ABSTRACT
Although grain growth is a commonly observed phenomenon in crystalline materials, there were instances when grain growth ceased for no obvious reason. This led to considerable speculation about a ‘limiting grain size’ in relation to the overall dimensions of the polycrystalline body. Such speculation has now been discarded now that a better understanding of the grain growth process has been obtained. On the other hand, the production of fine grained steels, using small aluminium additions, was common practice in the early 20th Century, (less than 50 years after Bessemer’s revolutionary introduction of bulk steel-making) even though the mechanism by which the aluminium refined the grain size was to remain a mystery for a further 50 years. It was left to Clarence Zener, a gifted physicist, to make the earliest description of the effect of second phase particles on the inhibition of grain growth (Zener, 1949). His contribution, and the subsequent developments, are described in this chapter.
