Abstract
Particle reinforced aluminium alloy metal matrix composites (MMC) have proven to be one of the advanced materials capable of replacing conventional structural alloys. However, the demand for such materials has been confined to high cost applications due to their complex processing. A preliminary mechanical alloying (MA) of metal powder with ce-ramic particulates by High Energy Ball Mill (HEBM) processing is a step of MMC manufacturing process. In this paper mechanical alloying of aluminium alloys A356 and 7075 powder with Al2O3 and SiC par-ticulates using two types of HEBM was investigated. The effect of dispersed phase strengthening mechanism on three aluminium grade alloys was evaluated by micro hardness measurement. Microstructure investigation confirms the achieved strengthening results. It was established that by measuring hardness of alloyed aluminium particles with low load reliable information on the alloying effect can be achieved.
Highlights
The process of mechanical alloying (MA) can be used to produce alloys that are difficult or impossible to be produced by conventional melting and casting techniques
A preliminary mechanical alloying (MA) of metal powder with ceramic particulates by High Energy Ball Mill (HEBM) processing is a step of metal matrix composites (MMC) manufacturing process
MA is a process of repeated fracturing and cold welding of a metal powder mixed with ceramic particulates in a high energy ball mill, HEBM
Summary
The process of mechanical alloying (MA) can be used to produce alloys that are difficult or impossible to be produced by conventional melting and casting techniques. The main aim of this work is to investigate the strengthening effect of mechanical alloying on two aluminium alloys with nano and micro size ceramic particles, via microhardness measurements on the new metal matrix composites. It has been reported that the MA powders Oxide Dispersion Strengthened Superalloys recrystallise at exceptionally high homologous temperatures, around 0.9 of the absolute melting temperature (TM). This contrasts with 0.5 0.6 TM in ordinary metal forming processes of similar metallic alloys. The mechanically alloyed metals contain more stored energy than conventionally cold processed metals which recrystallise at lower temperatures [11]. The metal matrix powders used in this study are of cast A356 and wrought 7075 aluminium alloy compositions
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