Papers by Author: B. Heidarian

Abstract: Continual improvement of product quality has been a long challenge to Semi-Solid Metal (SSM) technology. By conventional semi-solid processes, this might be attained at the expense of economical production. The advent of Inclined Cooling Plate (ICP) process has already realized the development of non-dendritic SSM while satisfying qualitative, quantitative and economical requirements collectively. In spite of its potential advantages, functional mechanisms of this process are not yet clearly understood that makes its optimal utilization obscured. Basically, such understanding needs a picture of the process. As the first step, this picture is pursued through physical modeling of the ICP process i.e. direct observation of an analog system by virtue of transparent character of a model alloy (succinonitrile-acetone). Based on this phenomenological model, a picture of the process is presented as follows: flowing molten alloy down ICP, multiple regions form typically on the plate i.e. a chilled layer at the vicinity of the plate surface, a two-phase mushy zone on the chilled layer and ambient liquid far from the plate surface. In this process, interaction of the liquid forced-flow with mushy zone separates solid particles from the stationary mush on the plate resulting in a two-phase mixture which is responsible for the formation of slurry i.e. SSM.

Abstract: Semi- solid (SS) processing technologies provide the production of metal parts with homogeneous, fine and globular – grained microstructure. This is one of the most successful and reliable methods to produce near net shape products exhibiting good mechanical properties. Production of feed stock with non-dendritic and spherical structure is the critical factors in semisolid forming. Among several processes to obtain a globular microstructure, the SIMA (strain induced melt activated) process is simple and advantageous with respect to equipment and eliminating the melting stage before reheating. In this research, Al (A356) has been used and in order to induce strain, ECAP (equal channel angular pressing) method has been applied. ECAP is a method in which a great strain is induced and severe plastic deformation without any changes in cross section area occurs. To induce larger strain, ECAP process was carried out on annealed specimens up to several passes in route A (no rotation of samples around linear axis between each pass) and Bc (90◦ rotation of samples around linear axis between each pass), in ambient temperature. The reheating condition was optimized and the comparison between different routes and number of passes was investigated. The microstructure evolution of deformed and reheated Al (A356) was characterized by SEM (Scanning electron microscopy) and optical microscopy. In addition, the relation between the induced strain with size and shape of particles has been studied.