Health & Environmental Research Online (HERO)


Print Feedback Export to File
7163034 
Journal Article 
Banding structure formation during directional solidification of Pb-Bi peritectic alloys 
Hu Xiao-wu; Li Shuang-ming; Ai Fan-rong; Yan Hong; , 
2012 
1 
Transactions of Nonferrous Metals Society of China
ISSN: 1003-6326 
ELSEVIER 
AMSTERDAM 
2131-2138 
WOS:000310564400012 
Directional solidification experiments on Pb-Bi peritectic alloys were carried out at very low growth rate (v=0.5 mu m/s) and high temperature gradient (G=35 K/mm) in an improved Bridgman furnace. The banding structures were observed in both hypoperitectic and hyperperitectic compositions (Pb-xBi, x=26%, 28%, 30% and 34%). Tree-like primary a phase in the center of the sample surrounded by the peritectic beta phase matrix was also observed, resulting from the melt convection. The banding microstructure, however, is found to be transient after the tree-like structure and only the peritectic phase forms after a few bands. Composition variations in the banding structure are measured to determine the nucleation undercooling for both alpha and beta phases. In a finite length sample, convection is shown to lead only to the transient formation of bands. In this transient banding regime, only a few bands with a variable width are formed, and this transient banding process can occur over a wide range of compositions inside the two-phase peritectic region.