Microstructural analysis of fusion and heat affected zones in electron beam welded ALLVAC 718PLUS™ superalloy

The fusion zone and heat affected zone (HAZ) microstructures of electron beam welded superalloy 718PLUS™ (718 Plus) that has been newly developed by ATI ALLVAC were examined. The microsegregation pattern during solidification of the fusion zone indicated that while Fe, Co, W, and Cr segregated to the core of the gamma dendrites, Nb, Ti, and Al were extensively rejected into the interdendritic liquid. Electron diffraction and X-ray microanalysis using transmission electron microscopy (TEM) of the fusion zone showed that the major secondary phases that formed from the interdendritic liquid were gamma/MC type carbide eutectic and gamma/Laves eutectic constituents. HAZ microstructure showed partially melted zone immediately adjacent to the fusion zone and intergranular microfissuring associated with resolidified products which suggested that HAZ cracking in this alloy occurred by liquation cracking. Microstructural examination of the HAZ using analytical scanning electron microscope showed resolidified gamma/Laves eutectic on the cracked and backfilled grain boundaries. Fine resolidified MC type carbide particles were also observed in the HAZ. Causes of grain boundary liquation were identified and the solidification of intergranular liquid in the HAZ was discussed.     

Probabilistic query generation and fuzzy c‐means clustering for energy‐efficient operation in wireless sensor networks

Depending upon sensing attributes, wireless sensor networks (WSNs) are classified as event driven, time driven, and query driven. In a given surveillance area, approximation of query generation process using uniform probability mass function (PMF) model seems to be reasonable in aggregate terms based on observations extracted from lifetime span of WSNs. However, owing to random generation aspects of query and the associated temporal variations, the Poisson distribution‐based model appears to be more appropriate to resemble the realistic query generation pattern. Invariably, in all the sensor network architectures, the energy management requires an important consideration owing to limited energy resources. For the optimal utilization of energy resources, we propose fuzzy c‐means (FCM) algorithm to form clusters in a hierarchical network configuration. Network performance is measured in terms of key performance measures, namely, average residual energy status, critical residual energy status (CRES), and number of network nodes that attain the CRES mark. These performance measures are estimated and analyzed for three different PMF models of query generation namely Uniform, Gaussian and Poisson. The merit of deploying FCM algorithm in terms of maintaining much better energy profile of the entire network is discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermal treatment of toxic metals of industrial hazardous wastes with fly ash and clay

Waste generated from galvanizing and metal finishing processes is considered to be a hazardous due to the presence of toxic metals like Pb, Cu, Cr, Zn, etc. Thermal treatment of such types of wastes in the presence of clay and fly ash can immobilizes their toxic metals to a maximum level. After treatment solidified mass can be utilized in construction or disposed off through land fillings without susceptibility of re-mobilization of toxic metals. In the present investigation locally available clay and fly ash of particular thermal power plant were used as additives for thermal treatment of both of the wastes in their different proportions at 850, 900 and 950 degrees C. Observed results indicated that heating temperature to be a key factor in the immobilization of toxic metals of the waste. It was noticed that the leachability of metals of the waste reduces to a negligible level after heating at 950 degrees C. Thermally treated solidified specimen of 10% waste and remaining clay have shown comparatively a higher compressive strength than clay fired bricks used in building construction. Though, thermally heated specimens made of galvanizing waste have shown much better strength than specimen made of metal finishing waste. The lechability of toxic metals like Cr, Cu, Pb and Zn became far below from their regulatory threshold after heating at 950 degrees C. Addition of fly ash did not show any improvement either in engineering property or in leachability of metals from the solidified mass. X-ray diffraction (XRD) analysis of the solidified product confirmed the presence of mixed phases of oxides of metals.     

Fatigue crack growth behavior of X2095 Al–Li alloy

Microstructures and micro-textures of X2095 Al–Li alloy in as-received/superplastic state were characterized by means of SEM/BDS, X-ray diffraction and orientation imaging microscopy (OIM). It was observed that the microstructure of the alloy was typical of a particulate-reinforced composite material, consisting of aluminum matrix and homogeneously distributed T_B(Al₇Cu₄Li) particles with a volume fraction of about 10%. Brass-type texture was the dominant texture component. Both constant amplitude and near-threshold fatigue crack growth rates of the alloy in the L–T and T–L orientations were determined at different stress ratios. Particular attention was paid to the role of the T_B phase in the fatigue crack growth. When a fatigue crack approached a T_B particle, the crack basically meandered to avoid the particle. The T_B particles thus provided a strong resistance to the propagation of fatigue crack by promoting crack deflection and the related crack closure effects. The fatigue crack propagation behavior has been explained by the microstructural features, micro-textures, cracking characteristics and crack closure effects.     

Integrated Manufacturing System for Precision Press Tooling

The press tooling industry, characterised by many small-scale job-shops, is facing an increasingly competitive global market. This comes at a time when there is a shortage of experienced process planners and unavailability of affordable CAD/CAM systems that could provide an integrated solution for manufacturing sheet metal tooling. Many commercially available CAD/CAM systems are either too expensive or too narrow in scope, in the sense that they provide only point solutions. The design of press tools and its manufacturing functions are highly specialised and knowledge-intensive in nature. This paper presents a framework and the implementation details of an integrated system that has been developed for a local sheet metal tooling company specialising in precision punches and dies. A PC-based system has been implemented on an AutoCAD platform using the Autolisp programming language.     

Solution of the Master Equation for an Attenuated or Amplified Nonlinear Oscillator with an Arbitrary Initial Condition

Abstract

Using the thermo-field dynamics notation, an elegant solution of the master equation for an attenuated or amplified nonlinear oscillator is presented. It is found that, in this notation, the solution of the master equation under consideration amounts to a simple modification of that for the linear oscillator.     

Nanoferrites: Catalyst for Thermal Decomposition of Ammonium Per Chlorate

Nanoferrite nanoparticles were synthesized by chemical coprecipitation method. The ferrite nanoparticles such as Zn, Mn, Ni, Co, and Cu were prepared. All nanoparticles were characterized by x-ray diffraction and scanning electron microscopy. The average particle of Zn, Mn, Co, Ni and Cu ferrite are 6.8, 2.7, 5.2, 1.1 and 3.9 nm respectively. The effect of ferrite nanoparticles on the thermal decomposition of ammonium per chlorate was studied using thermogravimetic analysis, differential scanning calorimetric (DSC) studies. Activation energy of high temperature decomposition of different alloy nanoparticles was calculated using DSC by Kissinger equation. The catalytic activity of nanoferrites is much sensitive to oxygen and may be effective to improve the thermal decomposition AP-based propellants.     

Synthesis and Structure of Environmentally Friendly Hybrid Clay/Organosilane Nanocomposite Coatings

Environmentally friendly polysiloxane and clay/polysiloxane composite coatings were synthesized on aerospace-grade aluminum alloy AA2024-T3 substrates from mildly acidified aqueous solution. The polysiloxane coatings were synthesized by acid-catalyzed hydrolysis and condensation of organosilane coupling agents such as glycidoxypropyltrimethoxysilane (GPTMS) and tetramethoxysilane (TMOS) followed by solution drop-casting onto the substrate to form self assembled nanoparticles, coating. The epoxy polysiloxane coating formed by condensation reaction of hydrolyzed TMOS and GPTMS was subsequently cured with aminosilane coupling agent to form cross-linked polysiloxane coating. Clay/polysiloxane coating was formed by dispersing about 0.1–0.3wt% of clay in the hydrolyzed TMOS/GPTMS solution followed by solution casting and the resulting clay/polysiloxane composite coating was subsequently cured with aminosilane coupling agent. The structure and composition of organosilane coupling agents and hybrid polysiloxane coatings were determined by reflection–absorption infrared spectroscopy (RAIR) and X-ray diffraction spectrometry (XRD). The hydrolysis, condensation and curing reactions of TMOS and the organosilane coupling agents were studied by analyzing thin films cast on aluminum alloy substrate after a predetermined reaction time by using RAIR. The XRD results show that the resulting polysiloxanes are semi-crystalline polymers. Wide angle XRD analysis indicated that clay dispersed in clay/polysiloxane composite coating is either highly intercalated or partially exfoliated. This inference was drawn from the disappearance of d₀₀₁ diffraction peak for clay from the XRD spectrum of clay/polysiloxane coatings cured at 100 °C for 2.5 h.