| 引用本文: | 陈晨,安煜东,姚宏伟,蒲吉斌.Cr/Fe含量对AlCoCrFeNi2.1共晶高熵合金微观组织和腐蚀性能的影响[J].中国表面工程,2024,37(6):343~353 |
| CHEN Chen,AN Yudong,YAO Hongwei,PU Jibin.Effect of Cr / Fe on the Microstructure and Corrosion Behaviors of AlCoCrFeNi2.1 Eutectic High-entropy Alloy[J].China Surface Engineering,2024,37(6):343~353 |
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| 摘要: |
| AlCoCrFeNi2.1共晶高熵合金由面心立方无序固溶体相（FCC）和体心立方有序相（B2）形成交替片层结构，具有良好的铸造性能和强韧性。然而，在 NaCl 溶液电化学腐蚀过程中，B2 相的富 Al 钝化膜比 FCC 相的富 Cr 钝化膜稳定性差，导致 B2 相较快溶解，发生局部腐蚀。通过相图计算法（CALPHAD）设计 AlCoCr1+xFe1?xNi2.1高熵合金，通过提高 Cr / Fe 元素比来调控合金的微观组织和耐腐蚀性能。与铸态 AlCoCrFeNi2.1合金相比，铸态 AlCoCr1.5Fe0.5Ni2.1合金中硬质 B2 / BCC 双相的体积分数由 27.2%提升至 42.6%，其中体心立方结构（BCC）富 Cr 纳米相的体积分数为 19.8%，其维氏显微硬度提高了 8.6%， 在 3.5wt.% NaCl 溶液中的腐蚀电流密度降低了 35.5%。因此，通过成分设计在贫 Cr 的 B2 相中大量析出富 Cr 共格纳米相， 实现硬度和耐腐蚀性能的协同提升。研究成果为高强度与耐腐蚀一体化高熵合金的开发提供了新策略。 |
| 关键词: 高熵合金 相形成 微观组织 硬度 电化学腐蚀 |
| DOI：10.11933/j.issn.1007-9289.20231229002 |
| 分类号:TG174 |
| 基金项目:国家杰出青年科学基金（52325503）；宁波市自然科学基金一般项目（2023J328） |
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| Effect of Cr / Fe on the Microstructure and Corrosion Behaviors of AlCoCrFeNi2.1 Eutectic High-entropy Alloy |
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CHEN Chen1，2，AN Yudong2，YAO Hongwei2，3，PU Jibin2，3
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1.School of Materials Science and Engineering, Taiyuan University of Science and Technology,Taiyuan 030024 , China ；2.Key Laboratory of Advanced Marine Materials, Ningbo Institute of Materials Technology andEngineering, Chinese Academy of Sciences, Ningbo 315201 , China ；3.Qianwan Institute of CNITECH, Ningbo 315336 , China
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| Abstract: |
| In recent years, high-entropy alloys (HEAs) have attracted considerable attention owing to their outstanding properties and distinctive design concepts of multiple principal elements. HEAs often crystallize into simple structures, including face-centred-cubic (FCC) and body-centred-cubic (BCC). However, HEAs with single-phase FCC structures exhibit higher ductility but lower strength, whereas those with single-phase BCC structures tend to exhibit limited ductility. To simultaneously achieve high strength and good ductility, the concept of eutectic high-entropy alloys (EHEAs) has been proposed. The AlCoCrFeNi2.1 EHEA demonstrated exceptional strength-ductility correlation and castability owing to its complete lamellar eutectic structure, which consisted of a soft FCC phase and a hard B2 phase. Notably, eutectic crystallization resulted in an uneven distribution of elements in the AlCoCrFeNi2.1 EHEA. Specifically, Cr was enriched in the FCC phase, and Al was enriched in the B2 phase. While both Al and Cr are prone to form a compact oxide film, the Al-rich passivation film of the B2 phase is less stable than the Cr-rich passivation film of the FCC phase during electrochemical corrosion in NaCl solution. This led to local corrosion in the B2 phase. Numerous studies have shown that Cr in the Al-Co-Cr-Fe-Ni HEA system tends to be distributed in both the FCC and BCC phases. Therefore, an increase in Cr can promote the formation of a Cr-rich BCC phase, which can form a dense passivation film, thereby improving corrosion resistance. In this study, the effects of Cr and Fe on the microstructural evolution and corrosion performance of the AlCoCrFeNi2.1 EHEA were systematically investigated. As-cast AlCoCr1+xFe1?xNi2.1 (x = 0, 0.3, 0.5) alloys were designed using the calculation of phase diagrams (CALPHAD). The ingots were synthesized by vacuum arc melting of the raw elements (with a weight percentage purity≥99.9%) under an argon atmosphere. The crystal structures of the as-cast alloys were characterized using an X-ray diffractometer (XRD). The microstructure and chemical composition were examined using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The Vickers hardness was measured using a Vickers microhardness tester. Electrochemical measurements were performed using an electrochemical workstation in 3.5 wt.% NaCl solution at room temperature. The electrochemical tests used a three-electrode system, where the working electrode was the test sample, the reference electrode was a saturated calomel electrode (SCE), and a Pt plate was the counter electrode. The results indicate that as the Cr / Fe ratio increased, the alloys gradually transformed from a regular lamellar eutectic structure to a meta-eutectic structure. For AlCoCrFeNi2.1, AlCoCr1.3Fe0.7Ni2.1 and AlCoCr1.5Fe0.5Ni2.1, the volume fractions of the FCC phase were 72.8%, 68.3% and 57.4%, respectively; those of the B2 phase were 27.2%, 23.6% and 22.8%, respectively; and those of the Cr-rich BCC nanoparticles were 0%, 8.1% and 19.8%, respectively. The trend of changes in the volume fractions of each phase was consistent with the results of the CALPHAD simulation calculati?瑮桳攮?晍潯牲浥慯瑶楥潲測?潴晨??牤?牳楴捲桩?灵慴獩獯楮瘠慣瑯楥潦湦?晣楩汥浮獴?漠湯?????慨渠摥??汭?牮楴挠桧?灡慤獵獡楬癬慹琠楴潥湮?晥楤氠浴獯?潡湲??㈱?牦敲杯業漠湤獩??瑥桲敳物敯扮礬?楡浮灤爠潴癨楥渠杤?瑳桴敲?换潵牴物潯獮椠潣湯?灦敦物晣潩牥浮慴渠捯敦?潃晲?瑤桥散?慥污汳潥祤???祯?搠攲献椲朠湩楮渠杴?瑥栠敁?捃潯浃灲潆獥楎瑩椼潳湵?琾漲?昱愼振楳汵楢琾愠瑡敬?瑯桹攠?灯爠攱挮椵瀠楩瑮愠瑴楨潥渠?潬晃??牲?牳極换栾?挮漵格支牳敵湢琾?湥愼湳潵灢栾愰献攵猼?楳湵?琾桎敩??牵?瀾漲漮爱????灢栾愠獡敬??慹?猠祍湥敡牮杷楨獩瑬楥挬?整湨桥愠湖捩散浫敥湲瑳?業湩?桲慯牨摡湲敤獮獥?慳渠摧?捡潤牵牡潬獬楹漠湩?牣敲獥楡獳瑥慤渠捦敲?睭愠猲?愱挮根椱攠癴敯搠??吷栮椰猵?晈楖渠摡楳渠杴?灥爠潶癯楬摵敭獥?慦?湡潣癴敩汯?猠瑯牦愠瑴敨来礠?晲漭牲?瑣桨攠?摃敃瘠敮污潮灯浰敡湲瑴?潣晬?桳椠杩桮?獲瑥牡敳湥杤琠桡?捤漠牴牨潡獴椠潯湦?牴敨獥椠獆瑃慃渠瑰????猠?ecreased. As the Cr / Fe ratio increased, the corrosion potentials (Ecorr) of the three alloys changed slightly. This indicated that the corrosion tendencies of the three alloys were similar. However, the corrosion current density of the AlCoCr1.5Fe0.5Ni2.1 alloy was reduced by 35.5% (from 0.203 5 to 0.131 3 μA·cm?2 ) compared to the AlCoCrFeNi2.1 alloy in a 3.5 wt.% NaCl solution at room temperature. Furthermore, all the curves in the Nyquist plot consist of a semicircular arc, indicating that the dissolution kinetics of the passive film are governed by the charge transfer mechanism on the nonuniform surface. The semicircle radius increased, suggesting an incremental improvement in the corrosion resistance with increasing Cr / Fe ratio. A larger impedance modulus in the low-frequency range corresponds to a higher impedance value and a greater hindrance to charge transfer, ultimately indicating better corrosion resistance. The phase angles of the three alloys remained relatively stable in the midto low-frequency region, with a phase angle close to 80°based on the Porter phase frequency diagram. At 10?2 Hz, the phase angle of AlCoCr1.3Fe0.7Ni2.1 alloy and AlCoCr1.5Fe0.5Ni2.1 alloy decreased slightly, indicating that their corrosion resistance was superior to that of AlCoCrFeNi2.1 alloy. During the electrochemical corrosion process in a 3.5 wt.% NaCl solution, the dispersed precipitation of Cr-rich BCC nanoparticles promoted |
| Key words: high-entropy alloy phase formation microstructure hardness electrochemical corrosion |
