Plasma cladding was used to prepare a CoCrFeMnNi high-entropy alloy(HEA)coating under different conditions.The process parameters were optimized using an orthogonal experiment design based on surface morphology qualit...Plasma cladding was used to prepare a CoCrFeMnNi high-entropy alloy(HEA)coating under different conditions.The process parameters were optimized using an orthogonal experiment design based on surface morphology quality characteristics,dilution rate,and hardness.The optimal process parameters were determined through range and variance analysis to be a cladding current of 70 A,a cladding speed of 7 cm·min^(-1),and a powder gas flow rate of 8 L·s^(-1).During the optimized experiments,both the cladded and annealed CoCrFeMnNi HEA coatings exhibit some pores,micro-voids,and a small amount of aggregation.However,the aggregation in the annealed coating is more dispersed than that in the cladded coating.The cladded CoCrFeMnNi HEA coating consists of simple FCC phases,while a new Cr-rich phase precipitates from the FCC matrix after annealing the coating at a temperature range of 550°C-950°C.After annealing at 850°C,the proportion of the FCC phase decreases compared to the cladded coating,and the number of large-angle grain boundaries is significantly reduced.However,the proportion of grains with sizes below 50μm increases from 61.7%to 74.3%.The micro-hardness and wear resistance of the cladded coating initially increases but then decreases with an increase in annealing temperature,indicating that appropriate annealing can significantly improve the mechanical properties of the CoCrFeMnNi HEA coatings by plasma cladding.The micro-hardness of the CoCrFeMnNi HEA coatings after annealing at 650°C increases to 274.82 HV_(0.2),while the friction coefficient decreases to below 0.595.展开更多
用固态扩散方法实现了CoCrFeMnNi高熵合金与铜在温度750~850℃下的良好连接,利用扫描电镜(Scanning electron microscope,SEM)、能谱(Energy disperse spectroscopy,EDS)分析、显微硬度测试及拉伸试验研究扩散反应温度对其界面反应行为...用固态扩散方法实现了CoCrFeMnNi高熵合金与铜在温度750~850℃下的良好连接,利用扫描电镜(Scanning electron microscope,SEM)、能谱(Energy disperse spectroscopy,EDS)分析、显微硬度测试及拉伸试验研究扩散反应温度对其界面反应行为和接头力学性能的影响,结合菲克扩散第二定律计算和分析Cu原子在高熵合金中的扩散系数。结果表明:Cu在高熵合金一侧的扩散速率大于高熵合金组元在Cu侧的扩散,随温度增加,高熵合金组元向Cu侧扩散时其在扩散区内原子浓度分布降低的程度按Mn>Cr>Fe>Co>Ni的顺序依次减小。理论计算表明,Cu在高熵合金中的平均扩散系数明显小于铜在不锈钢中的平均扩散系数。经扩散反应后,Cu/高熵合金界面附近均可形成FCC型固溶体组织的反应层,无金属间化合物产生。所有扩散连接接头拉伸后其断裂均发生在远离界面的铜侧,随扩散焊温度升高,其抗拉强度和应变有所降低,其中750℃时铜的抗拉强度与应变分别达到最大值224MPa和33%。展开更多
通过制备Co Cr Fe Mn Ni X（X=V,Ti,Si,Zr）高熵合金,研究了原子尺寸差异δ与合金的组织、相结构和磨损性能之间的关系。研究结果表明：随着δ值增大,合金的XRD衍射强度逐渐降低,合金由FCC单相结构过渡到FCC＋BCC双相结构;随着δ值的增...通过制备Co Cr Fe Mn Ni X（X=V,Ti,Si,Zr）高熵合金,研究了原子尺寸差异δ与合金的组织、相结构和磨损性能之间的关系。研究结果表明：随着δ值增大,合金的XRD衍射强度逐渐降低,合金由FCC单相结构过渡到FCC＋BCC双相结构;随着δ值的增大,对应合金的摩擦因数降低,硬度和磨损性能提高。当δ值大于11.40%时,合金的显微组织、相结构、硬度和磨损性能均发生显著变化,δ=11.40%为Co Cr Fe Mn Ni X高熵合金组织和性能发生突变的阈值。展开更多
Quasi-equiatomic Co Cr Fe Mn Ni high entropy alloy(HEA)has been in-situ alloyed by selective laser melting(SLM)from a blend of Co Cr Fe Ni pre-alloyed powder and Mn elemental powder.The blended powder shows good print...Quasi-equiatomic Co Cr Fe Mn Ni high entropy alloy(HEA)has been in-situ alloyed by selective laser melting(SLM)from a blend of Co Cr Fe Ni pre-alloyed powder and Mn elemental powder.The blended powder shows good printability with various SLM parameters and the as-built HEA samples achieve a reliable forming quality.Despite the slight evaporation of Mn,energy dispersive spectrometer mapping and Xray diffraction results show that the as-built HEA has a homogeneous chemical distribution and presents a single face-centred-cubic(fcc)phase,indicating successful in-situ alloying.The study has verified the feasibility of using blended powder to prepare high-quality HEA by SLM.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(No.51861025)the Jiangxi Provincial Department of Science and Technology(No.20203BDH80W008).
文摘Plasma cladding was used to prepare a CoCrFeMnNi high-entropy alloy(HEA)coating under different conditions.The process parameters were optimized using an orthogonal experiment design based on surface morphology quality characteristics,dilution rate,and hardness.The optimal process parameters were determined through range and variance analysis to be a cladding current of 70 A,a cladding speed of 7 cm·min^(-1),and a powder gas flow rate of 8 L·s^(-1).During the optimized experiments,both the cladded and annealed CoCrFeMnNi HEA coatings exhibit some pores,micro-voids,and a small amount of aggregation.However,the aggregation in the annealed coating is more dispersed than that in the cladded coating.The cladded CoCrFeMnNi HEA coating consists of simple FCC phases,while a new Cr-rich phase precipitates from the FCC matrix after annealing the coating at a temperature range of 550°C-950°C.After annealing at 850°C,the proportion of the FCC phase decreases compared to the cladded coating,and the number of large-angle grain boundaries is significantly reduced.However,the proportion of grains with sizes below 50μm increases from 61.7%to 74.3%.The micro-hardness and wear resistance of the cladded coating initially increases but then decreases with an increase in annealing temperature,indicating that appropriate annealing can significantly improve the mechanical properties of the CoCrFeMnNi HEA coatings by plasma cladding.The micro-hardness of the CoCrFeMnNi HEA coatings after annealing at 650°C increases to 274.82 HV_(0.2),while the friction coefficient decreases to below 0.595.
文摘用固态扩散方法实现了CoCrFeMnNi高熵合金与铜在温度750~850℃下的良好连接,利用扫描电镜(Scanning electron microscope,SEM)、能谱(Energy disperse spectroscopy,EDS)分析、显微硬度测试及拉伸试验研究扩散反应温度对其界面反应行为和接头力学性能的影响,结合菲克扩散第二定律计算和分析Cu原子在高熵合金中的扩散系数。结果表明:Cu在高熵合金一侧的扩散速率大于高熵合金组元在Cu侧的扩散,随温度增加,高熵合金组元向Cu侧扩散时其在扩散区内原子浓度分布降低的程度按Mn>Cr>Fe>Co>Ni的顺序依次减小。理论计算表明,Cu在高熵合金中的平均扩散系数明显小于铜在不锈钢中的平均扩散系数。经扩散反应后,Cu/高熵合金界面附近均可形成FCC型固溶体组织的反应层,无金属间化合物产生。所有扩散连接接头拉伸后其断裂均发生在远离界面的铜侧,随扩散焊温度升高,其抗拉强度和应变有所降低,其中750℃时铜的抗拉强度与应变分别达到最大值224MPa和33%。
文摘通过制备Co Cr Fe Mn Ni X（X=V,Ti,Si,Zr）高熵合金,研究了原子尺寸差异δ与合金的组织、相结构和磨损性能之间的关系。研究结果表明：随着δ值增大,合金的XRD衍射强度逐渐降低,合金由FCC单相结构过渡到FCC＋BCC双相结构;随着δ值的增大,对应合金的摩擦因数降低,硬度和磨损性能提高。当δ值大于11.40%时,合金的显微组织、相结构、硬度和磨损性能均发生显著变化,δ=11.40%为Co Cr Fe Mn Ni X高熵合金组织和性能发生突变的阈值。
基金supported financially by the Shenzhen ScienceandTechnologyInnovationCommission(Nos.ZDSYS201703031748354 and JCYJ20170817110358927)the Science and Technology Planning Project of Guangdong Province of China(No.2017B090911003)the Natural Science Foundation of Guangdong Province(No.2016A030313756)。
文摘Quasi-equiatomic Co Cr Fe Mn Ni high entropy alloy(HEA)has been in-situ alloyed by selective laser melting(SLM)from a blend of Co Cr Fe Ni pre-alloyed powder and Mn elemental powder.The blended powder shows good printability with various SLM parameters and the as-built HEA samples achieve a reliable forming quality.Despite the slight evaporation of Mn,energy dispersive spectrometer mapping and Xray diffraction results show that the as-built HEA has a homogeneous chemical distribution and presents a single face-centred-cubic(fcc)phase,indicating successful in-situ alloying.The study has verified the feasibility of using blended powder to prepare high-quality HEA by SLM.
