Papers by Keyword: Solute Concentration

Abstract: In a previous study, the damping capacity gradually increased with increasing annealing time and temperature in AZ31. Also, at damping capacity test under similar conditions, AZ61 with a higher solute content showed a more rapid microstructure change than AZ31. In this study, it was investigated damping capacity on various aluminum concentration conditions in order to damping capacity that was influenced by microstructure and solute content. Three types such as pure Mg, AZ31 and AZ61 alloy of specimens were rolled at 673K with a rolling reduction of 30%, respectively. The annealing were conducted at various temperature and time. In this study, static recrystallization was occurred under all annealing conditions. The hardness gradually decreased until 60 minutes after the heat treatment. All annealing conditions, the damping capacity gradually increased with increasing annealing time and temperature. Especially, damping capacity and C₁ value were increased with a decreasing of solute content.

Abstract: Temperature Gradient Zone Melting (TGZM) occurs when a liquidsolid zone is submitted to a temperature gradient and leads to the migration of liquid droplets or channels through the solid, up the temperature gradient. TGZM has a major influence on the preparation of the initial solid-liquid interface during the stabilization phase following the directional melting of an alloy and is at the origin of the diffusion of solute towards the top part of the mushy zone. TGZM is also causing the migration up the temperature gradient of dendrite secondary arms during directional solidification, which can have a significant impact on the micro-segregation pattern of the final microstructure. In this communication we report on a directional solidification experiment carried out at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France) on Al4.0 wt.% Cu alloy to study the dynamics induced by the TGZM phenomenon on an equiaxed grain that nucleated in front of a columnar structure. Based on in situ experimental observations obtained by synchrotron X-ray radiography, the dissolution of the bottom part of the equiaxed grain is characterized and measurements are compared with predictions of the TGZM theory in diffusive regime.

Abstract: To investigate the effect of high magnetic fields on the solidification behavior of binary eutectic system, solidification and quenching experiments of Al-11.8 wt.%Si and Ag-10 wt.%Cu alloys were carried out with and without an 8.8 T high magnetic field. It was found that the application of the high magnetic field could increase the concentration of Si in the primary Al and Cu in the primary Ag at their eutectic temperatures, but could not obviously affect the Si concentration in the primary Al at room temperature. The above increase can be attributed to the weakness of the solute diffusion at the liquid-solid interface during solidification caused by the high magnetic field.

Abstract: The influences of solution treatments, prior cold drawings and aging treatments on mechanical properties in Corson alloy with high contents more than 8.0 mass% of Ni and Si have been investigated. As a result of the optimization of conditions, the maximum hardness and tensile strength reached 306HV and 968MPa, respectively. Effects of temperatures of solution treatment and aging on the mechanical properties were analyzed based on solid solute concentrations in matrix phase, which were estimated by using the linear analysis and calculated from the electrical conductivity. The solute concentrations were also measured directly by SEM-EDS. Consequently, the precipitation hardening of the alloys was governed mainly by the solute concentrations of Ni and Si in matrix phase in solution treatment. The hardness depended on not only the solute concentrations but also the excess of Ni and Si in the alloys.

Abstract: A possibility of a modification of the Jackson-Hunt theory of an oriented structure formation is analysed. A new model for the formation of a concentration field ahead of growing regular lamellae with respect to the solid / liquid interface shape is presented. A coordinate system applied in the model is attached to the solid / liquid interface to be advancing in the z - direction, identically with interface moving at a constant velocity, v . The solution to a diffusion equation is given for the improved formulation of the boundary conditions. The boundary conditions are related to the interplay between the diffusion required for phase separation and the formation of the interphase between both lamellae. The boundary conditions are formulated to establish the stability of lamellar structure formation under steady-state conditions. It is assumed that stable growth of the lamellae is ensured by the separation of concentration fields within a boundary layer ahead of the solid / liquid interfaces of both the α and β " phases. Coupled lamellar growth with the presence of a leading phase protrusion is defined. The general mass balance is analysed for a solute concentration in the liquid, taking into account a planar solid / liquid interface. A local mass balance is also ensured but it requires envisaging a protrusion of the minor eutectic phase. The existence of a lead distance is confirmed experimentally for the (Pb)-(Cd) eutectic system. The difference in undercooling is also considered as a phenomenon associated with the separation of concentration fields and the existence of a protrusion to relax the assumption of an isothermal interface (ideally coupled growth) given by the Hunt and Jackson theory.