Microstructural characteristics of laser-rapidly solidified aluninum alloys of single crystals Available to Purchase

In order to obtain a better understanding of rapid solidification and microsegregation, pulsed YAG laser was irradiated to melt pure 99.99%Al, Al-2%Cu and Al-9%Zn single crystals with specific surfaces of (001) and (011) crystallo-graphic planes. Microstructural characteristics of planar, cellular and cellular dendritic growth in laser spot welds were clarified in terms of alloy composition, crystallographic orientation and heat flux. In pure Al cellular growth occurred against the heat flux, but in aluminum alloys cellular dendrites grew straight along <100> crystallographic orientation. Growth rate of solid/liquid interface increased gradually upwards in the fusion zone, reaching 1 to 5 m/s. Accordingly, the primary arm spacing became smaller to about 0.5 μm in any alloy. Cu and Zn contents in cell cores in YAG laser spot welds were slightly smaller than their nominal composition, but were by far higher than those in GTA spot welds. However, phases enriched with a large content of Cu and Zn were localized at the corners toward <110> orientation from the cell core. This was interpreted in terms of the effect of rapid solidification and two-dimensional segregation behavior.