The tension field created by a spherical nucleus freezing into its less dense undercooled melt

Grain refinement in the solidification of undercooled Ni–Pd alloys

“…For the alloy with a solidification temperature range, there exists two undercooling regions in which the grains are considerably refined. The proposed mechanisms for the grain refinements consist of (1) copious nucleation ahead of the solidification front induced by a pressure pulse [2][3][4], (2) recrystallization following solidification [5,6], and (3) dendrite break-up either mechanically or by remelting [7,8]. However, these mechanisms suffer from a limitation that they cannot simultaneously explain the double grain refinements.…”

Microstructure evolution in undercooled Fe-7.5at% Ni alloys

“…An important outcome of high undercooling experiments is the observation of ''refined equiaxed grains microstructure''. Since the first detection of grain refined processing by Walker [2] in undercooled Ni melts in 1956, such a transition has been observed in many metallic systems [3][4][5] and different mechanisms have been proposed to explain this phenomenon, such as cavitations in the melt [6], dendrite remelting [7], stress brokenup and recrystallization [8], fluid flow effects [9], relationship between break up time and postrecalescence time [5,10] and the development of growth instabilities [11].…”

The mechanism for spontaneous grain refinement in undercooled pure Cu melts

“…These include cavitation in the melt [4], fluid flow effects [5], dendrite re-melting [6], recrystallisation [7] and the development of growth instabilities [8].…”