Grain size gradient naturally prepared through recrystallization in rapidly solidified undercooled alloy melts

A grain size gradient was naturally prepared through recrystallization in rapidly solidified Ni80Cu20 alloys quenched before recalescence. The fine grains on the surface of quenched specimens were partially recrystallized. However, the coarse grains in the deeper layers of the quenched alloys were fully recrystallized. It is proposed that the grain size gradient is due to recrystallization in the microstructures of the quenched alloys. Annealing the microstructure on the surface of the quenched specimen led to crystal growth via recrystallization. These experimental results provided strong evidence for a grain refinement mechanism in undercooled solidification of alloys.