The control of brittleness and development of desirable mechanical properties in polycrystalline systems by grain boundary engineering

Grain boundaries can be effectively controlled to produce or enhance their beneficial effects and also to diminish or reduce their detrimental effects on bulk properties in polycrystalline materials. Particular attention has been paid to the control of intergranular brittleness which remains a serious problem of material processing and development. Recent studies are presented and discussed, which have been successfully performed to control intergranular brittleness of "intrinsically brittle" materials such as the refractory metal molybdenum and the ordered intermetallic alloy Ni3Al and to produce superplasticity in an Al-Li alloy, by grain boundary engineering through controlling a new microstructural factor termed the grain boundary character distribution (GBCD). The optimization of GBCD and the grain boundary connectivity has been found to be a key to produce desirable bulk mechanical properties in both structural and functional polycrystalline materials. (C) 1999 Acta Metallurgica he. Published by Elsevier Science Ltd. All rights reserved.