Development of ultrafine grained high strength age hardenable Al 7075 alloy by cryorolling

High strength age hardenable Al 7XXX series alloys are difficult to process by many of the severe plastic deformation processes at room temperature. The Al 7075 alloy has been processed at cryogenic temperature and room temperature up to different rolling strains, in the present work, with the objective of developing a processing strategy to obtain ultrafine grained microstructure with enhanced mechanical properties in the alloy. It has been identified that the Al 7075 alloy samples can be successfully cryorolled to higher strains (up to 3.4) if the reduction per pass is less than 0.3 mm, however it was found to be difficult to deform the samples at room temperature. A cryorolling strain of 3.4 has been found to be desirable for producing the ultrafine grained Al 7075 alloys with the high angle grain boundaries. However, the subgrains are not recrystallized up to this strain in the case of room temperature rolled Al alloys. The strength and hardness of the cryorolled Al 7075 alloy samples are higher than that of the room temperature rolled samples as observed in the present work. The improved strength and hardness of cryorolled samples are due to the grain size effect and higher dislocation density. The reduction in dimple size of cryorolled Al 7075 alloy upon failure confirms the grain refinement and strain hardening mechanism operating in the heavily deformed samples.     

A Novel Cascaded PID Controller for Automatic Generation Control Analysis With Renewable Sources

Present day power scenarios demand a high quality uninterrupted power supply and needs environmental issues to be addressed. Both concerns can be dealt with by the introduction of the renewable sources to the existing power system. Thus, automatic generation control (AGC) with diverse renewable sources and a modified-cascaded controller are presented in the paper. Also, a new hybrid scheme of the improved teaching learning based optimization-differential evolution (hITLBO-DE) algorithm is applied for providing optimization of controller parameters. A study of the system with a technique such as TLBO applied to a proportional integral derivative (PID), integral double derivative (IDD) and PIDD is compared to hITLBO-DE tuned cascaded controller with dynamic load change.The suggested methodology has been extensively applied to a 2-area system with a diverse source power system with various operation time non-linearities such as dead-band of, generation rate constraint and reheat thermal units. The multi-area system with reheat thermal plants, hydel plants and a unit of a wind-diesel combination is tested with the cascaded controller scheme with a different controller setting for each area. The variation of the load is taken within 1% to 5% of the connected load and robustness analysis is shown by modifying essential factors simultaneously by ± 30%. Finally, the proposed scheme of controller and optimization technique is also tested with a 5-equal area thermal system with non-linearities. The simulation results demonstrate the superiority of the proposed controller and algorithm under a dynamically changing load.      

Application of remote sensing technology for groundwater potential evaluation

With the help of the information drawn from a survey of India toposheet and by visual interpretation of satellite imagery of bands 2, 3 and 4, different thematic maps such as geomorphology and lineaments, drainage and land use, and land cover were prepared. These thematic maps have been superimposed and finally a groundwater potential zone map delineated on a survey of India toposheet. The whole block has been demarcated into 5 zones. Zones 1 and 2 are considered ideal groundwater potential areas, zone 3 is moderately ideal, and zones 4 and 5 are unfavourable for groundwater exploration. The validity of demarcation of the study area into different zones, as decided by remote sensing technology, has been justified by analysing the georesistivity sounding data of a number of places in this area. The net potential of the study area is estimated by GEC norm. It is observed that only 11.8% of annual utilisable groundwater is now used and there is vast scope of further exploitation of this resource.     

Preparation of Al--Al2O3 in-situ particle composites by addition of Fe2O3 particles to pure Al melt

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Reservoir Operation Modelling with Fuzzy Logic

In this article, a fuzzy rule based model is developed for the operation of a single purpose reservoir. The model operates on an 'if – then' principle, where the 'if' is a vector of fuzzy premises and the 'then' is a vector of fuzzy consequences. The steps involved in the development of the model include, construction of membership functions for the inflow, storage, demand and the release, formulation of fuzzyrules, implication and defuzzification. The methodology is illustrated through the case study of the Malaprabha irrigation reservoir in Karnataka, India. Reservoir storage, inflow, and demands are used as premises and the release as the consequence.Simulated reservoir operation with a steady state policy provides the knowledge base necessary for the formulation of the Fuzzy rules.     

Study of deuterium metal interaction by ion implantation

Dynamic and non-equilibrium effects involving interaction between deuterium and radiation produced defects were studied during deuterium implantation of Cu and Ti. The technique of neutron yield measurement during deuterium implantation was employed and theoretical analysis was made to study the dynamics. SIMS, GIXRD and SEM studies on deuterium implanted samples were employed to study the evolution of implanted deuterium profiles, structure of deuterides and surface topography respectively.     

Effect of copper and nickel coating on short steel fiber reinforcement on microstructure and mechanical properties of aluminium matrix composites

Commercially pure Al base short steel fiber reinforced composites were prepared by stir casting method and poured into a cast iron mould. Steel fibers were coated with copper and nickel by electroless deposition method. The density, hardness and strength of composites increased as compared to matrix alloy. The mechanical properties of these composites were measured and the results were correlated with the microstructure observation. It was found that copper-coated short steel fiber reinforced composites show considerable improvement in strength with good ductility because copper form a good interface between Al matrix and short steel fiber. Nickel-coated steel fiber reinforced composites showed improvement in strength to a lower extent possibly because of formation of intermetallic compound at the interface. The improvement in strength with uncoated fibers and nickel-coated fibers is on the lower side because of formation of brittle intermetallic compounds like Fe₂Al₅ and FeAl₃. Fracture surface of tensile specimen was examined under SEM, which revealed a ductile fracture. Copper coating on steel fiber improved the strength properties while retaining a high level of ductility due to better interface bonding.