Challenges in the development of aluminium-based bulk amorphous alloys

The high tensile strengths of amorphous Al alloys (containing up to 90at% Al) make these alloys good candidates for high specific strength applications. The challenges continue to be both the high cooling rates necessary to produce the glassy structures which, to date, has limited the product to thin ribbons (or splats) and fine powders and the necessary consolidation into bulk volumes before application; with only a few exceptions, the consolidation process leads to devitrification and loss of the unique properties of the glass. This paper addresses this challenge by reviewing recent results aimed at (a) identifying new alloy compositions with high glass forming ability; (b) identifying new alloy compositions with extensive supercooled liquid regions; (c) improving the consolidation processes. For example, spray forming was recently used to process a partially amorphous 7 kg billet of Al₈₄Ni₅Y₉Co₂ indicating that it might be possible to produce Al-based bulk metallic glass using bulk processing schemes that have intermediate cooling rates. These results and their implications will be discussed.