淬火温度对Al_(0.5)CoCrFeNiSi_(0.2)高熵合金组织结构的影响

采用真空电弧熔炼的方法制备了高熵合金Al0.5CoCrFeNiSi0.2。对其进行600℃到1100℃保温10h后淬水的淬火处理。通过金相显微镜、扫描电镜及附带的能谱仪、X射线衍射仪和透射电镜观察分析合金的组织结构。用显微硬度计测定合金的显微硬度。结果表明:铸态和淬火态的合金组织均呈典型的枝晶形貌,枝晶含有非晶相和纳米级颗粒。在淬火加热温度低于800℃时,随着淬火温度升高,晶粒细化、fcc相含量减少,硬度随淬火温度的升高而提高;当温度升高至900℃后,枝晶相长大,fcc相含量增加,大块枝晶中析出一种富含Al、Ni的θ相,硬度下降。     

Ti0.5AlCoFeNiCrx高熵合金的微观组织结构与力学性能

通过XRD分析、SEM观察和压缩实验研究了不同Cr含量对Ti0.5AlCoFeNiCrx(x为摩尔比,x=0,0.5,1,1.5,2,3)高熵合金微观组织结构与力学性能的影响。结果表明:当合金不含Cr时,呈现单一的体心立方结构;当加入Cr元素后,出现了另一种富Cr的体心立方相。随着Cr含量的增加,组织从树枝晶逐渐转变到亚共晶、共晶和过共晶组织,表明Cr能促使合金发生共晶反应。适量的Cr元素能显著提高合金的压缩力学性能,其中Ti0.5AlCoFeNiCr0.5合金具有最好的压缩强度和塑性。     

多主元高熵合金FeCoNiCuxAl微观组织结构和性能

研究了不同Cu含量的FeCoNiCuxAl高墒合金的微观引织和性能特点,（x表示摩尔比,x=0、0．5、0．8、1．0、1．5、2）,分别用X衍射、扫描电镜和维氏硬度测试Cu含量的变化对合金组织和硬度的影响。研究表明,此合金体系容易形成简单FCC结构和BCC结构的固溶体,Cu含量增加会促进FCC固溶体的形成。Ca的含量的变化对合金硬度的影响较大。随着Cu含量的增加,合金的硬度显著降低,硬度的高低主要取决于显微组织形态和体系中BCC固溶体的含量的多少。     

LaNi4-xFeCrx(x=0.2～1.0)合金的显微组织及电化学性能

研究了LaNi4-xFeCrx(x=0.2、0.4、0.6、0.8、1.0)合金中Cr替代Ni对显微组织及电化学性能的影响.研究表明,Cr的加入均使合金析出第二相,降低电化学放电容量,提高循环稳定性.合金的高倍率放电性能随x增加先增大后缓慢下降.     

铜含量对CoCrFeNi高熵合金组织结构和性能的影响

通过设计不同Cu含量的CoCrFeNi高熵合金,筛选出一种具有较高强度和导电性的Cu基高熵合金。采用X射线衍射仪、光学显微镜、扫描电子显微镜、力学性能测试机、电阻测试仪研究了铸态CoCrFeNiCux(x=1,2,3,4,5)高熵合金的组织、力学和导电性能。当x=1,2时,合金为FCC单相;当x≥3时,合金除了FCC相外还存在其他析出相。当x=1时,合金的微观形貌由等轴晶组成;当x≥1时,合金的微观形貌是树枝晶和等轴晶形貌,枝晶间的Cu含量较高。合金的拉伸强度和伸长率均随着Cu含量的升高先降低后升高,其中CoCrFeNiCu3合金的综合力学性能最差,抗拉强度仅约120 MPa,伸长率不到1%。CoCrFeNiCu5合金具有最优异的综合力学性能,其抗拉强度约为370 MPa,伸长率约为11%。合金的电阻率随着Cu含量的升高逐渐降低,CoCrFeNiCu5合金的电阻率最低,导电性能最好,同时,电阻随着温度的升高而升高。测试了5种合金的热膨胀系数,其随着Cu含量的升高呈波浪性上升。结合拉伸测试和导电性能测试结果,CoCrFeNiCu5合金具有优异的综合力学性能和导电性能。     

CoCrCu0.5FeTi0.5Alx高熵合金组织与力学性能的研究

为了研究Al含量对高熵合金CoCrCu0.5FeTi0.5Alx高熵合金组织及力学性能的影响,通过真空电弧炉熔炼CoCrCu0.5FeTi0.5Alx(x=0、0.2、0.4、0.6、0.8、1.0)高熵合金.利用X射线衍射仪测量合金的晶体结构,采用扫描电镜观察合金微观组织,利用维氏显微硬度计和万能试验机测试合金的显微...     

CuAgAlFeNi高熵合金的微观组织和性能

利用真空电弧炉熔炼CuAgAlFeNi高熵合金。分析表明:合金由FCC+BCC相组成。合金中存在的严重的密度偏析,导致合金的铸态组织分为亚共晶层和固溶体层。亚共晶层由固溶少量Al的初晶Ag和(Cu-Ag)共晶组成。固溶体层则由Al、Fe、Ni和少量Cu形成的固溶体胞晶组成,在胞晶中还存在着与亚共晶层组织相同、成分相近的"共晶球"。固溶体的硬度为HK452.2,共晶层的熔点为805℃,硬度为HK160.4。     

AlCoCrNiSi_x高熵合金微观组织结构与力学性能

通过XRD,SEM,EDS分析和显微硬度测试,系统研究了Si含量对AlCoCrNiSix高熵合金铸态组织的相结构变化、微观组织形貌特征和力学性能。结果表明:随Si含量的增加,合金相结构由单一的bcc1固溶体结构逐步转化为bcc1+bcc2结构共存,其中bcc1为AlNi基的固溶体,bcc2为CrSi固溶体。随Si含量的增加,合金的铸态组织由枝晶形态向胞状形态转变。微观组织中Al,Ni主要存在于枝晶内,Si则偏析于枝晶间。Si具有显著提高合金硬度的作用,硬度最大值达到HV991。     

La1.5Mg0.5Ni7-xCox(x=0～1.8)贮氢合金结构和电化学性能研究

La1.5Mg0.5Ni7-xCox(x=0～1.8)贮氢合金电极由高频感应熔炼加热处理制备得到.合金结构分析表明,合金主相为Ce2Ni7型结构,Mg原子分布在Ce2Ni7型单胞结构的Laves相单元中,而Co原子则分布在CaCu5单元中.随着合金中Co含量的增多,点阵参数和单胞体积呈增大趋势,氢化物变的更加稳定.合金的吸放氢平台在298K条件下介于1.01×103～1.01×104Pa之间,吸放氢滞后效应较小.合金电极的电化学分析表明合金具有390mAh/g以上的放电容量和良好的活化特性,Co元素不利于合金电极循环稳定性的改善,氢在合金中的扩散是电极反应的控制步骤.La1.5Mg0.5Ni7.0合金电极表现出较好的综合电化学性能.     

Superior mechanical properties and strengthening mechanisms of lightweight AlxCrNbVMo refractory high-entropy alloys(x = 0, 0.5,1.0) fabricated by the powder metallurgy process

Light and strong AlxCrNbVMo(x=0,0.5,and 1.0) refractory high-entropy alloys(RHEAs) were designed and fabricated via a the powder metallurgical process.The microstructure of the AlxCrNbVMo alloys consisted of a single BCC crystalline structure with a sub-micron grain size of 2-3 μm,and small amounts(4 vol.%) of fine oxide dispersoids.This homogeneous microstructure,without chemical segregation or micropores was achieved via high-energy ball milling and spark-plasma sintering.The alloys exhibited superior mechanical properties at 25 and 1000℃ compared to those of other RHEAs.Here,CrNbVMo alloy showed a yield strength of 2743 MPa at room temperature.Surprisingly,the yield strength of the CrNbVMo alloy at 1000℃ was 1513 MPa.The specific yield strength of the CrNbVMo alloy was increased by 27 % and 87 % at 25 and 1000℃,respectively,compared to the AlMo_(0.5) NbTa_(0.5)TiZr RHEA,which exhibited so far the highest specific yield strength among the cast RHEAs.The addition of Al to CrNbVMo alloy was advantageous in reducing its reduce density to below 8.0 g/cm~3,while the elastic modulus decreased due to the much lower elastic modulus of Al compared to that of the CrNbVMo alloy.Quantitative analysis of the strengthening contributions,showed that the solid solution strengthening,arising from a large misfit effect due to the size and modulus,and the high shear modulus of matrix,was revealed to predominant strengthening mechanism,accounting for over 50 % of the yield strength of the AlxCrNbVMo RHEAs.     

Microstructures and properties of high-entropy alloys

This paper reviews the recent research and development of high-entropy alloys (HEAs). HEAs are loosely defined as solid solution alloys that contain more than five principal elements in equal or near equal atomic percent (at.%). The concept of high entropy introduces a new path of developing advanced materials with unique properties, which cannot be achieved by the conventional micro-alloying approach based on only one dominant element. Up to date, many HEAs with promising properties have been reported, e.g., high wear-resistant HEAs, Co_1.5CrFeNi_1.5Ti and Al_0.2Co_1.5CrFeNi_1.5Ti alloys; high-strength body-centered-cubic (BCC) AlCoCrFeNi HEAs at room temperature, and NbMoTaV HEA at elevated temperatures. Furthermore, the general corrosion resistance of the Cu_0.5NiAlCoCrFeSi HEA is much better than that of the conventional 304-stainless steel. This paper first reviews HEA formation in relation to thermodynamics, kinetics, and processing. Physical, magnetic, chemical, and mechanical properties are then discussed. Great details are provided on the plastic deformation, fracture, and magnetization from the perspectives of crackling noise and Barkhausen noise measurements, and the analysis of serrations on stress–strain curves at specific strain rates or testing temperatures, as well as the serrations of the magnetization hysteresis loops. The comparison between conventional and high-entropy bulk metallic glasses is analyzed from the viewpoints of eutectic composition, dense atomic packing, and entropy of mixing. Glass forming ability and plastic properties of high-entropy bulk metallic glasses are also discussed. Modeling techniques applicable to HEAs are introduced and discussed, such as ab initio molecular dynamics simulations and CALPHAD modeling. Finally, future developments and potential new research directions for HEAs are proposed.     

Effect of alloying elements on microstructure,mechanical and damping properties of Cr-Mn-Fe-V-Cu high-entropy alloys

A series of new Cr-Mn-Fe-V-Cu high-entropy alloys were prepared by arc melting and suction casting. It is found that with the addition of Cu, the structure of the alloys evolved from BCC?+?BCC1 phases to BCC?+?FCC phases. With increase of Cu, the volume fraction of the Cu-Mn-rich FCC phase increased, and the morphology of the FCC phase transformed from granular particles to long strips and blocks. Compared with other reported HEAs, the Cr-Mn-Fe-V-Cu HEAs exhibit a good balance between strength and ductility. The CrMn0.3FeVCu0.06 alloy with granular FCC particles exhibits the highest compressive yield strength (1273?MPa) and excellent ductility (ε_f?=?50.7%). Quantitative calculations for different strengthening mechanisms demonstrate that dislocation and precipitate strengthening are responsible for high strength of the CrMn0.3FeVCu0.06 alloy, while the solid solution strengthening effect is very low because of its small atomic-size difference. In addition, the CrMn0.3FeVCu0.06 alloy exhibits good damping capacity due to its high dislocation and interface damping effects. Therefore, the dislocation density and distribution of FCC phase are the crucial factors for improvement of both mechanical properties and damping capacity of the HEAs.     

La0.67Mg0.33Ni3.0-xAlx(x=0～0.3)贮氢合金的相结构及电化学性能的研究

研究了Al元素对合金La0．67Mg0．33Ni3．0中Ni的替代对舍金的微观组织结构及电化学性能的影响。X射线衍射(XRD)分析结果表明La0．67Mg0．33Ni3．0合金由PuNi3型(La，Mg)Ni3相和Ce2Ni2型(La，Mg)2Ni7相组成，Al元素加入后，开始出现CaCu5型LaNi5相，随着Al含量的增加，LaNi5相逐渐增多，当x=0．3时，LaNi5相成为合金的主相，合金La0．67Mg0．33Ni3．0中Al的X荧光元素面分布图像表明了Al元素主要进入LaNi5相中，说明Al是一种LaNi5相形成元素；电化学测试表明，随着Al含量的增加，合金的最大放电容量依次下降，4种合金的最大放电量分别为392、324、267和252mAh／g，活化次数变化不大(2～3次即可活化)，循环稳定性先增加后下降。     

CeO2掺杂对AlCoCrCuFe高熵合金的组织结构与摩擦磨损性能的影响

采用熔铸法制备等摩尔比的AlCoCrCuFe高熵合金。利用X射线衍射仪、扫描电镜、能谱分析仪、显微硬度计和摩擦磨损试验机分别测试CeO2掺杂前后对其物相结构、显微组织和摩擦磨损性能的影响。结果表明:AlCoCrCuFe由BCC和FCC双相组成,合金中掺杂1%(质量分数)CeO2后引起衍射峰强度的显著提高。两种合金显微组织均为典型树枝晶,Cu与Ce元素在晶间富集,枝晶内为调幅分解组织。CeO2的加入使合金显微硬度从441.5HV增加到475.3HV,摩擦因数与质量损失率分别从0.55,1.44%降低到0.4,1.28%。     

合金V40Zr5Ti30Cr10Ni15Mox（x=0、2、4、6）的组织结构及电化学性能研究

研究了合金V40Zr5Ti30Cr10Ni15Mo x(x=0、2、4和6)的相结构及电化学性能。结果表明,所有合金均由BCC结构的V基固溶体主相和C14型Laves相组成。电化学测试结果表明,合金的放电容量随着Mo含量的增加先增大后减小。在x=2时,合金具有最大的放电容量408.3mAh/g,20次循环后容量保持率为83.2%。合金的高倍率放电性能随着Mo含量和电流密度的增加而降低,x=2时,合金的倍率放电性能最好。     

Mg-xAl-Zn(x=3,6,9)合金腐蚀行为比较研究

对不同Al含量的AZ系列镁合金(AZ31、AZ61和AZ91)在3.5%NaCl溶液中的腐蚀性能进行了比较研究,以便找到合适的耐腐蚀材料。采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)对其显微结构进行了表征。在3.5%NaCl溶液中,采用极化曲线、电化学阻抗谱(EIS)和浸泡实验对其耐腐蚀性进行了测试。结果表明,AZ系列镁合金的腐蚀行为先是点蚀,后扩展为面蚀。AZ61的极化电阻(R_P)高达288.88Ω·cm²,腐蚀电流密度低为0.0026 mA/cm²,平均腐蚀速率为2.86×10^-4 g/(h·cm²),AZ61具有更优的耐蚀性能。随着Al含量提高,镁合金的耐蚀性能先升高再降低,耐蚀性能的升高归因于β-Mg₁₇Al₁₂相的粗化和连续性。     

Microstructure and mechanical properties of FexCoCrNiMn high-entropy alloys

The microstructure and tensile properties of Fe_xCoCrNiMn high-entropy alloys (HEAs) were investigated. It was found that the Fe_xCoCrNiMn HEA has a single face-centered cubic (fcc) structure in a wide range of Fe content. Further increasing the Fe content endowed the Fe_xCoCrNiMn alloys with an fcc/body-centered cubic (bcc) dual-phase structure. The yield strength of the Fe_xCoCrNiMn HEAs slightly decreased with the increase of Fe content. An excellent combination of strength and ductility was achieved in the Fe_xCoCrNiMn HEA with higher Fe content, which can be attributed to the outstanding deformation coordination capability of the fcc/bcc dual phase structure.     

难熔高熵合金研究进展

高熵合金是近年来的新兴领域,与传统合金不同,其一般是由五种或者五种以上主要元素组成,每种主元的含量在5％～35％(原子分数)之间,多种元素混乱排列却拥有简单的相结构,高熵合金的优点显著,发展空间巨大.以难熔金属元素为基础的难熔高熵合金近年来大受关注,含有3种及以上的难熔金属组成的高熵合金称为难熔高熵合金,由于难熔金属的...