Papers by Author: I. Manna

Abstract: The microstructure, phase composition, Mössbauer spectra, grain boundary segregation and magnetic properties of binary Fe–C alloys with carbon concentration of 0.05, 0.10, 0.20, 0.25, 0.45, 0.60, 1.3, 1.5 and 1.7 wt. % were studied in the as-cast state, after a long annealing at 725°C and after high-pressure torsion (HPT) at the ambient temperature and 5 GPa with 5 anvil rotations (shear strain about 6). The grain size after HPT was in the nanometer range. Only Fe3C (cementite) and -Fe remain in the alloys after HPT. It was also shown that the less stable Hägg carbide (Fe5C2) and retained austenite disappear, and phase composition closely approaches the equilibrium corresponding to the HPT temperature and pressure. Measurements of saturation magnetization and Mössbauer effect reveal that the amount of cementite decreases after HPT. The reason for partial cementite dissolution is the formation of the carbon-rich segregation layers in the ferrite grain boundaries.

Abstract: Mechanically alloyed Al65Cu20Ti15 amorphous alloy powder with 10 wt.% nano-TiO2 dispersion was consolidated by high pressure sintering (HPS) at room temperature and/or 300- 450oC for about 1 min using a uniaxial pressure of 8GPa. The sintered material was examined by XRD and TEM. Excellent hardness and strength were obtained in selected sintered samples of 8.34 GPa and 1600 MPa respectively, although ductility was very low (< 1%).

Abstract: The paper examines the phase evolution in blends consisting of different proportions of stainless steel (SS316) and Al (0, 25, 65 and 85 wt. %) powders during high-energy ball milling by x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy. An attempt has also been made to study the mechanical property of the bulk samples obtained by hot pressing the ball milled powder blend at suitable a temperature and pressure. The results of microstructural changes and mechanical property and the ability of consolidation of the amorphous/nanocrystalline powders by high-pressure techniques to develop engineering components has been discussed and highlighted.