Improved prediction of the grain size of aluminum alloys that includes the effect of cooling rate

A comprehensive study of the effect of cooling rate on the grain size of a range of grain refined wrought aluminum alloys was carried out under quiescent solidification conditions where nucleation occurs predominantly by a constitutional undercooling mechanism. Increasing the cooling rate reduced the grain size by increasing the number of particles that nucleate grains and by affecting the development of constitutional undercooling. Both effects are represented using simple analytical relationships. By coupling these results with earlier work, an empirical relationship is developed between grain size, density of nucleant particles, cooling rate, nucleant potency and alloy composition that allows prediction of grain size across a wide range of alloys and cooling rates.