Nonequilibrium Solidification Microstructure in Alloys

Abstract

Different microstructural features derive from the solidification process, according to the thermal and thermodynamic parameters involved, which can exhibit the characteristics of metastable structures or at least of structures rarely observed in industrial processes involving solidification. Usually the achievement of metastable structures is associated to high cooling rates (in the range 10⁷ – 10⁹ K/s), which can be attained in processes such as “Melt-Spinning” or “Laser-Glazing”. In both techniques a substrate, whose temperature is quite close to room temperature (and sometimes suitably cooled), plays the role of a cold thermal sink, whose heat capacity can be considered to be infinite if the energy values involved in the aforesaid techniques are considered. Indeed the melt layers which afford the aforesaid cooling rates to be reached are usually very shallow, ranging between 20 and 100 μm.