Development and production of amorphous and nanocrystalline materials

The authors of this article were awarded a Gold Medal at the international exhibition Metal-Expo 2005 for the development and production of amorphous and nanocrystalline materials. The article presents characteristics of mass-produced amorphous and nanocrystalline alloys developed by specialists at the Central Research Institute of Ferrous Metallurgy for use in the electrical and electronics industries. __________ Translated from Metallurg, No. 4, pp. 76–78, April, 2006.     

Reaction of iron-based magnetically soft materials with glass enamels

We have studied the reaction of M45 and SK20 glass enamels with PZhR3 iron and an iron — phosphorus alloy containing 0.8 mass% phosphorus using the “sessile” drop method in the temperature range 1000– 1300°C. We have established that when the M45 glass enamel reacts with the iron, then oxides of alkali metals Mg and Na oxidize it to Fe₂O₃ . The iron in the contact zone of the iron — SK20 glass enamel system is oxidized by zinc oxide, while the iron oxide formed dissolves in the glass enamel. Adhesion of the SK20 glass enamel to the iron surface is significantly better than in the Fe - M45 system. The best adhesion properties are observed in the iron-phosphorus alloy — SK20 glass enamel system, due to the more vigorous reaction between the components.     

块体纳米软磁材料的研究现状

介绍了国内外块体纳米软磁材料的发展和应用情况。对块体纳米软磁材料的制备方法、纳米晶的形成机理、优异软磁性能的根源进行了探讨。阐述了未来块体纳米软磁材料的研究方向。     

Structure and properties of submicrocrystalline and nanocrystalline copper produced by dynamic channel angular pressing

The evolution of the structure of 99.8%-pure copper during severe plastic deformation by dynamic channel angular pressing and the properties of the produced submicro- and nanocrystalline (SMC + NC) copper have been studied. It is shown that four-pass extrusion forms a copper structure under conditions of repeated processes of fragmentation and dynamic recrystallization. It is found that copper with a mixed nonequilibrium SMC + NC structure consisting of 50–350 nm grains/subgrains exhibits high mechanical properties (HV 1560 MPa, σ_u = 440 MPa, σ_0.2 = 414 MPa, δ = 19%) and is thermally stable on heating to 150°C.     

Effect of impurities in iron powders on the physical properties of sintered magnetically soft materials

The effect of impurities in the iron powder on the physical properties of sintered magnetically soft materials was studied. Although vanadium increased the coercive force, it improved properties such as the saturation magnetization, specific electrical resistance, and hardness. The coercive force and bend strength of the powder materials were linearly dependent on the amount of carbide-forming elements. Phosphorous decreased this undersirable effect. Increasing the fraction of carbide forming elements in the materials decreased their densities, and increased their specific electrical resistances, phosphorous being unable to change this dependence.     

Magnetoimpedance, magnetoinductance and AC magnetoresistance studies on amorphous and nanocrystalline ribbons

A systematic investigation of the influence of Al and V on the magnetoimpedance (MI), magnetoinductance (mi) and AC Magnetoresistance (ACMR) effect in melt-spun Fe_73.5Si_13.5B₈CuNb_(3?x)V_xAl (x=0,1,1.5,3) ribbons has been performed in the frequency range 500 kHz — 13 MHz and under dc magnetic field (H _ext ) up to 60 Oe. Nanocrystals of α-FeSi were observed, when annealed at 500°C in vaccum. MI, mi and ACMR were measured using impedance analyzer. Largest peak mi, MI and ACMR of 1615%, 61% and 69% were observed for the nanocrystalline x=1.0 ribbon, at 100 kHz, 10 MHz and 13 MHz respectively. Magnetic domain structure was studied in the ribbons through magnetic force microscopy.     

Fabrications and mechanical properties of bulk amorphous,nanocrystalline, nanoquasicrystalline alloys in aluminum-based system

By controlling the composition, clustered atomic configuration and stability of supercooled liquid by the rapid solidification and powder metallurgy techniques, high-strength Al-based bulk alloys containing nanoscale nonperiodic phases were produced in Al–Ln–LTM, Al–ETM–LTM and Al–(V, Cr, Mn)–LTM (Ln=lanthanide metal, LTM=VII and VIII group transition metals, ETM=IV–VI group transition metals) alloys containing high Al contents of 92–95 at.%. The nonperiodic phases are composed of an amorphous or an icosahedral quasicrystalline phase. In particular, the Al-based bulk alloys consisting of nanoscale icosahedral particles surrounded by fcc-Al phase exhibit much better mechanical properties exceeding largely those for the commercial high-strength type Al-based alloys. The success of producing the Al-based alloys with good engineering properties by use of the icosahedral phase is promising for future development of icosahedral base alloy as practical materials.     

Effect of thermal and thermochemical treatments on the structure of Fe-Ni submicrocrystalline electrodeposited multilayer materials

The effects of annealing, carburization, and quenching on the structural changes in a mulilayer Fe-Ni material fabricated by electrolytic deposition from aqueous electrolytes have been studied. The thermal stability of this structure is shown to be identical to that of the related materials produced by severe plastic deformation. When an interstitial element with different affinities to the base components is added to the composite material under study, the diffusion rate of its metallic atoms (including those that are not involved in the formation of interstitial phases) decreases. In the quenched composites, the morphological type of martensite in ironbased layers is determined by the content of alloying elements (carbon, nickel), as in the corresponding bulk materials.     

Sintering of iron—silicon—boron magnetically soft steels

An investigation of structure formation in multicomponent magnetically soft powder metallurgy steels was carried out. A model for the homogenization of Fe?Si-0.06% B alloys over a wide range of silicon concentrations is proposed. The optimal processing regime was determined. Highest magnetic induction was obtained in a 1% Si alloy, and highest permeability in a 6.5% Si alloy (both are sintered at 1300°C for 6 h).     

Mechanisms of hydrogen embrittlement and fracture of nanocrystalline materials

The physical mechanisms of hydrogen embrittlement and fracture of nanocrystalline materials due to the molecular hydrogen pressure in cavities and the formation of hydride phases are proposed and justified mathematically.     

On the problem of the maximum strength of metals and alloys in crystalline,amorphous, and nanocrystalline states

The true breaking stresses and the ultimate tensile strengths of 11 metals with various structures are calculated. Moreover, the fracture strengths of these metals at 0 and 298 K are calculated in the amorphous (σ _{f, a}) and nanocrystalline (σ _f,nano^max) states formed upon severe plastic deformation. The temperature dependences of these properties are also determined. These properties are obtained for a number of alloys (TiNi, NiNb, Pd₈₀Si₂₀, Ni₆₀Nb₄₀). The values of σ _{f, a} are shown to correlate with yield strength σ_{y, nano} of nanocrystalline substances, and a hypothesis of a deviation from the Hall-Petch relation is advanced. This hypothesis is supported by the calculation of the properties and diffusion characteristics. The obtained numerical results agree satisfactorily with the experimental data and the results of other approaches to estimating these properties.     

高饱和磁化强度铁基非晶纳米晶软磁合金发展概况

概括了铁基非晶软磁合金和纳米晶合金的发展历史和现状,分别详述了高饱和磁化强度(B_s)铁基块体和薄带非晶以及纳米晶合金近年来的研究成果.主要内容包括:高饱和磁化强度块体铁基非晶软磁合金成分和性能,高饱和磁化强度铁基非晶薄带软磁合金的成分和性能,高饱和磁化强度铁基纳米晶合金的组织、结构和性能,各类元素对合金磁性能的影响.为进一步研究高饱和磁化强度的铁基软磁材料提供了有价值的参考.     

等离子喷涂制备铁基非晶-纳米复合涂层

以一种多元素铁基非晶合金粉末(含C,Si,B,Cr,W,Mo,Ni,Fe等)作为喷涂材料,用大气等离子喷涂在316L不锈钢基体上制备涂层.用X射线衍射仪检测涂层的晶型结构,扫描电镜观察涂层的形貌,透射电镜观察涂层的微观组织结构,显微硬度仪测量涂层的显微硬度,纳米压痕仪测量涂层的硬度及弹性模量,并用谢乐公式计算了晶粒尺寸.结果表明:所制备的涂层均匀致密,与基体结合良好;涂层含有非晶和纳米颗粒;这种非晶-纳米复合涂层具有很高的硬度和弹性模量.