Effect of high energy ball milling on compressibility of nanostructured composite powder

Compressibility of a nanostructured Al-5AlN composite powder synthesised via high energy ball milling for various times was studied by means of a modified Heckel equation. Since workhardening and morphological changes take place by milling evolution, the compressibility was consequently affected. Strengthening of composite compacts was influenced by milling and compaction processes, i.e. strength of compacts increased at longer milling times and higher compaction pressures. It was found that, at the initial stages of milling and higher compaction pressures, the strengthening was mostly affected from compaction process, whereas the milling strengthening fraction was near to unity at lower compaction pressures as well as prolonged milling. Nevertheless, a sharp increase in milling strengthening fraction of unreinforced Al occurred at intermediate milling times. The rate of strengthening induced by milling raised at higher compaction pressures.