Ti含量对氩弧熔覆CoCrFeNiCuTix高熵合金涂层组织及性能的影响

采用氩弧熔覆技术在Q235钢基体表面制备了CoCrFeNiCuTi_x(x表示摩尔比值,x=0、0.3、0.5、0.8和1)高熵合金涂层,研究了Ti含量对CoCrFeNiCuTi_x高熵合金微观结构和力学性能的影响。结果表明,不同Ti含量的CoCrFeNiCuTi_x高熵合金均为FCC单相固溶体。CoCrFeNiCu合金的微观组织为柱状晶结构。随着Ti的加入,微观组织中开始出现析出相,且Ti含量越高,析出相越多。同时Ti的加入明显提高了合金的显微硬度,当Ti的摩尔比为1时,涂层的截面显微硬度值达到最高值439.54 HV0.1。Ti对CoCrFeNiCuTi_x高熵合金的耐磨性具有显著影响,CoCrFeNiCuTi合金表现出最好的耐磨性。随着Ti含量的升高,合金的磨损机理由黏着磨损转化成黏着磨损与氧化磨损并存。     

Si含量对WMoNbCrTi高熵合金微观组织和力学性能的影响

WMoNbCrTi高熵合金是一种极具应用潜力的高温结构材料，添加Si有望提高其综合力学性能。以高能球磨粉末为原料，采用放电等离子烧结技术制备了WMoNbCrTiSi_x(x=0、0.1、0.25和0.5)高熵合金，研究Si含量对其微观组织和力学性能的影响。结果表明：加入Si后高熵合金的组织由BCC固溶体、Laves相和硅化物组成。当x=0.1时，Si主要形成Ti₅Si₃,当x=0.25时，大部分Si与Ti形成Ti₅Si₃,少部分Si与Nb形成Nb₃Si,当x=0.5时，Si主要形成Ti₅Si₃、Nb₃Si和Cr₃Si。当x从0增加到0.5时，WMoNbCrTiSi_x高熵合金的硬度由9.84 GPa增加到13.46 GPa,断裂韧性从6.68 MPa·m^1/2下降到4.72 MPa·m^1/2。WMoNbCrT...     

AlCr1.3TiNi2共晶高熵合金的高温摩擦学性能及磨损机理

采用电磁悬浮熔炼+直接铸造的方法制备了千克级的AlCr_1.3TiNi₂共晶高熵合金,借助TEM、APT等表征手段分析了该合金的微观组织与成分分布,使用HT-1000摩擦试验机对比研究了该合金与GH4169镍基高温合金的高温摩擦学性能。结果表明：该共晶高熵合金具有超细的层片状共晶组织(层片间距约350 nm),其共晶两相为晶格错配度只有约2%的bcc相与L2₁相,L2₁相中还存在大量的纳米析出相;≤600℃时,共晶高熵合金的磨损机理以磨粒磨损为主,其磨损率均低于GH4169合金;800℃时,共晶高熵合金的磨痕表面塑性变形加剧,其摩擦系数明显高于GH4169合金,但2者的磨损率相差不大。GH4169合金高温耐磨性的提高得益于其磨损表面氧化物膜的形成,而共晶高熵合金出色的耐磨性主要与其良好的高温组织稳定性及力学性能有关。     

退火温度对FeMoCrVTiSix高熵合金组织及力学性能的影响

在400、600、800、1100 ℃下对FeMoCrVTiSi_x(x=0、0.3)进行退火处理,利用X射线衍射仪、扫描电镜、差热扫描分析仪、显微硬度计、万能试验机等探究了不同退火温度对合金的组织和力学性能的影响。结果表明,Si元素的添加提高了FeMoCrVTi高熵合金的热稳定性。经过退火处理,FeMoCrVTiSi_x高熵合金的微观组织仍为以BCC固溶相为主的枝晶结构,但在枝晶边缘出现黑色的细小富Ti相,其含量随着退火温度的增加而增多,在1100 ℃下富Ti相回溶。富Ti相的析出提高了合金的硬度,其中,800 ℃退火后试样的硬度达到最大值,FeMoCrVTi试样的硬度达到932 HV0.2,FeMoCrVTiSi_0.3的硬度达到998 HV0.2。     

盐浴渗氮处理对FeCrMnNiAl0.2Ti0.1高熵合金组织及性能的影响

采用盐浴渗氮的化学热处理方法对FeCrMnNiAl_0.2Ti_0.1高熵合金进行表面强化,主要工艺为预热+盐浴渗氮+氧化,研究渗氮温度对渗层和性能的影响。采用光学显微镜、扫描电镜、X射线衍射仪研究不同渗氮温度下高熵合金的组织结构和物相,利用显微硬度计和W-2000摩擦磨损试验机分别测量硬度和耐磨性。结果表明,经过盐浴渗氮后,高熵合金表面形成含氮化物和氧化物的复合渗层,渗氮层深度最高为27.1 μm,硬度最高可达1080.0 HV0.2。盐浴渗氮可以有效提高高熵合金的耐磨性,改善摩擦学行为,640 ℃渗氮试样的磨损率仅为0.025 mm³/(N·m),与铸态相比降低了约76.7%。     

Mo元素含量对FeAlCuCrNiMox系高熵合金组织结构及性能的影响

为了研究Mo元素对FeAlCuCrNiMo_x系高熵合金的组织结构及性能的影响,将FeAlCuCrNiMo_x系高熵合金粉末制备成药芯焊丝,并用气体保护堆焊到45钢表面制备出FeAlCuCrNiMo_x系高熵合金,而后对堆焊层进行硬度、显微组织、物相组成及耐蚀性能分析. 结果表明,FeCuCrAlNiMo_x系堆焊高熵合金呈现单一的AlFe固溶体,晶格结构为体心立方. 当x = 0.8时,合金堆焊层的晶粒尺寸最为细小,晶界强化明显,硬度最高,平均硬度达到47.8 HRC,磨损量最小,为0.08 g. 加入一定量的Mo元素之后腐蚀电位降低,即耐腐蚀性能下降.     

Zr-0.7Sn-0.35Nb-0.3Fe-xGe合金在高温高压LiOH水溶液中耐腐蚀性能的研究

利用静态高压釜腐蚀实验研究了Zr-0.7Sn-0.35Nb-0.3Fe-xGe（x=0.05,0.1,0.2,质量分数,%）系列合金在360℃/18.6 MPa/0.01 mol/L LiOH水溶液中的耐腐蚀性能;利用TEM和SEM分别观察了合金基体的显微组织和氧化膜的显微组织.结果表明:Ge可以显著改善Zr-0.7Sn-0.35Nb-0.3Fe合金在高温高压LiOH水溶液中的耐腐蚀性能,当Ge含量为0.1%时,合金的耐腐蚀性能最佳.在Zr-0.7Sn-0.35Nb-0.3Fe-xGe系列合金中发现尺寸较小的hcp结构的Zr（Fe,Cr,Nb）₂型、Zr（Fe,Cr,Nb,Ge）₂型第二相和尺寸较大的四方结构的Zr₃Ge型第二相.腐蚀220 d的Zr-0.7Sn-0.35Nb-0.3Fe-0.1Ge合金氧化膜致密,厚度较薄,几乎没有微孔隙和微裂纹,ZrO₂柱状晶较多.这说明添加适量的Ge不仅可以有效延缓氧化膜中空位扩散凝聚形成微孔隙和微孔隙发展形成微裂纹的过程,还可以延迟ZrO₂由柱状晶向等轴晶的演化,从而改善合金的耐腐蚀性能.     

退火温度对CrFeCoNiTi1.5高熵合金微结构与性能的影响

为研究中低温热处理对CrFeCoNiTi_1.5高熵合金性能的影响,分别在200、400及600 ℃下对高熵合金进行10 h退火处理。通过X射线衍射仪、扫描电镜(SEM)、能谱仪(EDS)、显微硬度计和电化学工作站对高熵合金的组织结构、表面形貌以及元素的偏析程度进行分析,并测试了高熵合金的动电位极化曲线以及维氏硬度。结果表明:退火温度的提高有利于CrFeCoNiTi_1.5高熵合金中HCP结构相的析出;随着温度的升高Cr、Fe、Co和Ni逐渐向晶内聚集分布,Ti逐渐向晶间聚集。600 ℃中低温退火处理时合金耐腐蚀性能最好,硬度为914 HV0.5。     

Ti对单相FCC的CoCrNi体系中/高熵合金组织与性能的影响

在CoCrNi三元、CoCrFeNi四元和Al_0.3CoCrFeNi五元合金中分别添加0.1～0.5(摩尔比)Ti，通过真空电弧炉制备出高硬度和高压缩强度的中/高熵CoCrNiTi_x、CoCrFeNiTi_x和Al_0.3CoCrFeNiTi_x合金棒材。Ti添加量为0.1的合金棒材(以下简称Ti_0.1合金，其余合金作相同处理)均保持单相FCC结构；Ti_0.3合金均出现少量的新相(η或R);CoCrNiTi_0.5合金由FCC+BCC+η+σ相组成，Al_0.3CoCrFeNiTi_0.5合金由FCC+BCC+R+B₂相组成，且二者微观组织均呈“花朵”状；而CoCrFeNiTi_0.5合金则由FCC+Laves+R+σ相组成，为树枝晶状结构。随着Ti含量的增加，三种体系合金的硬度均逐渐提高，且提高幅度按CoCrNiTi_x     

激光熔覆CoCrFeNiSix高熵合金涂层组织及耐蚀性能研究

目的 研究Si含量对CoCrFeNi系高熵合金涂层组织、物相、显微硬度及耐蚀性能的影响.方法 通过激光熔覆技术在45钢基材上制备CoCrFeNiSix(x为物质的量之比,x=0.0,0.5,1.0,1.5,2.0)高熵合金涂层,使用扫描电镜、X射线衍射仪、显微硬度仪、电化学工作站对涂层的显微组织、物相组成、显微硬度、耐蚀性能、腐蚀形貌进行分析研究.结果 CoCrFeNi高熵合金涂层为单一的fcc相,之后随着Si含量的提升,涂层向bcc相转变,当x=2.0时,全部转化为bcc相.涂层的微观组织以等轴晶与枝晶为主,当Si含量较少时,Si元素主要在晶界中偏析,随着Si含量的增加,过多的Si会固溶到晶粒内部.涂层的平均显微硬度随着Si含量的升高而增加,CoCrFeNiSi2.0可达到566.5HV0.5.在3.5％NaCl溶液中,涂层的腐蚀电位随Si含量的增加而变大,CoCrFeNiSi2.0较CoCrFeNiSi0.0的腐蚀电位正移约160 mV,腐蚀电流密度从1.17×10-6 A/cm2减小到6.06×10-7 A/cm2,耐蚀性提高.当Si含量较低时,涂层表面出现连续大面积腐蚀痕迹,随着Si含量的增加,表面腐蚀以点蚀为主.结论 在CoCrFeNi系高熵合金涂层中添加Si元素,可以促进bcc相的生成,提高涂层的显微硬度,同时可以有效抑制合金涂层的腐蚀倾向,以及减缓合金涂层的腐蚀速率,提高耐蚀性能.     

Microstructure and properties of Al0.3CrFe1.5MnNi0.5Ti x and Al0.3CrFe1.5MnNi0.5Si x high-entropy alloys

In this article, the microstructure, hardness, and corrosion resistance of the Al0.3CrFe1.5MnNi0.5Tixand Al0.3CrFe1.5MnNi0.5Six(x = 0, 0.2, 0.5, 1.0) high-entropy alloys were investigated via X-ray diffraction(XRD)scanning electron microscopy(SEM), digital display Vickers hardness tester, and electrochemical technique These alloys are mainly composed of BCC solid-solution structure. When adding high content of Ti or Si elemen(x C 0.5), some intermetallic compounds are found in the microstructure, which makes the alloys have a high hardness, high brittleness, and easy cracking. While the alloys with low content of Ti or Si(x = 0.2) have a hardness of HV 420–HV 430, and its hardness increases about 14 %compared with that of Al0.3CrFe1.5MnNi0.5. Electrochemical results in 3.5 % NaCl solution show that the alloying elements Ti and Si have a negative influence on the corrosion resistance of the Al0.3CrFe1.5MnNi0.5alloys.     

Affordable FeCrNiMnCu high entropy alloys with excellent comprehensive tensile properties

Fe_0.4Cr_0.4NiMn_xCu (0 ≤ x ≤ 1.4) high entropy alloys (HEAs) were prepared by copper-mold casting. The phase selection, microstructure, tensile properties and fracture morphologies were investigated. The microstructure with dual FCC phases was formed in the as-cast HEAs with x ≤ 1, and BCC phase was crystallized from the central FCC dendrites of HEAs with x = 1.2 and 1.4. In homogenized Fe_0.4Cr_0.4NiMnCu HEA, needle-like shaped BCC phase was formed resulting in a slight enhancement of yield strength. Compositional heterogeneity was detected in both FCC and BCC dendrites. These HEAs exhibit excellent comprehensive tensile properties, e.g. the yield strength, ultimate strength and elongation of the HEA with x = 1 reaches 439 MPa, 884 MPa and 23.4%, respectively. High density of dislocations in FCC matrix was formed after tensile deformation. FCC type of fine polyhedra, which is mainly composed of Cr, Mn and O, is formed in dendrites. In this work, the phase selection and strengthening mechanism were evaluated based on atomic size factor. It was found that two criteria can be employed to predict the phase regions of current alloys. The solid solution strengthening for this HEA system is the most important among the four kinds of strengthening mechanisms.     

Microstructure,anticorrosion, biocompatibility and antibacterial activities of extruded Mg−Zn−Mn strengthened with Ca

To find suitable biodegradable materials for implant applications, Mg?6Zn?0.3Mn?xCa (x=0, 0.2 and 0.5, wt.%) alloys were prepared by semi-continuous casting followed by hot-extrusion technique. The microstructure and mechanical properties of Mg?6Zn?0.3Mn?xCa alloys were investigated using the optical microscope, scanning electron microscope and tensile testing. Results indicated that minor Ca addition can slightly refine grains of the extruded Mg?6Zn?0.3Mn alloy and improve its strength. When 0.2 wt.% and 0.5 wt.% Ca were added, the grain sizes of the as-extruded alloys were refined from 4.8 to 4.6 and 4.2 μm, respectively. Of the three alloys studied, the alloy with 0.5 wt.% Ca exhibits better combined mechanical properties with the ultimate tensile strength and elongation of 334 MPa and 20.3%. The corrosion behaviour, cell viability and antibacterial activities of alloys studied were also evaluated. Increasing Ca content deteriorates the corrosion resistance of alloys due to the increase of amount of effective cathodic sites caused by the formation of more Ca₂Mg₆Zn₃ phases. Cytotoxicity evaluation with L929 cells shows higher cell viability of the Mg?6Zn?0.3Mn?0.5Ca alloy compared to Mg?6Zn?0.3Mn and Mg?6Zn?0.3Mn? 0.2Ca alloys. The antibacterial activity against Staphylococcus aureus is enhanced with increasing the Ca content due to its physicochemical and biological performance in bone repairing process.     

Aluminum Alloying Effects on Lattice Types, Microstructures, and Mechanical Behavior of High-Entropy Alloys Systems

The crystal lattice type is one of the dominant factors for controlling the mechanical behavior of high-entropy alloys (HEAs). For example, the yield strength at room temperature varies from 300 MPa for the face-centered-cubic (fcc) structured alloys, such as the CoCrCuFeNiTi _x system, to about 3,000 MPa for the body-centered-cubic (bcc) structured alloys, such as the AlCoCrFeNiTi _x system. The values of Vickers hardness range from 100 to 900, depending on lattice types and microstructures. As in conventional alloys with one or two principal elements, the addition of minor alloying elements to HEAs can further alter their mechanical properties, such as strength, plasticity, hardness, etc. Excessive alloying may even result in the change of lattice types of HEAs. In this report, we first review alloying effects on lattice types and properties of HEAs in five Al-containing HEA systems: Al _x CoCrCuFeNi, Al _x CoCrFeNi, Al _x CrFe_1.5MnNi_0.5, Al _x CoCrFeNiTi, and Al _x CrCuFeNi₂. It is found that Al acts as a strong bcc stabilizer, and its addition enhances the strength of the alloy at the cost of reduced ductility. The origins of such effects are then qualitatively discussed from the viewpoints of lattice-strain energies and electronic bonds. Quantification of the interaction between Al and 3d transition metals in fcc, bcc, and intermetallic compounds is illustrated in the thermodynamic modeling using the CALculation of PHAse Diagram method.     

机械合金化联合真空热压烧结工艺制备CoCrFeNi高熵合金的力学性能和耐腐蚀性能

采用机械合金化和真空热压烧结工艺制备了CoCrFeNi高熵合金。采用X射线衍射仪、扫描电子显微镜、电感耦合等离子体发射光谱和光学显微镜对产物的相结构和微观结构进行了表征,并采用万能试验机、维氏硬度计和电化学工作站对其力学性能和耐腐蚀性能进行了研究。结果表明：与电化学还原联合热压烧结工艺以及电弧熔炼法制备的CoCrFeNi高熵合金性能相比,机械合金化联合真空热压烧结工艺制备的CoCrFeNi高熵合金具有良好的抗拉伸强度和断裂伸长率,其合金硬度是电弧熔炼法制备合金的2倍,在0.5 mol/L H₂SO₄、1 mol/L KOH和3.5%（质量分数）NaCl水溶液中,该合金具有与304不锈钢及电化学还原联合热压烧结工艺或电弧熔炼法制备的合金相当的耐腐蚀性能。     

Influence of Si and Ti contents on the microstructure, microhardness and performance of TiAlSi intermetallics in Al-Si-Ti alloys

In this study, the influence of Si and Ti contents on the microstructure, microhardness and morphology of TiAlSi intermetallics in ternary Al-Si-Ti alloys was investigated. The increase of Si addition in Al-xSi-2Ti alloys leads to an increase of Si content in TiAlSi phase as well as an increase of microhardness. A phase evolution from Ti(Al_1−xSi_x)₃ to Ti₇Al₅Si₁₂ at about 14 wt.% Si was detected, while all the TiAlSi intermetallics exhibit flake-like. The increase of Ti content promotes the morphological transformation of TiAlSi from flake-like to block-like and primary Si particles are replaced by blocky TiAlSi particles in hypereutectic Al-Si alloy. The high-temperature strengthening effect of TiAlSi particles in a piston alloy was investigated and the strength is increased by 11.9% in this article, while the elongation and yield strength are increased by 17.6% and 10.1%, respectively.     

Alloy Design and Properties Optimization of High-Entropy Alloys

This article reviews the recent work on the high-entropy alloys (HEAs) in our group and others. HEAs usually contain five or more elements, and thus, the phase diagram of HEAs is often not available to be used to design the alloys. We have proposed that the parameters of ?? and ?? can be used to predict the phase formation of HEAs, namely ??????1.1 and ??????6.6%, which are required to form solid-solution phases. To test this criterion, alloys of TiZrNbMoV _x and CoCrFeNiAlNb _x were prepared. Their microstructures mainly consist of simple body-centered cubic solid solutions at low Nb contents. TiZrNbMoV _x alloys possess excellent mechanical properties. Bridgman solidification was also used to control the microstructure of the CoCrFeNiAl alloy, and its plasticity was improved to be about 30%. To our surprise, the CoCrFeNiAl HEAs exhibit no apparent ductile-to-brittle transition even when the temperatures are lowered from 298?K to 77?K.     

Effect of the aluminium content of AlxCrFe1.5MnNi0.5 high-entropy alloys on the corrosion behaviour in aqueous environments

High-entropy alloys (HEAs) are a newly developed family of multi-component alloys. The potentiodynamic polarization and electrochemical impedance spectroscopy of the Al_xCrFe_1.5MnNi_0.5 alloys, obtained in H₂SO₄ and NaCl solutions, clearly revealed that the corrosion resistance increases as the concentration of aluminium decreases. The Al_xCrFe_1.5MnNi_0.5 alloys exhibited a wide passive region, which extended >1000 mV in acidic environments. The Nyquist plots of the Al-containing alloys had two capacitive loops, which represented the electrical double layer and the adsorptive layer. SEM micrographs revealed that the general and pitting corrosion susceptibility of the HEAs increased as the amount of aluminium in the alloy increased.     

Effects of Ti-addition on the characteristics of wear resistant Al-Si-Fe base alloys processed via rapid solidification

Rapidly solidified Al-Si-Fe base alloys were prepared by gas atomization, hot pressing and extrusion. To optimize wear resistance and mechanical properties, Al-20 wt.%Si-5 wt.%Fe base alloys containing 1–3 wt.%Ti were newly designed and characterized in detail. The additions of Ti (especially, ~2 wt.%Ti) effectively increased the wear resistance and mechanical properties such as tensile strength and hardness; however, the addition of 3 wt.%Ti was not desirable because of the precipitation of the primary Ti₇Al₅Si₁₂ phase in the as-quenched state. Based on TEM analyses, the improved properties in the Al-Si-Fe alloys containing Ti were found to be due to the formation of the (Al, Si)₃Ti phase finely dispersed in the matrix. ASCM16CE is the gas atomized and consolidated composite including 3 wt.% of SiC particles (reference alloy).     

Phase Evolution and Mechanical Properties of AlCoCrFeNiSi<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> High-Entropy Alloys Synthesized by Mechanical Alloying and Spark Plasma Sintering

In the current investigation, AlCoCrFeNiSi_x (x?=?0, 0.3, 0.6 and 0.9 in atomic ratio) high-entropy alloy systems are prepared by mechanical alloying and subsequently consolidated by spark plasma sintering. The microstructural and mechanical properties were analyzed to understand the effect of Si addition in AlCoCrFeNi alloy. The x-ray diffraction analysis reveals the supersaturated solid solution of the body-centered cubic structure after 20 h of ball milling. However, the consolidation promotes the transformation of body-centered phases partially into the face-centered cubic structure and sigma phases. A recently proposed geometric model based on the atomic stress theory has been extended for the first time to classify single phase and multi-phases on the high-entropy alloys prepared by mechanical alloying and spark plasma sintering process. Improved microhardness and better wear resistance were achieved as the Si content increased from 0 to 0.9 in the present high-entropy alloy.