Bulk amorphous and nanocrystalline Al83Fe17 alloys prepared by consolidation of mechanically alloyed amorphous powder

In the present work, bulk amorphous and nanocrystalline Al83Fe17 alloys were obtained by consolidation of mechanically alloyed powders. Mechanical alloying of Al-17% Fe powder mixture yielded powder with an amorphous structure. Thermal behaviour of the milling product was examined using differential scanning calorimetry. This investigation revealed that the amorphous phase crystallised above 380 °C. The amorphous powder was compacted under a pressure of 7.7 GPa in different conditions: at 380 °C for 600 s and at 1000 °C for 180 s. Structural investigations of the bulk material revealed that the amorphous structure was retained after consolidation process applied at 380 °C. Compaction under high pressure at 1000 °C caused crystallisation of the amorphous phase and appearance of metastable nanocrystalline phases, different to those which crystallised during heating in the calorimeter under atmospheric pressure. The microhardness of the bulk amorphous sample is 760 HV0.2, whereas that of bulk nanocrystalline one is 630 HV0.2. The density of the bulk amorphous material is 3.505 g/cm3 and is ∼3% lower than that of the nanocrystalline one. The open porosity of both consolidated materials is 0.4%. The results obtained show that the quality of compaction preserving amorphous structure as well as of the one yielding nanocrystalline structure is satisfactory and the products' microhardness is relatively high. The results also indicate that application of high pressure affects crystallisation of amorphous alloy influencing the phase composition of the products of this process.