Amitava Basu Mallick

Challenges in manufacturing aluminium based metal matrix nanocomposites via stir casting route

The influence of material processing conditions for preparing aluminium based metal matrix nanocomposites through stir casting route is reviewed. The role of particle size with respect to Brownian motion, Stokes settling velocity and strengthening mechanism is assessed from theoretical understandings. Variation of microstructural features and mechanical properties of the nanocomposites are predicted from theoretical concepts and related mathematical models. Experiments conducted to validate the theoretical predictions show that both Orowan and grain refinement strengthening mechanisms remain operative which is the key to the improved strength property of the nanocomposites.

Microstructural, thermo-optical, mechanical and tribological behaviours of vacuum heat treated ultra thin SS304 foils

The purpose of this present study was to evaluate the effect of vacuum (i.e., 10−5 mbar) heat treatment at 300 to 1100 °C on morphological, thermo-optical, mechanical and tribological properties of 75 μm thin SS304 foils. Microstructural, morphological and surface properties of the foils were characterized by field emission scanning electron microscopy (FESEM), profilometry, x-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) measurement techniques, respectively. The x-ray diffraction (XRD) was employed to identify the phase of SS304 foils after different heat treatment temperatures. Thermo-optical properties such as solar absorptance (α s), reflectance (ρ s) and IR emittance (e ir) were also evaluated. The nanomechanical properties i.e., nanohardness (H) and Youngs modulus (E) of as-received and heat treated SS304 foils were evaluated by the nanoindentation technique. Tribological and tensile properties i.e., yield strength (σ y) and percentage of elongation of different heat treated foils were also investigated by single pass scratch tests and universal testing machine, respectively. Noteworthy grain growth of SS304 was observed beyond vacuum heat treatment temperature of 700 °C. As a consequence, the magnitudes of both H and E data of SS304 were significantly decreased beyond the vacuum heat treatment temperature of 700 °C. Further, the hardness data followed the well known Hall–Petch relationship. On the other hand, the tribological property of SS304 was significantly deteriorated beyond the vacuum heat treatment temperature of 700 °C. The tensile strength of the foils was also altered after the heat treatment.

Pitting Enhanced Fatigue in 7075 Aluminium Alloy

Pitting corrosion of two tempers (T6 and T73) of 7075 Aluminium alloy were quantified by digital image processing. The effect of pitting corrosion on fatigue life in 7075 Aluminium alloy in two aging conditions was studied. Pitting was found to be slightly more severe for T6 tempers compared to T73 tempers for different time of exposures. The fatigue lives of two tempers of 7075 Aluminium alloy at high peak stresses were compared in the uncorroded and pre-corroded (pitted) states. Absolute fatigue lives of T73 samples were much higher than that of T6 in the uncorroded as well as pre-corroded condition. The various crack initiation methodologies observed through fractographic analysis is discussed.

Preparation of FeCo/Cu Core Shell Magnetic Nanoparticles

FeCo/Cu core shell structure with FeCo as a core and copper as the shell has been successfully synthesized by displacement reaction. The morphology, grain size, lattice strain, and magnetic properties of all the samples were examined by using transmission electron microscopy (TEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). Annealing temperatures and its effect on magnetic properties of the FeCo/Cu core shell particles was investigated. A maximum coercivity (Hc) of 398.84 Oe was recorded for the sample heat treated in magnetic field. The blocking temperatures (TB) and squareness (Mr/Ms) of the sample gradually increased due to the influence of temperature and magnetic field.

Magnetic Behaviour of FeCo/Cu Core Shell Nanoparticles

In the present investigation, FeCo/Cu core shell nanoparticles were prepared by coating a Cu layer over FeCo alloy nanoparticles through displacement reaction. X-ray diffraction studies confirmed the presence of FeCo and Cu phases in the sample. The grain size and lattice strains of the core shell nanostructures were evaluated from the x-ray profiles by using single line profile analysis technique. The effect of annealing temperature on the magnetic properties of the core shell nanoparticles was studied by using a vibrating sample magnetometer. The results showed that the magnetic properties improve significantly after annealing the compacts of core shell nanoparticles under a magnetic field. Enhancement in magnetization was observed in the compacts with the increase in annealing temperature. Highest saturation magnetization value of 56 emu/g was recorded in the sample which was annealed at 600°C. It has been also found that the blocking temperature of the core shell nanoparticles increases with the increase in annealing temperature.

Crystallization Behavior and Curie Temperature Properties of Al Doped Nd-Fe-B Based Nanocomposite Permanent Magnet

The work is primarily concerned with the development of nanocrystalline Nd-Fe-B, based permanent magnet with high Curie temperature. An alloy of composition Fe81Nd7Al2B10 has been prepared using vacuum arc furnace and subjected to using Melt-Spinning process for preparation of amorphous flakes. Differential scanning calorimetry (DSC) has been performed to determine the crystallization temperature and activation energy of the melt spun amorphous ribbons. Subsequently the melt spun ribbon was subjected to annealing at below and above the crystallization temperatures to identify effect of Al on the Curie temperature. It was noteworthy for the effect of alloying Al above crystallization temperature. The Curie temperature increases to by almost 1.3 times with increase in annealing temperature.