The work performed during the project thus far, includes the design, preparation, processing and investigation of Iron-based nanocrystalline alloys in powder form. In particular, we have found several alloying candidates for Iron that should lead to a stable nanostructure, and have then narrowed-down this list based on practical considerations, such as safety of use, cost, etc. Ultimately we have studied two primary alloys - Iron-Magnesium (Fe-Mg) and Iron-Gold (Fe-Au). We studied the alloying process, performed by ball milling, as well as the consequent thermal stability using various microscopy methods, to observe the nanostructure of the material, as it evolves with time and temperature. We identified the stabilizing mechanism(s) in each case, and have optimized the alloy composition. We then moved on to study the sintering (agglomeration) of the powders into a dense, nanocrystalline metal part. For Fe-Mg, we have added Chromium, creating a ternary Fe-Mg-Cr alloy with excellent thermal stability, and good sintering characteristics. In the case of Fe-Au, we found that, as expected, this alloy is highly sinterable without any further additions. A central results of our work is that we were able, for the first time, to design and prepare a nanocrystalline alloy which decreases its grain size to a lower (but stable) value, with an increase in temperature. This results side-steps a basic paradigm of materials science: "grains always grow with increased thermal exposure". This unique result has been published in the prestigious journal, Physical Review Letters (PRL). One final results we obtained was that, again, contrary to common thinking, mechanical alloying during ball milling does not always result in a homogenous alloy - it is quite possible to attain a nanocrystalline alloy with grain boundary segregation already in the as-milled state. This is a unique finding which we explained by studying the competition between ballistic and thermal diffusion, and published in the journal Scripta Materialia.
