Invited Lecture
Phase separation and grain boundary segregation in sintering of nanocrystalline alloys

Consolidation of nanocrystalline powders is a promising route towards bulk nanocrystalline materials with exceptional mechanical properties. While their nanostructure offers the kinetic advantage of ultrafast mass transport through grain boundaries, their general lack of thermal stability must be remedied to avoid coarsening during sintering at elevated temperatures. In this talk we summarize our recent work on nanocrystalline alloys, which were designed to exhibit high thermal stability while being amenable to sintering. The complex microstructure evolution in these alloys will be discussed in terms of the competition between grain boundary segregation, phase separation and nano-scale oxidation. The diffusion mechanisms controlling the sintering process will be identified. Examples will be shown for a variety of alloy systems which can undergo consolidation to full density while retaining their nanocrystallinity.