Semi-Solid High Pressure Die Casting of Metal Matrix Composites Produced by Liquid State Processing

Abstract

There are two main technologies for manufacturing of particulate reinforced metal matrix composites (MMC), solid state and liquid state processing. The great challenge of producing cast metal matrix composites is to prevent agglomeration of particulates. This tendency is more pronounced with decreasing the particulate size to fine micro- and nano size. A method for producing MMC was successfully implemented for mixing hybrid, nano and low micron sized, reinforcing particles in an aluminium alloy matrix. The hybrid SiC particles were produced by milling 3µm to 5µm SiC particles to a particle size range between 2.5µm and 150 nm. The hybrid particles were mixed with A356 aluminium alloy under combined magneto-hydrodynamic (MHD) and mechanical stirring. The composite was then transferred to a High Pressure Die Casting (HPDC) machine in the semi-solid state. The micron size particles were found to be predominantly in the intergranular eutectic while the nano-particles were predominantly in the primary α-Al grains. Increased ultimate tensile strength, yield strength and hardness were achieved for the new cast metal matrix hybrid component (MMHC) alloy.

Wear Behaviour of A356 Aluminium Alloy Reinforced with Micron and Nano Size SiC Particles

“…Hybrid particulate SiC was achieved by milling micron (3-5 µm) size SiC powder. The procedure for milling and compocasting is detailed in the study preceding the current one [7]. Castings with 15 vol.% milled hybrid SiC particulate in A356 were produced.…”

“…Hybrid powders are useful and they have been employed in reinforcing metals as the nano particles improve the strength of the composite while the micron particles enhance the wear resistance of the composite [7][8][9][10]. Components reinforced in this way can thus be useful in applications where superior wear properties are required.…”

Metal Matrix Micro- and Nanostructural Composites (Review)

“…Therefore, the processes of solid-liquid shaping (thixoforming) are most promising for MMNCs and MMCs products [17][18][19][20].…”

Liquid Phase Production Technologies of Metal Matrix Composites (Review)

“…Biplanar MHD mixing of the wide-interval alloys, in particular, hypoeutectic silumins, in the liquid and two-phase states allows of solving the problem of equal distribution of the particles in the melt volume, ensuring the degeneration of the dendrite structure and the possibility to use all the advantages of thixocasting for producing nanocomposites [11][12][13][14].…”