机械合金化法制备Al—Cu—Fe纳米非晶合金

采用行星式高能球磨机制备了Al80-xCuxFe20(x=20-40）三元非晶纳米合金粉末,分析了不同球磨时间及热处理工艺对粉末结构、颗粒大小等的影响。结果表明：成分为Al40Cu40Fe20的粉末球磨时逐步非晶化,球磨33h后,非晶化程度最大,最小颗粒尺寸达到5．6nm;进一步球磨,非晶晶化,颗粒尺寸增大;成分为Al80-xCuxFe20(x=20,25,30)的粉末球磨90h后,得到非晶,最小颗粒尺寸为3．4nm。球磨制备的Al-Cu-Fe非晶粉末具有铁磁性。用DSC测量了其晶化温度（Tc),Tc≈873℃。     

Al-Cu-Fe准晶薄膜/涂层的研究进展

综述了目前制备Al-Cu-Fe准晶薄膜/涂层的方法,并分析了其影响因素.重点评述了Al-Cu-Fe准晶薄膜/涂层的组织及其转变,介绍了Al-Cu-Fe准晶薄膜/涂层的性能及其应用,并指出了其今后研究趋势.     

基底材料对Al—Cu-Fe共溅射薄膜的影响

以抛光状态的纯Al、纯Cu和不同粗糙度的不锈钢基作为基底材料,采用磁控共溅射工艺来制备Al-Cu-Fe薄膜.利用原子力显微镜、能谱仪和MTS纳米力学综合测试系统分析薄膜的表面形貌、元素含量、结合强度和摩擦系数.分析结果表明:不锈钢作为基底材料的薄膜与基体的结合强度最大,其次为纯铝和纯铜.纯铜基底薄膜的摩擦系数最大,达到0.17,其余两种薄膜的摩擦系数均低于0.03.而薄膜表面形貌与基底材料的原始形貌有直接的联系,基底原始粗糙度越细小;薄膜的表面组织也细小;基底原始粗糙度越大,薄膜表面形成的晶粒的团聚越明显.这说明基底材料对薄膜的形成有重要的影响.     

Mechanical properties of quasicrystalline Al-Cu-Fe coatings with submicron-sized grains

Quasicrystalline Al-Cu-Fe coatings with submicron-sized grains (∼ 400 nm) were produced by electron beam PVD. Mechanical properties of the Al-Cu-Fe quasicrystalline coating and a bulk Al-Cu-Fe quasicrystalline specimen with an average grain size of about 50 μm were examined using a set of micro- and nanoindentation techniques (with plotting stress-strain curves). It has been found that the length of the hardening stage in the stress-strain curve at room temperature for the coating is essentially greater, and the softening is weaker as compared with those for the bulk specimen. Possible reasons for such mechanical behavior of the coatings are discussed. Nanoindentation tests have shown that stepwise plastic flow is observed in both bulk sample and coating.     

Phase Transformations in Low-Fe Alloys of the Al-Cu-Fe System

Microstructure and phase transformation in the Al-Cu-Fe alloys of the approximate compositional range of 20-50 at.% Cu and 2 - 10 Fe at.% have been investigated from samples quenched from their respective temperatures by means of different thermal analysis, magnetothermal analysis, scanning electron microscopy, electron probe analysis and powder X-ray diffraction. Representative phase transformations categorized as polymorphic, discontinuous precipitation,quasi-binary eutectoid, and ternary transitional U-type phase transformation are presented. These phase transformations were found to have a common feature which consumes the β phase and appears the φ phase. A schematic diagram was proposed to demonstrate the transition processes with decreasing temperature.     

爆炸喷涂Al-Cu-Fe准晶涂层性能分析

目的 提高准晶涂层内部准晶相含量,进而研究Al-Cu-Fe准晶涂层的各项性能。方法 采用爆炸喷涂的方式在2A12铝合金基底上制备了Al-Cu-Fe准晶涂层。借助SEM、XRD等手段对Al-Cu-Fe准晶粉体的组织形貌、物相形成进行研究。采用显微硬度计、拉力试验机测试涂层的力学性能。采用比热容测试仪、激光热导仪检测涂层的热性能。使用摩擦磨损试验仪研究了涂层的摩擦磨损性能。结果 水雾化法制成的Al-Cu-Fe准晶粉体主要包含准晶相和少量的β-Al_42.54Cu_34.65Fe_22.81相,准晶含量为73%。882℃为准晶相的熔点,粉体在800℃的退火温度下准晶含量能达到98.7%。涂层在700℃下比热容为0.749 J/(g·K),热导率为5.913W/(m·K)。涂层的显微硬度为569.4HV0.3,经退火处理最高硬度可达658.33HV0.3。涂层的结合强度为33.25 MPa,退火处理后结合强度为58.75 MPa。涂层在不同载荷和温度下,摩擦因数为0.768～0.512(均低于基体),在15 N和20 N的载荷下磨损率...     

Particle size effects on chemistry and structure of Al-Cu-Fe quasicrystalline coatings

Gas atomized Al₆₃Cu₂₅Fe₁₂ powders of varying size fractions were plasma sprayed onto hot (~600 °C) and cool (~25 °C) substrates using Mach I and subsonic plasma gun configurations. The chemical composition and phase contents of coatings were determined. Furthermore, coatings were annealed in vacuum at 700 °C for 2 h to observe phase changes. It was found that finer particles (e.g., <25 μm) tend to vaporize Al during spraying, which shifts the coating composition away from the quasicrystalline (ψ) single-phase region in the Al-Cu-Fe phase diagram. Coatings deposited on hot substrates were denser, richer in theψ phase, and harder than the corresponding coatings deposited onto cool substrates.     

机械合金化Al-Cu-Fe准晶相形成的研究进展

综述了机械合金化A1-Cu-Fe准晶相的形成机理及热力学稳定性方面的研究进展.     

Al-Cu-Fe系初生准晶相凝固过程的热力学分析

采用XRD,SEM和TEM等方法,研究了铸态 Al58.8Cu36.6Fe3.5Si1.1合金(973K保温2.5h后水淬)的显微组织及相组成.观察到铸态样品中存在4种不同的相,即初生准晶I相、Φ相、θ-Al2Cu相和η-AlCu相.对准晶I相及其晶体近似相R相,提出相应的自由能计算模型及算法,从理论上说明准晶(Al61.89Cu25.61Fe11.10)I相是高温稳定相,当温度低于938K时,将形成其晶体近似相R相.     

Al-Cu-Fe准晶及其晶体类似相与纯Mg的界面反应

分析了按照Al63Cu25Fe12配比常规凝固制备的AlCuFe准晶材料的相组成, 研究了块状AlCuFe准晶材料与熔融纯镁的界面反应,发现在界面处存在物质交换作用. 镁与AlCuFe准晶材料有良好的浸润性, 这归因于准晶材料中孔隙的存在、亚稳相的分解和表面氧化层与Mg的反应.     

Structure and properties of mechanically alloyed composite materials Al/Al-Cu-Fe quasicrystal

The structure and properties of metal-matrix Al/Al-Cu-Fe-quasicrystal composites produced by compacting mechanically alloyed powders have been studied. An increase in the time of mechanical alloying was found to lead to an increase in the microhardness. Compression tests showed that the failure of samples occurred via the intense formation of cracks along the direction parallel to the applied stresses; the ultimate strength increases with increasing time of mechanical alloying. As the compacting temperature increases, the ultimate strength remains unchanged to temperatures of 300–400°C; at higher temperatures, a marked increase in the ultimate compression strength is observed. An increase in the compacting temperature leads to an improvement of frictional characteristic of samples.     

Effect of grain size on the damping capacity of quasicrystalline Al-Cu-Fe materials

Thick quasicrystalline (QC) Al-Cu-Fe coatings obtained by electron-beam physical vapour deposition (EB-PVD) on titanium substrates at different temperatures have been used for damping measurements. The measurements were performed by the method of free-decay vibrations with using flat cantilever specimens covered with the QC coatings in the strain amplitude range of 10^− 4-10^− 3 and in the temperature range of 290-620 K. We have studied the intrinsic damping capacity of the QC coatings with different grain sizes as a function of strain amplitude using a calculation procedure. The intrinsic damping capacity of all the QC materials is found to increase progressively with temperature in the whole strain amplitude range. It was found that decreasing of the QC grain size to nanoscale values leads to a significant increase of their damping capacity at temperatures above 520 K. Possible mechanisms of dissipation of mechanical energy in nanostructured quasicrystals at elevated temperatures are discussed.     

Structural phase transformations in quasicrystal-forming Al-Cu-Fe alloys and defects of the icosahedral phase

Transmission electron microscopy was used to investigate structural and phase transformations and defects of the icosahedral (ι) phase that is formed upon isothermal annealings (T _ann = 550–700°C) of quenched quasicrystal-forming alloys Al₆₁Cu₂₆Fe₁₃ and Al₆₃Cu₂₅Fe₁₂ (β solid solution + ι phase). It has been established that in the Al₆₃Cu₂₅Fe₁₂ alloy there occurs a reversible ι-R-approximant transformation, whereas in the Al₆₁Cu₂₆Fe₁₃ alloy there is formed a single-phase ι structure with regions with a high density of randomly distributed planar defects (T _ann = 550°C), which are partially annealed at 650°C. The observed defects are, mainly, ultrathin interlayers (“intergrowths” to 3–5 nm in thickness) on quasicrystal planes with A5_ι axes with an imperfect decagonal structure. As the basic mechanism, the growth mechanism of the formation of defects during the β → i transformation is proposed. The role of the alloy composition and low-temperature β → 3C-phase transformation in the realization of this mechanism is discussed.     

热处理工艺对超音速火焰喷涂Al-Cu-Fe准晶涂层性能影响

目的 使用超音速火焰喷涂(HVOF)方法制备Al-Cu-Fe准晶涂层,研究热处理温度对涂层中准晶相含量和性能的影响以及封孔处理对涂层耐蚀性的改善。方法 以304不锈钢为基体和真空雾化Al-Cu-Fe准晶粉末为热喷涂材料,采用超音速火焰喷涂方法制备准晶涂层,并进行550～700℃热处理。利用透射电镜、扫描电镜、光学显微镜、能谱分析仪和X射线衍射仪分析准晶粉末和涂层的衍射花样、微观形貌、成分和相结构。分别使用显微硬度仪和电化学工作站对比测量304不锈钢和准晶涂层的硬度和耐蚀性能。结果 粉末中二十面体准晶相(I相)为主相,并伴生准晶类似相(β相)。经过超音速火焰喷涂后,涂层中I相和β相的含量分别为78.7%和21.3%,相组成与原始粉末接近。550℃和600℃热处理1h后,涂层中β相消失,I相占比进一步上升,并伴随Al₂Cu(θ相)产生。随着热处理温度继续升高至650℃,β相开始重新析出;当热处理温度升至700℃,β相占比增至13.5%。热处理后准晶涂层的最高硬度为674HV,为304不锈钢硬度(182HV)的3.7倍。准晶涂层经过热处理和表面封孔后,其在3.5%NaC...     

Effect of starting powders on the control of microstructural development of Al-Cu-Fe quasi-crystalline plasma-sprayed coatings

Powders and plasma-sprayed coatings of an Al₆₃Cu₂₅Fe₁₂ alloy containing a quasi-crystalline phase were characterized by X-ray diffraction, electron microscopy, and differential thermal analysis. The relationships between powder and coating microstructures were examined. Powders were produced by casting and crushing and by gas atomization. Both techniques produced powders with multiple phases; cubic and monoclinic ternary structures were formed along with the face-centered icosahedral quasi-crystalline phase. These phases were also produced in the plasma-arc-sprayed coatings formed using different starting powders. Cooling rates during powder processing greatly affected the phase equilibria and scale of segregation of this alloy. Finer grain sizes in the plasma-sprayed coatings were obtained from the more chemically homogeneous gas-atomized powders.     

Effect of the addition of crystalline β-phase in Al-Cu-Fe quasicrystalline coatings on their tribological properties

We investigate tribological properties (friction coefficient, wear, and adhesion force with fretting tests) of both quasicrystalline (Ψ-phase) and dual-phase (Ψ + β-cubic phases) Al-Cu-Fe coatings produced by electron-beam physical vapour deposition. Performed standard pin-on-disk tests (using bear steel pin and a load of 2 N) indicate that both quasicrystalline and dual-phase (Ψ + β) Al-Cu-Fe coatings exhibit close values of the friction coefficient (≈ 0.2-0.3) in vacuum. At the same time, the wear rate of the dual-phase coating is found to be essentially lower than that of quasicrystalline coating. It is demonstrated also that the value of the adhesion between the coating and the steel counterpart under fretting depends on the coating structure. The lowest adhesion is found to be observed for quasicrystalline coatings. Possible origins of the tribological behaviour of the coatings and their potential applications are discussed.     

Corrosion Behavior of Ψ and β Quasicrystalline Al-Cu-Fe Alloy

Two nanostructured Al-Cu-Fe alloys, Al₆₄Cu₂₄Fe₁₂ and Al_62.5Cu_25.2Fe_12.3, have been studied. Icosahedral quasicrystalline (ψ) Al₆₄Cu₂₄Fe₁₂ and crystalline cubic (β) Al_62.5Cu_25.2Fe_12.3 cylindrical ingots were first produced using normal casting techniques. High-energy mechanical milling was then conducted to obtain ψ icosahedral and β intermetallic nanostructured powders. Electrochemical impedance spectroscopy, linear polarization resistance, and potentiodynamic polarization were used to investigate the electrochemical corrosion characteristics of the powders in solutions with different pH values. Current density (i _corr), polarization resistance (R _p), and impedance modulus (|Z|) were determined. The results showed that regardless of pH value, increasing the solution temperature enhanced the corrosion resistance of the both phases. However, the electrochemical behavior of the ψ phase indicated that its stability depends on the submerged exposure time in neutral and alkaline environments. This behavior was related to the type of corrosion products present on the surfaces of the particles along with the diffusion and charge-transfer mechanisms of the corrosion process.     

Main features and the driving force for the formation of the quasicrystalline phase in Al-Cu-Fe powders after mechanoactivation

The evolution of the phase and structural states during heating of a powder mixture of composition Al₆₅Cu₂₃Fe₁₂ subjected to mechanoactivation has been investigated. The solid-state transformations have been studied using Mössbauer spectroscopy, X-ray diffraction, and differential scanning calorimetry. The sequence of phase formation during heating was compared with the data on the heat of formation of binary solutions and compounds in the system. The analysis performed showed that the nature of transformations in the process of the formation of the quasicrystalline phase was caused by the thermodynamic parameters of the system.     

Evaluation of the mechanical properties of conventionally-cast Al matrix composites reinforced by quasicrystalline Al-Cu-Fe particles using continuous ball indentation technique

Room temperature mechanical properties of the Al/(AlCuFe)_p and Al₉₆Cu₄/(AlCuFe)_p cast composites were estimated from uniaxial compressive test and continuous ball indentation technique. Values of the Young’s modulus and yield stress determined from continuous ball indentation tests were slightly overestimated, suggesting a surface effect on the mechanical properties. However, it was shown that the Al-Cu-Fe particles provided a significant increase of the elastic modulus, yield stress, and strain hardening, especially in the range up to 10% volume fraction of reinforcements. Also, determination of the hardness by continuous-ball-indentation tests revealed a strong influence of the matrix strength on the mechanical properties of the conventionally cast composites.