It was recalled that, in 1984, grain boundary design - later known as grain boundary engineering - was proposed. The central premise of grain boundary engineering was that specific thermomechanical treatments, mainly on face-centred cubic materials which readily form annealing twins, could be used to improve resistance to various forms of intergranular degradation such as corrosion, cracking or embrittlement. Engagement with the concept has accelerated in recent years. This overview charts the progress of grain boundary engineering from its inception 25 years ago to the present day, including suggestions of key topics for ongoing or future research. These topics comprise confirmation of which boundaries were 'special' in terms of crystallography and properties, optimisation of processing regimes, new approaches to grain boundary engineering in systems without annealing twinning and incorporation of connectivity metrics, especially in three dimensions.

Grain Boundary Engineering: an Overview after 25 Years. V.Randle: Materials Science and Technology, 2010, 26[3], 253-61