Processing of ultra fine size particulate metal matrix composites by advanced shear technology

Abstract

Lack of efficient mixing technology to achieve a uniform distribution of fine size reinforcement within the matrix and the high cost of producing components have hindered the widespread adaptation of particulate metal matrix composites (PMMCs) for engineering applications. A new rheo processing method, the melt conditioning high pressure diecasting (MC-HPDC) process, has been developed for manufacturing near net shape components of high integrity. The MCHPDC process adapts the well-established high shear dispersive mixing action of a twin-screw mechanism to the task of overcoming the cohesive force of the agglomerates under a high shear rate and high intensity of turbulence. This is followed by direct shaping of the slurry into near net shape components using an existing cold chamber diecasting process. The results indicate that the MC-HPDC samples have a uniform distribution of ultra fine sized SiC particles throughout the entire sample in the as-cast condition. Compared to those produced by conventional high pressure diecasting (HPDC), MC-HPDC samples have a much improved tensile strength and ductility.