An investigation of atomic short range order in palladium alloys by diffraction methods

An investigation of the degree of atomic short range order (ASRO) in alloys of palladium with scandium, dysprosium, titanium and manganese has been made using X-ray and neutron diffraction. The feasibility of performing such experiments is first discussed and following this, a number of alloys with different compositions and heat treatments have been examined. Measurable ASRO has been observed only in the most favourable cases Pd_0.86Ti_0.14 and Pd_0.85Mn_0.l5. The ASRO parameters have been determined for these examples and the form of the ASRO observed discussed in relation to long-range ordered phases.[/p]     

A novel route for preparing binary Sm–Co bulk amorphous alloys

A novel route for preparing binary amorphous alloy was proposed using Sm–Co system as an example. The alloy ingots with given compositions were used as the parent material. The amorphous intermetallic powder obtained by ball milling the parent alloy was consolidated by the high-pressure spark plasma sintering. The bulk amorphous alloy was detected and confirmed by X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The present route is potentially applicable to prepare a variety of binary and multicomponent bulk amorphous alloys with adjustable compositions.     

FEMMINA real-time, radio-frequency echo-signal equipment for testing novel investigation methods

Fast echographic multiparameter multi-image novel apparatus (FEMMINA), is a hardware and software platform dedicated to ultrasonic signal and image processing. FEMMINA is able to operate with sequences of radiofrequency (RF) frames. Its architecture is designed to be modular, expandable, and aimed at implementing different ultrasonic investigation techniques. The first experimental characteristic of this system is in its capability to operate in real time with ultrasonic RF signals, starting from acquisition up to processing, storage, and visualization. The second characteristic is the user-system interactivity that allows one to modify the operation appropriately while observing results. Currently, FEMMINA works in both typical experimental situations to study novel investigation techniques and clinical field to validate the proposed methods in different human districts.     

An investigation of segregation and mixing in dense phase pneumatic conveying

Pneumatic conveying of bulk materials has become an important technology in many industries: from pharmaceuticals to petro-chemicals and power generation. Particulate segregation has been investigated in many solids handling processes. However, little work has been published on the segregation and mixing in pneumatic conveying pipelines, particularly in dense phase pneumatic conveying. Due to the character of dense phase flow, it is difficult to investigate the segregation in a flowing plug. A sampling device was designed and built to take samples from the pneumatic conveying pipeline after “catching a plug”. Several experiments were conducted over a range of gas–solids flow conditions with 3 mm nylon pellets and 3 mm ballotini as a segregating mixture. Experimental data combined with video footage were analysed to describe the segregation and mixing of solids plugs in pipes. This investigation provides initial research on establishing a segregation index in a flowing plug. A gas–solids two-dimensional mathematical model was developed for plug flow of a nylon-glass particulate mixture in a horizontal pipeline in dense phase pneumatic conveying. The model was developed based on the discrete element method (DEM). The model was used to simulate the motion of particles both in a homogeneous flow and as binary mixtures taking into account the various interactions between gas, particles and pipe wall. For the gas phase, the Navier Stokes equations were integrated by the semi-implicit method for pressure-linked equations (SIMPLE) using the scheme of Patankar employing the staggered grid system. For the particle motion the Newtonian equations of motion of individual particles were integrated, where repulsive and damping forces for particle collision, the gravity force, and the drag force were taken into account. For particle contact, a model with a simple non-linear spring and dash pot model for both normal and tangential components was used. This model employed a mixture of 3 mm pellets and ballotini as virtual materials with properties of nylon and glass. The results from the model are discussed and compared with experimental work and show qualitative agreement. Further modelling and experimental work in key areas is proposed.     

Theoretical estimation of the effect of interfacial energy on the mechanical strength of spinodally decomposed alloys

New interfaces are produced on the slip plane when a crystal with continuous composition fluctuation arising from spinodal decomposition is deformed by slip. In this work, the energy of such interfaces is evaluated for both modulated and mottled structures, and their effects on slip behaviour are discussed. It is concluded that the contribution of this interfacial energy is large enough to account for the age-hardening concomitant with spinodal decomposition.     

An investigation of structural transformation during the solidification of copper-gallium alloys

Metallographic examination, X-ray diffraction, X-ray spectral microanalysis, and mlcrohardness measurements were used to study structural changes during the solidification of copper-gallium alloys. It was shown that the solidification of these alloys in the temperature interval 40–200°C takes place as a result of the formation of the -phase. Long-term holding at 200 and 300°C leads to the formation of ₃-, ₂-, ₁-, and-phases.     

制取铸造Al-Si合金EBSD样品的方法

铸造Al-Si合金的组织特殊,制取EBSD样品时难度较大.本文综述了目前常用的制取铸造Al-Si合金EBSD样品的方法,包括电解抛光、离子铣削和震动抛光,对不同方法在实验周期、可操作性、成本及样品表面质量等几方面的表现进行了对比分析.并以ZL114A合金作为实际操作合金,利用上述方法制备样品,进行EBSD分析,实验结果...     

An investigation of the unstable region for dense phase conveying in sliding bed flow

For fine powdered materials, capable of being conveyed in dense phase, a conveying region exists in which instability in flow and pipeline blockage can occur if the pressure gradient available is insufficient to maintain a minimum value of solids loading ratio. A reduction in material flow rate can also lead to pipeline blockage in this region. Conveying trials under-taken with cement are used to illustrate the nature of the problem.     

An experimental investigation of the structure of some internally oxidised ferromagnetic alloys

Results are presented of optical, scanning electron and transmission electron microscope observations on some internally oxidised ferromagnetic alloys. The alloys investigated were of nominal composition 0.058 wt % Si in Ni, 0.48 wt % Si in Ni and 0.17 wt % Si in Co 66.2%-Ni 33.7%. The alloys were in polycrystalline form and in addition single crystals of 0.058 wt % Si in Ni were examined. The diffusion and oxidation rate constants are calculated and the state of the oxide product as a function of (i) depth in the alloy, (ii) oxidising temperature and (iii) alloy composition is considered. The possibility of using such systems as device material and as test material for theories of coercivity and approach to magnetic saturation is considered.     

An experimental investigation of rate-dependent deformation and failure of three titanium alloys

The response of three titanium alloys, Ti 6,4, Ti 550 and Ti 6,2,4,6, commonly used in aerospace applications, has been investigated at rates of strain between 10⁻⁴ and 10³ s⁻¹ in uniaxial tensile and compressive loading in ambient environment. This work identifies and discusses features of their behaviour that must be captured within material models developed for use in predictive modelling of response to in-service loading. That is, an increase in yield strength with increasing strain rate, a difference in yield strength between tensile and compressive loading regimes and, most importantly, the evolution of damage resulting in failure due to growth of voids in both tension and compression.     

纳米材料的性质及其制备方法

回顾了近年来国内纳米材料研究的进展情况 ,详细介绍了纳米材料的基本性质、制备方法及其特点 ,并预测了其具有很大潜力的应用领域。     

An investigation of shape memory alloys as actuating elements in aerospace morphing applications

Two innovative actuating concepts for aerospace morphing applications, based on shape memory alloys (SMAs), are proposed. The first concept investigates a composite plate incorporating embedded SMA wires. A nonlinear auto regressive with exogenous excitation model is proposed for controlling single-cycle/multi-cycle loading conditions of the SMA wires. The second actuating concept studies a novel rib configuration, which incorporates a compliant mechanism for enabling aerofoil's leading edge morphing. Different rib-compliant mechanism concepts are designed and analyzed. The most efficient rib concept is experimentally characterized. The experimental results from both actuating concepts showed good agreement with the respective numerical.     

Structural investigation of amorphous iron-nickel-boron alloys

Accurate X-ray diffraction investigation has been made of ten amorphous alloys having the compositions (Fe_0.6Ni_0.4)_100–x B _x with x=14 to 24 and (Fe_100–y Ni _y )₈₀B₂₀ with y=30 to 70 which were obtained by rapid quenching from the melt. Using the common Fourier analysis, the radial distribution function was calculated from which the distance and its number of the near neighbour atoms were derived. The present results indicate that the atomic distribution of metallic glasses with low boron content differs slightly from that observed previously for a number of metallic glasses of transition metalmetalloid type. The compositional effect, in particular the boron concentration effect, on the structure and characteristic structural features of amorphous Fe-Ni-B alloy glasses is discussed together with the mean atomic volume and the partial atomic volume of metalloid elements using the measured density data.     

压力及制备条件对大块非晶合金结构的影响

大块非晶合金又称大块金属玻璃,是一种具有特殊结构与性能的新型金属材料.本文利用同步辐射XRD技术研究了常压和11.6GPa压力下Zr41.2Ti13.8Cu12.5Ni10Be22.5大块非晶合金结构以及0～50GPa压力范围内Fe60Co10Zr8Mo5Nb2B15大块非晶形成合金结构特征的演变.另外,利用同步辐射XRD研究了冲击波处理和水淬条件下制备的Zr41.2Ti13.8Cu12.5Ni10Be22.5大块非晶合金微观原子构型的差异.研究表明,压力与制备条件对大块非晶合金的结构均有一定影响,本研究对深入了解大块非晶合金结构本质及进一步开发该类材料具有重要理论和现实意义.     

Theoretical investigation of selective dissolution of alloys

We construct a quantum-chemical cluster model of interaction of α-brass and zinc-aluminum and ironchromium alloys with components of an acid aqueous solution of sodium chloride. We established the priority of an increase in the concentration of ions of zinc and iron as compared with the concentration of ions of other metals. The results of computation show that elastic mechanical deformations activate the process of selective dissolution of the alloys considered, which qualitatively agress with the experimental data. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 6, pp. 67–71, November–December, 1999.     

橡胶隔振器动态特性计算方法的研究

填充橡胶材料的动态特性与预载、激振频率和激振振幅等相关.采用模型叠加方法,建立了用于计算的由填充橡胶材料制造的橡胶隔振器动态特性的弹性-粘弹性-弹塑性模型.其中,弹性模型用于表征橡胶隔振器的弹性部分,粘弹性模型用于表征橡胶隔振器动态特性与激振频率的相关性,弹塑性模型用于表征橡胶隔振器动态特性与激振振幅的相关性.对一试片进行静动态性能实验,得到其静、动刚度和滞后角,由其拟合得到了弹性、粘弹性、弹塑性模型的参数.计算了一动力总成橡胶隔振器的动态特性,并与实验结果进行了对比分析.结果表明.采用的弹性一粘弹性一弹塑性模型可以较好地表征橡胶隔振器动态特性的振幅相关性和频率相关性.其计算方法,可以用于橡胶隔振器动态特性的设计计算.