过偏晶合金中异常Cu-Sn壳/Pb核宏观结构的形成

Formation of anomalous CuSn-shell/Pb-core macrostructure in Cu-Sn-Pb hypermonotectic alloys

摘要:

目前核壳结构难混熔合金的壳是由低熔点相组成还是高熔点相组成，尚无确切答案。根据文献中Cu-Sn-Pb合金的计算相图，通过铸造法研究14Sn-73.1Cu-12.9Pb、14Sn-64.5Cu-21.5Pb、Cu-65Pb和Cu-75Pb合金的相分离过程，结果表明，14Sn-64.5Cu-21.5Pb合金具有富Cu-Sn相包裹富Pb相核壳结构组织；这一结果与低熔点相（如Cu-75Pb合金）形成核的观点不一致，这种异常现象可以解释为：在铸造过程中，由于过冷度的影响，偏晶反应发生在液相分离反应前。这为通过控制凝固路径改变难混熔合金的结构提供了一种可能的方法。

Abstract:

For the core-shell structured immiscible alloys within the immiscible gap, whether the shell is composed of a phase with lower or higher melting point, there is no exact answer yet. Based on the Cu-Sn-Pb calculated phase diagram given by reference, the phase separation of 14Sn-73.1Cu-12.9Pb, 14Sn-64.5Cu-21.5Pb, Cu-65Pb and Cu-75Pb alloys have been experimentally investigated by casting method. An anomalous core-shell structure with a CuSn-rich shell and a Pb-rich core formed in 14Sn-64.5Cu-21.5Pb alloy, which differed from the viewpoint that a lower melting point phase generally formed the shell as Cu-75Pb alloy showed. This anomalous phenomenon may be explained by that the liquid separation reaction was suppressed due to undercooling generated during casting process and the monotectic reaction took place before the liquid separation reaction. This work may provide a method to modify the structure of immiscible alloys through controlling solidification path.