真空感应熔炼Cu-15Ni-8Sn合金铸锭的铸态组织与Sn宏观偏析研究

Study on As cast Microstructure and Macro Segregation of Sn in Cu-15Ni-8Sn Alloy Ingot Produced by Vacuum Induction Melting

采用真空感应熔炼制备了Cu-15Ni-8Sn合金铸锭,分析了合金的铸态组织和Sn的宏观偏析。结果表明,合金铸锭上、中部薄片试样的柱状枝晶发达,二次枝晶间距大,缩孔、疏松缺陷严重,下部薄片试样无缩孔、疏松缺陷,以致密、细小的等轴晶区为主,二次枝晶间距小;合金的铸态组织由贫Sn的α相、富Sn的片层状α+相、富Sn的小块骨状相组成;铸锭表面Sn的反偏析显著,铸锭上、中横截面的Sn含量由中心至表面的Sn含量逐渐增加,铸锭下横截面由中心至表面的Sn含量基本接近,波动不大,但中心附近的Sn含量反常偏高。铸锭上横截面的Sn偏析程度明显大于铸锭中、下横截面的偏析程度;铸锭的Sn宏观偏析导致了不同位置的维氏硬度差异明显。

The Cu-15Ni-8Sn alloy ingot were prepared by vacuum induction melting.The as cast microstructure and the macro segregation of Sn were analyzed.The results showed that the columnar dendrites of the upper and middle thin samples of the alloy ingot are developed,the secondary dendrite spacing is large,the shrinkage and porosity defects are serious,the lower thin samples are free of shrinkage and porosity defects,and the dense and fine equiaxed crystal areas are dominant,the secondary dendrite spacing is small;The as cast structure of the alloy consists ofαPhase,Sn rich lamellarα+Phase,Sn rich small bone Phase;The anti segregation of Sn on the ingot surface is significant.The Sn content of the upper and middle cross sections of the ingot gradually increases from the center to the surface.The Sn content of the lower cross section of the ingot is basically close from the center to the surface,with little fluctuation,but the Sn content near the center is abnormally high.The segregation degree of Sn in the upper cross section of the ingot is obviously greater than that in the middle and lower cross sections of the ingot;The macro segregation of Sn in ingot leads to the inconsistency of Vickers hardness at different positions.