Induced Nucleation and Growth Mechanisms in Rapidly Solidified Alloys

Abstract

ABSTRACTAn attempt has been made to influence the trend of crystallization of a solidifying melt through the crystallization of an amorphous substrate undergoing transformation in its contact at the solid liquid interface. Two cases have been studied. In one case involving amorphous Cu60-Zr 40/Sn interface, it has been found that both textural and microstructural characteristics of the substrate, at the onset of the amorphous-crystalline transition, exert profound influence in crystallization, of the solidifying melt. High resolution electron microscopy and diffraction reveal that the preferred textural orienzation of the solidified tin is (111) at the interface and (100) far from the interface. In addition, an abundant array of edge dislocations found at the interface points to the role that these defects have played in the nucleation process of the solidifying melt. In the case of Ni60 Nb40/A1 the textural characteristics of the solidifying aluminum melt appear to be less perturbed by the crystallization effects of the substrate.