Pampa Ghosh

Effect of Ag nanoparticle addition and ultrasonic treatment on a stable TiO2 nanofluid

Nanoparticles, when homogeneously dispersed in a base fluid, e.g. water, ethylene glycol etc. are commonly known as nanofluids. Nanofluids have gained attention in the scientific community for their enhanced thermal properties. One of the major problems in using nanofluids as a heat transfer medium for commercial applications is that, in most of the closed circuit industrial cooling processes, the cooling fluid has to be replaced after several cycles of cooling operation because of an increased presence of contaminants. If nanofluids were used as a coolant, it would be very hard to separate the nanoparticles from the waste fluid. The present work is aimed at the separation and recycling of nanoparticles from fluid waste by means of quick settling of titanium dioxide nanoparticles using silver nanoparticles along with ultrasonic treatment. It is observed that with increasing silver concentration and time of ultrasonication, the stability of the dispersion decreases. There is a value for both the silver concentration and ultrasonication time above which the settling time decreases drastically.

Precipitation and Texture Formation in Interstitial Free High Strength (IFHS) Steels: A Short Review

Interstitial free high strength steels (IFHS) are widely used in the automobile sector due to their high strength and excellent formability. However, these properties of IFHS steels are very much dependent on the processing parameters, like hot rolling, cold rolling and annealing. The composition and processing parameters influence the chemistry and morphology of the precipitates formed in these steels, which in turn control the texture and thus the deep-drawability. This review will briefly summarize the findings of the ongoing research in this area. An attempt will also be made to elucidate the correlation of precipitation behavior and texture formation (and thus formability) in these steels.

Microstructure, texture, grain boundary characteristics and mechanical properties of a cold rolled and annealed ferrite–bainite dual phase steel

Abstract The microstructural, textural evolution and changes in grain boundary character distribution during annealing of a prior cold worked (30 %, 50 % and 80 %) ferrite–bainite dual phase steel have been studied and correlated with mechanical properties. It has been shown that submicron sized subgrains can be obtained by selecting the appropriate amount of cold rolling and annealing cycle. Increasing the annealing temperature in all the materials produces the expected results, namely decrease in strength with a simultaneous increase in ductility. Although reasonably sharp γ-fibres were obtained in 80 % cold rolled and its 500 °C annealed counterpart, the very low values (< 1.0) make the steel unsuitable for the purpose of deep drawing. It is envisaged that grain boundary engineering may lead to better strength–ductility combinations in this steel for an enhanced range of applications.

Effects of Deformation Texture and Microstructure on Recrystallization and Grain Growth in Twip Steels

The importance of TWinning Induced Plasticity (TWIP) and TRansformation Induced Plasticity (TRIP) has increased drastically in the recent past due their potential for automobile applications. These steels have good combination of specific strength and ductility, which could improve the crash resistance or energy absorption capacity in the situations like accidents. Stacking Fault Energy (SFE) is the most important parameter for the design of such steels. In low SFE TWIP steels, Brass (Bs)-type texture typically develops during rolling. Present investigation deals with the role of deformation texture, microstructure and SFE in recrystallization kinetics and grain growth, during processing in medium Mn steels. The SFE of Fe-12Mn-0.5C (wt %) alloy could be altered by the addition of alloying elements, such as Al. Recrystallization experiments have been carried out in cold rolled samples for different annealing times. In order to understand the recrystallization kinetics and grain growth phenomenon, detailed microstructural characterization has been performed by using Electron back-scatter diffraction (EBSD).

Precipitation Behavior and Textural Evolution in Interstitial Free High Strength (IFHS) Steels

Cold rolled and annealed interstitial free high strength (IFHS) steels show various kinds of precipitates. Out of these, FeTiP is the most deleterious, since its formation leads to a loss of strength as well as degradation of the formability of the steel. This effect is much more pronounced in batch annealed IFHS steels than in their continuous annealed counterparts. The harmful effects of FeTiP precipitation in batch annealed steels can be largely avoided by the use of appropriate coiling and annealing temperature, depending on the composition of the steel.