Papers by Author: Kamanio Chattopadhyay

Abstract: The present study has been taken up to establish fracture property correlation of the semi solid processed 6061 aluminium alloy. Electro Magnetic Stirring (EMS) has been performed to get non-dendritic billets and then the alloy has been thixocast using a High pressure die casting machine. Tensile tests have been performed to estimate mechanical properties of the semi solid processed alloy. Fracture behaviour of the alloy has been investigated at the intermediate EMS cast state and subsequent final thixocast state, employing uniaxial tensile tests at 0.001s^-1 strain rate and at room temperature. Fracture surface morphology of the EMS cast state shows that the presence of micro porosity is responsible for crack initiation and final fracture. Our results confirm that the dimpled rupture of primary Al phase is responsible for improved mechanical properties in the thixocast state of the alloy.

Abstract: In this paper, a numerical model for friction welding of thixo-cast materials is developed, which includes a coupling of thermal effect and plastic deformation using a finite element method (FEM). As the constitutive equations for flow behavior of materials for a thixo-cast material are expected to be different from those of conventionally cast material of the same alloy, the necessary material data are experimentally determined from isothermal hot compression tests of the A356 thixocast alloy. The Johnson-Cook model has been employed to represent the flow behavior of the thixocast A356 alloy. The purpose of this FEM analysis is to provide better understanding of the friction welding process of thixo-cast material, and to obtain optimized process parameters before an actual welding is carried out.

Abstract: In the present work, a thorough investigation of evolution of microstructure and texture has been carried out to elucidate the evolution of texture and grain boundary character distribution (GBCD) during Equal Channel Angular Extrusion (ECAE) of some model two-phase materials, namely Cu-0.3Cr and Cu-40Zn. Texture of Cu-0.3Cr alloy is similar to that reported for pure copper. On the other hand, in Cu-40Zn alloy, texture evolution in α and β (B2) phases are interdependent. In Cu-0.3Cr alloy, there is a considerable decreases in volume fraction of low angle boundaries (LAGBs), only a slight increase in CSL boundaries, but increase in high angle grain boundaries (HAGBs) from 1 pass to 4 passes for both the routes. In the case of Cu-40Zn alloy, there is an appreciable increase in CSL volume fraction.