x = 0.25, 0.4, 0.55, and 0.7 at%, designated as Nb0.25, Nb0.4, Nb0.55, and Nb0.7 respectively) was carried out as a function of Nb content at temperatures of 873K, 973K, and 1073K for durations up to 9h. Before the oxidation test, the RMCAs mentioned above had the single-phase BCC structure. Thermogravimetric curves demonstrated a weight gain with increase in temperature, time, and Nb concentration, showing that Nb0.7 has low oxidation resistance. The weight gain curves were fitted using a power law equation and it was observed that the data show a good fit for the linear oxidation behavior for all samples. Quantification of the activation energy for oxide formation revealed that a higher Nb content results in a lower activation energy, suggesting poor oxidation resistance. XRD patterns show that in the above oxidized RMCAs, simple oxides such as Nb2O5, Ta2O5, MoO3, and WO3 form at 873K since these have the lowest free energy of formation. At 973K and 1073K, these simple oxides react to produce complex oxides such as Nb2W3O14, Nb14W3O44, and Ta8W9O47, with a fraction of the simple oxides continuing to be present. As the temperature and Nb concentration increased, the surface morphology of RMCAs, as studied by SEM, revealed the presence of a discontinuous non-protective oxide layer with pores, bursts, nano-sized rod-shaped particles and cracks. In this study, Nb0.25 exhibits superior oxidation resistance as compared to other RMCAs.</div></div>","PeriodicalId":331,"journal":{"name":"Intermetallics","volume":"177 ","pages":"Article 108604"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Ultrastrong and ductile Fe60Co20Ni15Mo5 medium-entropy alloy with high density nanoprecipitates

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-02-01 DOI: 10.1016/j.intermet.2024.108606

Zhimin Yang , Shilin Feng , Chongxun Fang , Yongfu Cai , Zhenhua Han , Haimei Li , Ran Wei

We report a novel precipitation-strengthened Fe₆₀Co₂₀Ni₁₅Mo₅ medium entropy alloy (MEA). The MEA with single-phase BCC microstructure exhibits a high cryogenic tensile strength of ∼2.7 GPa, surpassing the state-of-the-art MEAs and high strength alloys. Besides, a unique dual-phase structure can be obtained by using the reverse process, that is, high-density spherical nanoprecipitates embedded within a BCC matrix and a minor presence of nanoprecipitates within the reverted FCC phase. Due to precipitation strengthening and transformation-induced plasticity effect, the dual-phase MEA exhibits outstanding cryogenic strength (∼2.2 GPa) and ductility (∼20 %) combinations.

引用次数: 0

Superior strain gauge sensitivity and elastic anisotropy in TiZrHfTa high entropy alloy

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-02-01 DOI: 10.1016/j.intermet.2024.108575

S.A. Uporov , I.V. Evdokimov , V.A. Sidorov , N.M. Chtchelkatchev , V.A. Bykov , E.V. Sterkhov , I.A. Balyakin , R.E. Ryltsev

A great research breakthrough that occurred in materials science twenty years ago has brought new metallurgical alloy design principles and made it possible to create a unique kind of artificial materials – multi-element concentrated alloys. These complex solid solutions reveal unique crystalline structures and promising physical and chemical properties. All of these alloys are interesting for their functionality, but they have not yet been introduced into daily life due to their high price and complexity of production. It has recently been proposed that electrical resistance strain gauges and pressure sensors are among the most suitable practical applications in which these materials can be efficiently implemented. The further development of such alloys requires an improved understanding of the physical mechanisms behind high strain gauge sensitivity in these systems. This study focuses on a comprehensive analysis of the effects of pressure and uniaxial stress on electrical resistivity in the equiatomic TiZrHfTa high-entropy alloy, which is a typical representative of this family of materials. We measure electrical, magnetic, and thermal properties of the system and calculate its electronic structure and elastic constants to address issues associated with the strain and pressure effects, as well as evaluate the overall functionality for this kind of alloys in terms of possible passive electronic sensors. The tested alloy exhibits virtually temperature-independent resistivity and a superior strain gauge factor as large as 5.17. By analyzing the obtained data, we suggest that elastic anisotropy effects play a key role in the strain-sensitive behavior of refractory high-entropy alloys.

{"title":"Superior strain gauge sensitivity and elastic anisotropy in TiZrHfTa high entropy alloy","authors":"S.A. Uporov , I.V. Evdokimov , V.A. Sidorov , N.M. Chtchelkatchev , V.A. Bykov , E.V. Sterkhov , I.A. Balyakin , R.E. Ryltsev","doi":"10.1016/j.intermet.2024.108575","DOIUrl":"10.1016/j.intermet.2024.108575","url":null,"abstract":"<div><div>A great research breakthrough that occurred in materials science twenty years ago has brought new metallurgical alloy design principles and made it possible to create a unique kind of artificial materials – multi-element concentrated alloys. These complex solid solutions reveal unique crystalline structures and promising physical and chemical properties. All of these alloys are interesting for their functionality, but they have not yet been introduced into daily life due to their high price and complexity of production. It has recently been proposed that electrical resistance strain gauges and pressure sensors are among the most suitable practical applications in which these materials can be efficiently implemented. The further development of such alloys requires an improved understanding of the physical mechanisms behind high strain gauge sensitivity in these systems. This study focuses on a comprehensive analysis of the effects of pressure and uniaxial stress on electrical resistivity in the equiatomic TiZrHfTa high-entropy alloy, which is a typical representative of this family of materials. We measure electrical, magnetic, and thermal properties of the system and calculate its electronic structure and elastic constants to address issues associated with the strain and pressure effects, as well as evaluate the overall functionality for this kind of alloys in terms of possible passive electronic sensors. The tested alloy exhibits virtually temperature-independent resistivity and a superior strain gauge factor as large as 5.17. By analyzing the obtained data, we suggest that elastic anisotropy effects play a key role in the strain-sensitive behavior of refractory high-entropy alloys.</div></div>","PeriodicalId":331,"journal":{"name":"Intermetallics","volume":"177 ","pages":"Article 108575"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The heterogeneity formation mechanism of twin wire-directed energy deposition-arc fabricated TiAl alloy

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-02-01 DOI: 10.1016/j.intermet.2024.108605

Lin Wang, Chen Shen, Yuelong Zhang, Fang Li, Wenlu Zhou, Gang Ruan, Yuhan Ding, Kanglong Wu, Xueming Hua

Additive manufacturing (AM) has become an attractive method in fabricating TiAl alloys. In addition to the well-known anisotropy, additively manufactured TiAl alloys also exhibit heterogeneity. However, research in this area has been limited. This work systematically investigates the heterogeneity formation mechanism of the twin wire-directed energy deposition-arc produced TiAl alloy. The results show that the microstructure characteristics, such as the lamellar spacing (0.39 μm–0.56 μm), colony size (186 μm–232 μm), and α₂ phase content (7 %–10 %), and microstructure degradation degree, present the tendency of increase from the upper to the lower part along the deposition direction, attributed to differences in the thermal cycle features experienced during AM. Consequently, its tensile strength (415.3 MPa–361 MPa) and elongation (0.54 %–0.38 %) also display a gradual decline from the upper to the lower part. This research contributes to a deeper understanding of the evolution of microstructure and the mechanical properties of additively manufactured TiAl alloys.

{"title":"The heterogeneity formation mechanism of twin wire-directed energy deposition-arc fabricated TiAl alloy","authors":"Lin Wang, Chen Shen, Yuelong Zhang, Fang Li, Wenlu Zhou, Gang Ruan, Yuhan Ding, Kanglong Wu, Xueming Hua","doi":"10.1016/j.intermet.2024.108605","DOIUrl":"10.1016/j.intermet.2024.108605","url":null,"abstract":"<div><div>Additive manufacturing (AM) has become an attractive method in fabricating TiAl alloys. In addition to the well-known anisotropy, additively manufactured TiAl alloys also exhibit heterogeneity. However, research in this area has been limited. This work systematically investigates the heterogeneity formation mechanism of the twin wire-directed energy deposition-arc produced TiAl alloy. The results show that the microstructure characteristics, such as the lamellar spacing (0.39 μm–0.56 μm), colony size (186 μm–232 μm), and α2 phase content (7 %–10 %), and microstructure degradation degree, present the tendency of increase from the upper to the lower part along the deposition direction, attributed to differences in the thermal cycle features experienced during AM. Consequently, its tensile strength (415.3 MPa–361 MPa) and elongation (0.54 %–0.38 %) also display a gradual decline from the upper to the lower part. This research contributes to a deeper understanding of the evolution of microstructure and the mechanical properties of additively manufactured TiAl alloys.</div></div>","PeriodicalId":331,"journal":{"name":"Intermetallics","volume":"177 ","pages":"Article 108605"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A prediction model of failure threshold for shear deformation in a Zr-based bulk metallic glass

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-02-01 DOI: 10.1016/j.intermet.2024.108602

H.R. Cheng , Z. Wang , J. Brechtl , W. Wen , M. Zhang , Z.H. Wang , J.W. Qiao

The failure of bulk metallic glasses (BMGs) during plastic deformation at room temperature is abrupt and instantaneous, while the analysis of precursor information based on avalanche events helps predict catastrophic failure. An acoustic emission (AE) signal can provide accurate precursor information for material failure, due to its sensitive and high fast calculation ability. In the current study, AE monitoring tests are carried out during uniaxial compression tests of BMGs at different strain rates. The AE experimental failure threshold, E_max, is proposed on the basis of AE cumulative energy, which reflects the intensity of damage evolution at different loading conditions. Compared with the critical shear band velocity (CSBV) associated with stick-slip dynamics of serrated flow, E_max is a more sensitive failure parameter since it is connected with the local microscopic changes that occur during the material response process. Here, the E_max is obtained prior to reaching the CSBV since the calculation of these two avalanches analysis focuses on the different stages of shear band growth. In particular, AE events are related to the “dry” friction process in the first stage, however, the CSBV is responsible for the “viscous” glide in the second stage. Therefore, E_max is not affected by the complex interactions between the shear bands during the stick-slip process. The maximum avalanche of serrated flow, S_max, is proposed as the experimental failure threshold, which depends on the applied strain rate as

S_{\max} \sim {\dot{ε}}^{- λ}

. According to the relationship of E_max and S_max, the theoretical failure threshold, E_max, follows a criterion

E_{\max} = 2545 {\dot{ε}}^{- λ} ‐ 4468

, where λ is equivalent to 0.15 for this work. Combining the different calculations and AE measurements, this model gives new insights to predict the deformation failure behavior of Zr-based BMGs.

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引用次数: 0

Revealing the disparate defect evolution paths with loading rates for ductile and brittle metallic glasses via nanoscale creep

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-02-01 DOI: 10.1016/j.intermet.2024.108584

F.C. Wang , Y.H. Gao , M.C. Jian , Y.B. Wang , Y. Huang , Y.Y. Sun , Y.Z. Liu , F. Xu , C. Kursun , Y. Zhang , J.T. Huo , J.Q. Wang , M. Gao

Ductile and brittle metallic glasses display significantly different mechanical behaviors. However, the microscopic deformation mechanisms and the defect dynamics in different metallic glasses remain unclear. In this work, an experimental strategy based on nanoscale creep was used to detect the defect evolution dynamics at different loading rates for six metallic glasses with varying plasticity. The plastic deformation ability and the strain rate sensitivity of these metallic glasses under different loading rates were systematically investigated. Furthermore, the evolution of defect volume and relaxation time spectrum under varying loading rates was analyzed utilizing the Cooperative Shearing model in conjunction with the Maxwell-Kelvin model. It was observed that ductile and brittle metallic glasses display markedly different defect dynamics at varying loading rates. Finally, a scheme was introduced to illustrate different defect evolution paths with various loading rates for ductile and brittle metallic glasses based on their heterogeneous viscoelastic structure. The study provides insights into the differences in microscopic deformation mechanism and their structural origins in various amorphous materials.

{"title":"Revealing the disparate defect evolution paths with loading rates for ductile and brittle metallic glasses via nanoscale creep","authors":"F.C. Wang , Y.H. Gao , M.C. Jian , Y.B. Wang , Y. Huang , Y.Y. Sun , Y.Z. Liu , F. Xu , C. Kursun , Y. Zhang , J.T. Huo , J.Q. Wang , M. Gao","doi":"10.1016/j.intermet.2024.108584","DOIUrl":"10.1016/j.intermet.2024.108584","url":null,"abstract":"<div><div>Ductile and brittle metallic glasses display significantly different mechanical behaviors. However, the microscopic deformation mechanisms and the defect dynamics in different metallic glasses remain unclear. In this work, an experimental strategy based on nanoscale creep was used to detect the defect evolution dynamics at different loading rates for six metallic glasses with varying plasticity. The plastic deformation ability and the strain rate sensitivity of these metallic glasses under different loading rates were systematically investigated. Furthermore, the evolution of defect volume and relaxation time spectrum under varying loading rates was analyzed utilizing the Cooperative Shearing model in conjunction with the Maxwell-Kelvin model. It was observed that ductile and brittle metallic glasses display markedly different defect dynamics at varying loading rates. Finally, a scheme was introduced to illustrate different defect evolution paths with various loading rates for ductile and brittle metallic glasses based on their heterogeneous viscoelastic structure. The study provides insights into the differences in microscopic deformation mechanism and their structural origins in various amorphous materials.</div></div>","PeriodicalId":331,"journal":{"name":"Intermetallics","volume":"177 ","pages":"Article 108584"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of Cu on thermal and magnetocaloric properties of (GdTbHo)CoAl high-entropy metallic glasses

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-02-01 DOI: 10.1016/j.intermet.2024.108607

Z. Wang , J.Y. Ruan , F. Jin, W. Li, C.C. Yuan

(Gd_1/3Tb_1/3Ho_1/3)₅₅Co_17.5Al_27.5-xCu_x (x = 5, 10, 15, and 20) metallic glasses (MGs) with a high configurational entropy (ΔS_conf) of 1.723–1.754 R were successfully prepared by arc melting technology. Their glass-forming ability (GFA), thermodynamic behavior, and magnetocaloric effect (MCE) upon Cu addition were investigated thoroughly. Upon Cu addition, both T_g and the T_x significantly decrease with increasing 3d electron number due to the weakened f-d hybridization effect. The (Gd_1/3Tb_1/3Ho_1/3)₅₅Co_17.5Al_12.5Cu₁₅ with 15 at. % Cu exhibits a maximum value of GFA criteria, including T_rg, γ, and γ_m, as well as the lowest degree of structural order, indicating its optimal GFA, which is likely associated with the high-entropy effect and suppressed crystallization behavior. Moreover, it is found that the refrigeration capacity (RCP) also reaches a peak value of 624.83 J kg⁻¹ with a relatively larger peak magnetic entropy change (

| Δ S_{M}^{p k} |

) of 8.75 J kg⁻¹ K⁻¹ at the composition with 15 at. % Cu, accompanied by an abnormally high Curie temperature (T_C) of 59 K, which is attributed to the high experimental μ_eff of (Gd_1/3Tb_1/3Ho_1/3)₅₅Co_17.5Al_12.5Cu₁₅ as a result of the intensified magnetic interaction between rare-earth (RE) elements for alloying Cu with small size. Our work indicates that Cu is an effective element for manipulating the thermal and magnetic properties of magnetocaloric materials by influencing their microstructure, orbital hybridization effects, and magnetic exchange interactions.

{"title":"Effect of Cu on thermal and magnetocaloric properties of (GdTbHo)CoAl high-entropy metallic glasses","authors":"Z. Wang , J.Y. Ruan , F. Jin, W. Li, C.C. Yuan","doi":"10.1016/j.intermet.2024.108607","DOIUrl":"10.1016/j.intermet.2024.108607","url":null,"abstract":"<div><div>(Gd1/3Tb1/3Ho1/3)55Co17.5Al27.5-xCux (x = 5, 10, 15, and 20) metallic glasses (MGs) with a high configurational entropy (ΔSconf) of 1.723–1.754 R were successfully prepared by arc melting technology. Their glass-forming ability (GFA), thermodynamic behavior, and magnetocaloric effect (MCE) upon Cu addition were investigated thoroughly. Upon Cu addition, both Tg and the Tx significantly decrease with increasing 3d electron number due to the weakened f-d hybridization effect. The (Gd1/3Tb1/3Ho1/3)55Co17.5Al12.5Cu15 with 15 at. % Cu exhibits a maximum value of GFA criteria, including Trg, γ, and γm, as well as the lowest degree of structural order, indicating its optimal GFA, which is likely associated with the high-entropy effect and suppressed crystallization behavior. Moreover, it is found that the refrigeration capacity (RCP) also reaches a peak value of 624.83 J kg−1 with a relatively larger peak magnetic entropy change (<math><mrow><mrow><mrow><mo>|</mo><mo>Δ</mo></mrow><msubsup><mi>S</mi><mi>M</mi><mrow><mi>p</mi><mi>k</mi></mrow></msubsup></mrow><mo>|</mo></mrow></math>) of 8.75 J kg−1 K−1 at the composition with 15 at. % Cu, accompanied by an abnormally high Curie temperature (TC) of 59 K, which is attributed to the high experimental μeff of (Gd1/3Tb1/3Ho1/3)55Co17.5Al12.5Cu15 as a result of the intensified magnetic interaction between rare-earth (RE) elements for alloying Cu with small size. Our work indicates that Cu is an effective element for manipulating the thermal and magnetic properties of magnetocaloric materials by influencing their microstructure, orbital hybridization effects, and magnetic exchange interactions.</div></div>","PeriodicalId":331,"journal":{"name":"Intermetallics","volume":"177 ","pages":"Article 108607"},"PeriodicalIF":4.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Corrosion and passive behaviors of the Co-Cr-Fe-Ni-Nb eutectic high-entropy alloys in different electrolyte solutions

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-02-01 DOI: 10.1016/j.intermet.2024.108586

Fengyi Zhang , Lijun Zhang , Xueming Wei , Chunzhi Zhang , Qixiang Jia , Kai Sun , Dongtao Duan , Gong Li

The corrosion and passive behaviors of CoCrFeNiNb_x (x = 0.3, 0.45, 0.6) high-entropy alloys with eutectic microstructures were studied in different electrolyte solutions (0.6 M NaCl, 0.6 M Na₂SO₄, and 0.6 M H₂SO₄). The potentiodynamic polarisation test showed that the pitting potential of Nb0.45 alloy reached 1.084V, and the alloy had the best corrosion resistance in Na₂SO₄ solution. Mott Schottky tests and X-ray photoelectron spectroscopy tests on the Nb0.45 alloy, and it was found that different film forming mechanisms in neutral and acidic solutions. A double-layer passivation film mainly composed of Cr(OH)₃, Cr₂O₃, and Nb₂O₅ was formed. These studies provide basic theoretical reference for the preparation of new corrosion resistant high-entropy alloys.

引用次数: 0

Nanoindentation behavior of the laser-repaired CoCrFeNiV high-entropy alloy

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-02-01 DOI: 10.1016/j.intermet.2024.108585

Chao Wang , Weihai Huang , Chunxue Yi , Minqiang Jiang , Hu Huang , Jiwang Yan

High-entropy alloys (HEAs) are solid-solution alloys composed of multiple elements, exhibiting excellent mechanical properties. The unique plastic deformation mechanism induced by their specific solid solution structures has attracted considerable attention but remains incompletely understood, particularly at the micro-scale. In this study, the surface morphology, chemical composition, and microstructures of CoCrFeNiV HEA before and after laser remelting repair were investigated. Nanoindentation testing was employed to characterize the surface hardness and creep behavior of the repaired surface. The distribution of surface hardness before and after laser remelting, as well as the indentation creep behavior under different loads, were studied. The mechanism of indentation creep on the repaired surface was discussed and analyzed. The effect of microstructures of HEAs, including precipitated phases and sub-grain boundaries, on dislocation-dominated micro-scale plastic deformation was elucidated by the transmission electron microscope (TEM). This study contributes to an in-depth understanding of the creep behavior and micro-scale deformation mechanisms in HEAs.

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引用次数: 0

Interfacial reaction and IMC growth kinetics at the Bi2Te3/Ag interface during isothermal aging 等温老化过程中 Bi2Te3/Ag 界面的界面反应和 IMC 生长动力学

IF 4.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Intermetallics

Pub Date : 2025-01-31 DOI: 10.1016/j.intermet.2025.108686

Seong-Woo Pak , Hiroaki Tatsumi , Jianhao Wang , Albert T. Wu , Hiroshi Nishikawa

Bonding materials that can withstand high operating temperatures are essential for increasing the conversion efficiencies of thermoelectric power-generation devices. Sn-based solders commonly used to join thermoelectric materials and electrodes have the disadvantage of limiting the maximum operating temperature to 150 °C because of their low melting point. To overcome this limitation, in the present study, Ag nanoparticle paste with high-temperature stability, low electrical resistivity, high thermal conductivity, and printability was used for bonding a Bi₂Te₃ thermoelectric material and an electroless nickel immersion gold (ENIG)-plated Cu electrode.

We performed isothermal aging at 200 °C from 0 to 1000 h to analyze the microstructural and thickness changes in intermetallic compounds (IMCs). Initially, a heterogeneous distribution of the IMC layers was observed at the bonding interface; over time, the IMC structures became clearly distinct. The IMC thickness increased from ≤3.0 μm (initial) to 45.6 μm in 1000 h, growing by a factor of approximately 15.2. We analyzed the growth kinetics of AgTe and BiTe IMCs. The growth exponent n of the AgTe IMC was found to be 0.3, indicating grain boundary diffusion with grain-growth control, whereas the n value of the BiTe IMC was 0.5, which is consistent with volumetric diffusion-controlled growth. These differences in the growth behavior indicate that different diffusion mechanisms affect the reliability and performance of the bonding interface.

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