Rapidly Solidified Structures of Al-0.5 mass%Cu Alloy Obtained by High Power CO₂ Laser Grazing

Abstract

Al-Cu alloy with low solute concentration 0.5 mass%Cu is rapidly melted by CO₂ laser with high power and solidified unidirectionally with high scanning rate and high cooling rate. Solidification rate and temperature gradient are analyzed numerically by the finite element code MARC. The rapidly solidified dendritic microstructures have been observed in the wide range of growth rates, which have been predicted by the Mullins-Sekerka’s theory. The primary dendrite arm spacing is shown to decrease with V^0.5 below 0.1 m/s of growth rate V and to decrease more slowly than V^0.5 over 0.1 m/s growth rate.