Growth of Pb—Bi peritectic alloys at moderate and high values of G/R

Steady and unsteady state peritectic solidification

“…By varying the solidification thermal parameters, such as the growth rate (V L ) and temperature gradient ahead the liquidus front (G L ), distinct microstructures can be formed, such as banded and cellular structures in Sn-Cd, 14 Cu-Sn, 4 Pb-Bi 15 and Fe-Ni 16 alloys; cellular and plate-like structures in Fe-Ni alloys; 16,17 and banded, cellular/dendritic and lamellar structures in Ti-Al alloys. 12,18 Many technologically important alloys such as peritectic steels are manufactured by continuous casting-a process with a wide range of inherent cooling rates; 19,20 Ti-Al peritectic alloys by laser melting-an ultrahigh temperature gradient direction solidification process 11 ; and Zn-Ag hyperperitectic alloys by melt spinning-a rapid solidification process 22 -all of them unsteady solidification processes, which remarkably affect the properties of these materials. However, most of the previous investigations on peritectic solidification existing in the literature involve experimental studies of steady state Bridgman type growth.…”

“…Although some recent studies involving peritectic Pb-Bi alloys have been reported, none of them encompassed unsteady solidification conditions. Shcherbakov et al 22 used a zone melting technique, which permitted independent control of the thermal gradient, G L , and the growth rate, V L , to investigate the growth of Pb-Bi peritectic alloys at moderate and high values of G L .V L 21 . They reported that the solidification microstructures depended strongly on the composition and the value of G L .V L 21 , i.e.…”

“…Many technologically important alloys such as peritectic steels are manufactured by continuous casting—a process with a wide range of inherent cooling rates; 19,20 Ti–Al peritectic alloys by laser melting—an ultrahigh temperature gradient direction solidification process 11 ; and Zn–Ag hyperperitectic alloys by melt spinning—a rapid solidification process 22 —all of them unsteady solidification processes, which remarkably affect the properties of these materials. However, most of the previous investigations on peritectic solidification existing in the literature involve experimental studies of steady state Bridgman type growth.…”

Solidificação unidirecional transitória de ligas peritéticas do sistema Pb-Bi

“…Para a liga Pb-26%Bi, nas condições de solidificação em processo de refrigeração à água e muito rápido, o mesmo resultado foi constatado na análise por microscópio, ou seja, presença de fases  + Para o processo de solidificação com resfriamento em forno desta liga e posterior análise em microscópio, as fases identificadas foram  + sendoa mistura eutética dee.Porém na análise por Raios-X as microestruturas verificadas, para esses três processos de solidificação, foram  + sendo a fase contituída por solução sódida de Pb em Bi). Os estudos realizados por Shcherbakov et al (1974), em condições de moderado e alto valor de G/V para a liga Pb-26%Bi, apresentaram resultados muito similares aos de Tiwari et al (1970). As microestruturas se caracterizaram por morfologia dendrítica (ramificada ou não) e as fases identificadas também formam uma mistura de  +  é a solução sólida rica em Pb e  é o produto peritético).…”