Al_xFeCoCrNiCu(x=0.25、0.5、1.0)高熵合金的组织结构和电化学性能研究

研究了不同Al含量AlxFeCoCrNiCu(x=0.25、0.5、1)高熵合金的组织结构,探讨了Al含量对合金电化学性能的影响,并与304不锈钢进行对比。结果表明,制备的高熵合金晶体结构由简单的FCC结构转为FCC和有序BCC结构。与此同时,随着Al含量的增加,合金的硬度越大,从165HV提高到485HV。极化曲线表明,在0.5mol/L H2SO4溶液和1mol/L NaCl溶液中,高熵合金和304不锈钢相比,Al0.5FeCoCrNiCu合金表现出较好耐腐蚀性和抗孔蚀能力。     

C元素对Ni_(68.6)Cr_(8.7)Nb_3P_((16.5-x))B_(3.2)C_x非晶合金性能的影响

研究了C的添加对Ni_(68.6)Cr_(8.7)Nb_3P_((16.5-x))B_(3.2)C_x(x=0,0.1,0.3,0.5,0.7,1,%,原子分数)合金的非晶形成能力、热稳定性和腐蚀性能的影响。研究表明,x=0.5时,合金棒为非晶结构,直径达2 mm;适量C的添加提高了Ni基非晶合金的热稳定性能;在1 mol/L H_2SO_4溶液环境下,随C含量的增加,Ni基非晶合金薄带的耐腐蚀性能逐渐增强。     

Cr对FeCoNiAlCrx高熵合金组织与力学性能的影响

采用真空电弧熔炼法制备FeCoNiAlCr_x(x=0,0.2,0.4,0.6,0.8,原子比，下同)高熵合金铸锭，探究Cr含量对该合金微观结构、组织及力学性能的影响。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)对合金相结构、微观组织及成分进行分析表征；采用万能试验机对合金压缩性能进行测试。结果表明：随着Cr含量的增加，合金的微观结构由单相BCC结构转变为BCC+FCC混合结构；合金微观组织由等轴晶逐步转变为树枝晶，并且合金晶粒尺寸发生了明显细化。本实验制备的五种合金都具有较好的力学性能，合金的抗压强度随着Cr含量的增加大幅度增强，当x=0时合金抗压强度和塑性应变最低，分别为1500 MPa和13.56%;当x=0.8时，合金抗压强度和塑性应变达到最大，分别为2460 MPa和30.09%;合金抗压强度的增幅达64%。这表明Cr添加对FeCoNiAlCr_x高熵合金的组织细化、抗压强度和塑性的提升具有重要作用。     

退火温度对CoCrCu0.5FeTi0.5Alx高熵合金微观组织与耐腐蚀性能的影响

为了研究不同退火温度对CoCrCu_0.5FeTi_0.5Al_x高熵合金性能的影响,通过真空电弧熔炼CoCrCu_0.5FeTi_0.5Al_x(x=0、0.4、0.8)高熵合金并使用真空管式炉进行600,800,1 000℃退火实验。使用XRD测试合金的晶体结构,采用SEM观察合金微观组织,利用维氏显微硬度计和电化学工作站测试高熵合金的显微硬度和耐腐蚀性能。结果表明,退火后的高熵合金出现新的Laves相,合金相主要由FCC、BCC和Laves相混合组成。在CoCrCu_0.5FeTi_0.5Al_x(x=0、0.4、0.8)高熵合金中,x=0.4的硬度在600℃退火状态下达到最大值为883.15HV。1 000℃退火下的CoCrCu_0.5FeTi_0.5Al_0.4耐腐蚀性能达到最优,腐蚀电压和腐蚀电流密度分别为-0.396 V和6.800×1...     

Zr元素对AlFeCrCoCuZr_x高熵合金组织及腐蚀性能的影响

对铸态AlFeCrCoCuZr_x(x=0,0.5,1)多组元高熵合金的微观组织、硬度及其在3.5%NaCl溶液中的耐腐蚀性能进行了研究。研究表明:合金微观组织为典型的树枝晶结构,随着Zr元素的加入,枝晶由单一的BCC相转变为由两相组成,而枝晶间由富Cu的FCC相组成并保持不变。合金硬度随Zr元素的增加而提高,AlFeCrCoCuZr合金的硬度达到698HV。合金在3.5%NaCl溶液中的耐蚀性能均优于304L不锈钢,但随着Zr含量的增加,合金的耐蚀性降低。     

Al含量对CrFeNiAlxSi系高熵合金性能的影响

选取与天然铬铁矿粉有效成分相近的Al、Cr、Fe、Ni、Si元素为高熵合金成分,采用激光烧结技术制备CrFeNiAl_xSi系高熵合金,研究了Al含量对CrFeNiAl_xSi系高熵合金的物相结构、显微组织、密度和孔隙率、显微硬度、耐磨和抗高温氧化性能的影响。结果表明：CrFeNiAl_xSi(x=0.2、0.4、0.6、0.8、1.0)系高熵合金由BCC+FCC相构成,随着Al含量的提高FCC相减少;x=0.6的合金硬度最高,为813.3HV;合金的密度降低孔隙率提高,x=0.2的合金密度最大,为4.21 g·cm^-³,孔隙率最低,为26.46%;x=0.6的合金耐磨性能最佳,磨损率为69.50 mg·cm^-²;随着Al含量的提高,合金的抗高温氧化性能明显提高。     

铝材表面激光熔覆Ni_(1.5)Co_(1.5)FeCrTi_x高熵合金层的组织与性能

为了提高铝合金的耐磨性及耐蚀性并降低高熵合金中元素偏析的现象,采用CO_2激光熔覆技术在铝基体表面制备了Ni_(1.5)Co_(1.5)FeCrTi_x高熵合金熔覆层。借助光学显微镜、扫描电镜、X射线衍射仪和电化学工作站检测技术研究了Ti含量对Ni_(1.5)Co_(1.5)FeCrTi_x熔覆层显微组织和耐蚀性能的影响。结果表明:Ni_(1.5)Co_(1.5)FeCrTi_x高熵合金熔覆层主要相结构为简单的面心立方相、金属间化合物相和Laves相;当Ti含量摩尔比从0.5增至2.0时,Ni_(1.5)Co_(1.5)FeCrTi_x高熵合金熔覆层的表面硬度从510 HV增加到554 HV,在0.5 mol/L HNO_3溶液中具有优异的耐蚀性能。     

Mo含量对CoCrFeNiMo高熵合金组织及耐蚀性能的影响

高熵合金由于具有优异的机械性能及耐蚀性能在涂层工业领域备受关注。采用同步送粉激光熔覆技术在Q235钢表面制备了CoCrFeNiMo_x高熵合金涂层,研究了涂层的组织结构和耐蚀性能,并结合第一性原理计算分析了涂层耐蚀机理。研究结果表明：CoCrFeNiMo_0.1、CoCrFeNiMo_0.2高熵合金涂层是由fcc相组成,而CoCrFeNiMo_0.3高熵合金涂层则由fcc相和σ相组成。合金的晶粒主要呈树枝晶,枝晶间富集Cr、Mo元素,枝晶内富集Co、Fe元素。在3.5%(质量分数)NaCl溶液中,CoCrFeNiMo_x高熵合金涂层具有优良的综合耐蚀性能;并且随着Mo元素含量的增加,涂层的腐蚀电位正移,腐蚀电流密度减少,钝化区间变长,阻抗弧半径增大,电极反应阻力增强。通过第一性原理计算证明,涂层较高的耐蚀性能与表面致密的钝化膜形成密切相关。     

微量W元素的添加对CoCrFeNiMnAl高熵合金的组织与性能的影响EI北大核心CSCD

高熵合金(HEAs)表现出比传统合金更为优异的耐磨耐蚀性能,逐渐成为金属材料领域的研究热点。采用金属热还原法制备不同W含量的CoCrFeNiMnAlW_(x)(x=0.12,0.15,0.19)高熵合金,研究微量W元素的添加对CoCrFeNiMnAlW_(x)高熵合金的相结构、微观组织与性能的影响。采用XRD,SEM和EDS等技术表征该合金的相结构、显微组织及元素分布,利用材料表面性能测试仪和电化学工作站测定该合金的摩擦磨损性能和电化学腐蚀性能。结果表明:不同W含量高熵合金均由两种不同晶格常数的BCC相组成,随着W含量的增加,BCC1相微观相貌并没有明显的变化,但是BCC2相的微观形貌和元素分布随W含量的变化而明显变化,而耐磨损性能和耐腐蚀性能均有一定程度的提高,CoCrFeNiMnAlW_(0.19)合金的摩擦因数和磨损率分别为0.684和1.06×10^(-5)mm^(3)/(N·m),磨损机制由黏着磨损转变为黏着磨损和磨粒磨损相结合,最后再转变为摩擦磨损;在3.5%NaCl溶液中的腐蚀电流密度从6.08×10^(-6)A/cm^(2)减小到1.72×10^(-6)A/cm^(2),腐蚀速率也逐渐减小。     

非晶合金颗粒／树脂基复合材料的耐蚀性

采用内旋转溶液法制备非晶态Fe_(76)Cr_4P_(13)C_7合金粉末,在其中加入适量的合成树脂,压制成形,制备非晶合金颗粒/树脂基复合材料。研究了复合材料在1N H_2SO_4,1N HCl,1N H_2SO_4+0.5N NaCl,1N NaOH和3.5％NaCl溶液中的耐蚀性。实验结果表明:复合材料在试验介质中具有优异的耐蚀性。在非晶态合金粉末中加入合成树脂,压制成形,可以获得耐蚀的块体材料,具有工业应用价值。     

Influence of disorder on electronic structure and magnetic properties in Fe-rich Fe–Si alloys

We present the results of ab initio calculations of the spin-polarized electronic structure of disordered bcc and fcc Fe_1 − xSi_x alloys from dilute solid solutions of Si on iron up to FeSi intermetallic compound composition (x=0.01..0.5) and ordered intermetallic phases FeSi in B20 structure and Fe₃Si in DO₃ structure. The self-consistent calculations were performed with the coherent potential approximation within the Korringa–Kohn–Rostoker method (KKR–CPA) for disordered case and by using the tight-binding linear muffin–tin orbital (TB LMTO) method for intermetallic compounds. In the last case the supercell approach has been utilized in order to take into account the structural defects for this ordered phase. In particular, we have performed a series of calculations in the BCC Fe_1 − xSi_x alloys with x=0.01, 0.015, 0.1, 0.15, 0.25.     

镍氢电池负极材料V2Ti0.5Cr0.5Ni1-xMox(x=0.02~0.08)的结构和电化学性能

为了改善镍氢电池负极材料的循环稳定性能, 采用真空感应电弧熔炼炉制备了V₂Ti_0.5Cr_0.5Ni_1-xMo_x (x=0.02~0.08)合金, 分析了不同含量的Mo替代Ni之后对合金电极的组织结构及电化学性能的影响。研究结果表明, 电极材料主要由BCC结构的V基固溶体主相和TiNi二次相组成, 随着合金中Mo替代Ni含量x由0.02增加到0.08, 合金电极的放电容量先增加后降低, 合金电极的循环稳定性能以及电化学动力学性能先得到改善而后降低, 合金电极的综合性能均在x=0.04时达到最好。     

Mechanical,corrosion and magnetic behavior of a CoFeMn1.2NiGa0.8 high entropy alloy

In this study,a magnetic high entropy alloy (HEA) of CoFeMn1.2NiGa0.8 was designed and prepared by arc melting in order to investigate its mechanical,corrosion and magnetic behavior.The results show that the alloy mainly possesses body-centered cubic (BCC) phase and face-centered cubic (FCC) phase.A high compressive strength of 1450 MPa,a strain of 18.5 ％ and a relatively low yield strength of 303 MPa in as-cast condition at room temperature can be achieved in the present alloy.In-situ high-energy X-ray diffraction technique was employed to reveal the deformation mechanism of CoFeMn1.2NiGa0.8 under uniaxial compression and the results show that the competition between BCC phase and FCC phase plays a significant role during the compressive process.The corrosion behavior of CoFeMn1.2NiGa0.8 was investigated in 3.5 wt％ NaCl solution and it turned out that the alloy possessed good corrosion resistance.At last,the magnetic behavior of the CoFeMn1.2NiGa0.8 alloy was studied and it can present a high saturation magnetization of 94.5 emu/g and a coercivity of 26.4Oe at 4 K.This work indicates that the present CoFeMn1.2NiGa0.8 HEA has promising applications as future magnetic functional materials.     

Microstructure and corrosion behaviour of FeCoNiCuSnx high entropy alloys

Abstract

The FeCoNiCuSn_x alloys with different Sn contents are prepared, the microstructure and the corrosion behaviour of the alloys are investigated. When Sn content is lower than 0.09, FeCoNiCuSn_x alloys consist of a single FCC phase. While Sn content of the alloy is 0.09, a small quantity of BCC structure is present. The FeCoNiCuSn_x alloys have a wider passive region in the NaOH solution. FeCoNiCuSn_x alloys exhibit a better corrosion resistance in NaCl solution than 304 stainless steel, the corrosion resistance of FeCoNiCuSn_0.04 alloy is best among all the alloys. The corrosion resistance of FeCoNiCuSn_x alloys in NaOH solution is lower than that of 304 stainless steel, the corrosion resistance of FeCoNiCuSn_0.03 alloy is best among all FeCoNiCuSn_x alloys.     

Pyroelectric properties of BST/PLT composite thick films with addition of xPbO–(1 − x)B2O3 glass

The Ba_xSr_1−xTiO₃ (BST)/Pb_1−xLa_xTiO₃ (PLT) composite thick films (20 μm) with 12 mol% amount of xPbO–(1 − x)B₂O₃ glass additives (x = 0.2, 0.35, 0.5, 0.65 and 0.8) have been prepared by screen-printing the paste onto the alumina substrates with silver bottom electrode. X-ray diffraction (XRD), scanning electron microscope (SEM) and an impedance analyzer and an electrometer were used to analyze the phase structures, morphologies and dielectric and pyroelectric properties of the composite thick films, respectively. The wetting and infiltration of the liquid phase on the particles results in the densification of the composite thick films sintered at 750 °C. Nice porous structure formed in the composite thick films with xPbO–(1 − x)B₂O₃ glass as the PbO content (x) is 0.5 ≥ x ≥ 0.35, while dense structure formed in these thick films as the PbO content (x) is 0.8 ≥ x ≥ 0.65. The volatilization of the PbO in PLT and the interdiffusion between the PLT and the glass lead to the reduction of the c-axis of the PLT phase. The operating temperature range of our composite thick films is 0–200 °C. At room temperature (20 °C), the BST/PLT composite thick films with 0.35PbO–0.65B₂O₃ glass additives provided low heat capacity and good pyroelectric figure-of-merit because of their porous structure. The pyroelectric coefficient and figure-of-merit F_D are 364 μC/(m² K) and 14.3 μPa^−1/2, respectively. These good pyroelectric properties as well as being able to produce low-cost devices make this kind of thick films a promising candidate for high-performance pyroelectric applications.     

Morphological changes induced by thermal anneals in NiFe/Ag multilayers; their relation to the resistive and magnetoresistive properties

(Ti, Al)N films have drawn much attention as alternatives for TiN coatings, which are oxidized easily in air above 500 °C. We have investigated the effect of Al content on the oxidation resistance of (Ti_{1 − x}Al_x)N films prepared by r.f. reactive sputtering.

(Ti_{1 − x}Al_xN films (O ≤ x ≤ 0.55) were deposited onto fused quartz substrates by r.f. reactive sputtering. Composite targets with five kinds of Al-to-Ti area ratio were used. The sputtering gas was Ar (purity, 5 N) and N₂ (5 N). The flow rate of Ar and N₂ gas was kept constant at 0.8 and 1.2 sccm, respectively, resulting in a sputtering pressure of 0.4 Pa. The r.f. power was 300 W for all experiments. Substrates were not intentionally heated during deposition. The deposited films (thickness, 300 nm) were annealed in air at 600 900 °C and then subjected to X-ray diffractometer and Auger depth profiling.

The as-deposited (Ti_{1 − x}Al_x)N films had the same crystal structure as TiN (NaCl type). Al atoms seemed to substitute for Ti in lattice sites. The preferential orientation of the films changed with the Al content of the film, x. Oxide layers of the films grew during annealing and became thicker as the annealing temperature increased. The thickness of the oxide layer grown on the film surface decreased with increasing Al content in the film. For high Al content films an Al-rich oxide layer was grown on the surface, which seemed to prevent further oxidation. All of the films, however, were oxidized by 900 °C annealing, even if the Al content was increased up to 0.55.     

Optical transitions near the band edge in bulk CuInxGa1−xSe2 from ellipsometric measurements

From the analysis of the variation of optical absorption coefficient with incident photon energy between 0.8 and 2.6 eV, obtained from ellipsometric data, the energy E_G of the fundamental absorption edge and E_G′ of the forbidden direct transition for CuIn_xGa_1−xSe₂ alloys are estimated. The change in E_G and the spin-orbit splitting Δ_SO=E_G′−E_G with the composition x can be represented by parabolic expression of the form E_G(x)=E_G(0)+ax+bx² and Δ_SO(x)=Δ_SO(0)+a′x+b′x², respectively. b and b′ are called “bowing parameters”. Theoretical fit gives a=0.875 eV, b=0.198 eV, a′=0.341 eV and b′=−0.431 eV. The positive sign of b and negative sign of b′ are in agreement with the theoretical prediction of Wei and Zunger [Phys. Rev. B 39 (1989) 6279].