Peritectic solidification of Cu-Sn alloys: Microstructural competition at low speed

Directional solidification experiments on Cu-Sn peritectic alloys have been conducted at very low velocity in a high-thermal-gradient Bridgman furnace. The size of the samples has been reduced in order to decrease natural convection and the associated macrosegregation. At the lowest growth rates (0.5 and 0.58 mu m s(-1)), eutectic-like alpha + beta lamellar structures have been observed in near-peritectic composition alloys over several millimeters of growth. These structures resulted from a destabilization of a band structure in which alpha- and beta-phases overlay each other. Electron backscattered diffraction measurements revealed that bands and lamellae of a solid phase are continuous and originate from a single nucleus. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.