Processing of Ultrafine-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 die-cast (MC-HPDC) process, has been developed for manufacturing near-net-shape components of high integrity. The MC-HPDC 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 die-casting process. The results indicate that the MC-HPDC samples have a uniform distribution of ultrafine-sized SiC particles throughout the entire sample in the as-cast condition. Compared to those produced by conventional high-pressure die casting (HPDC), MC-HPDC samples have a much improved tensile strength and ductility.

Microstructural Evolution and Property Evaluation of In Situ Al–MgAl2O4 Nanocomposite Prepared by γ‐Al2O3 and Ultrasonication‐Assisted Impeller Mixing

“…[ 7,8,20 ] In the ultrasonication‐assisted impeller mixing technique, the impeller mixing ensures the distributive mixing of the γ‐Al 2 O 3 particle agglomerates (i.e., the distribution of agglomerates within the liquid) and the ultrasonication leads to the dispersive mixing (i.e., the dispersion of agglomerates into individual particles and their distribution in the liquid). [ 21 ] It was shown before that the cohesive energy required to break the agglomerates is higher than the applied shear stress by the impeller and hence the agglomerates remain intact in the Al melt. [ 22 ] These agglomerations can be effectively dispersed by the ultrasonic treatment to ensure uniform distribution of MgAl 2 O 4 particles in the metal.…”

Effect of intensive shearing on morphology of primary silicon and properties of hypereutectic Al–Si alloy

“…During the dispersive mixing process, there is an enormous amount of ever changing interfacial area between the melt, the screws and the barrel. It has been reported 29,30 that intensive shearing helps to break up the agglomerates of solid particles and disperse them uniformly throughout the entire volume of the melt. Similarly, the intensive mixing action and melt conditioning are likely to disperse the Si clusters and fragment any potential nucleation agents, 26,31 and hence increase their potency for heterogeneous nucleation.…”

A Contemporary Review of Aluminium MMC Developed through Stir-Casting Route

“…At 600 rpm with 10 min stirring resulted in uniform hardness. Barekar et al obtained regular stir casting results of particles agglomeration that induces very low ductility in composites [28]. Palanikumar and Karthikeyan as well as lKylyckap et al optimized the parameter such as the feed rate, the SiC% volume fraction, and the cutting speed to obtain the minimum surface roughness [29,30].…”