稀土元素镧对Cu-15Ni-8Sn合金组织及性能的影响

Effect of rare earth lanthanum on microstructure and properties of Cu-15Ni-8Sn alloy

采用金相显微镜、扫描电镜和X射线衍射分析研究添加稀土元素镧(La)及其添加量对Cu-15Ni-8Sn合金组织及性能的影响。研究结果表明,添加微量La元素可以细化枝晶组织,改善合金的枝晶偏析,并且随着La添加量增加,改善效果越明显。La可与Ni或Sn反应形成LaNiSn相或La_(5)Sn_(3)相,并且随着La添加量增加,析出相逐渐由LaNiSn相向La_(5)Sn_(3)相转变。添加0.8%(质量分数,下同)La可以有效抑制形成不连续沉淀,分布在晶界上的La_(5)Sn_(3)相可以占据不连续沉淀的形核位点,分布在晶体内的La_(5)Sn_(3)相可以抑制不连续沉淀前沿界面的移动,共同作用抑制了Cu-15Ni-8Sn-0.8La合金时效过程中不连续沉淀的形成。此外,Cu-15Ni-8Sn-0.8La合金在450℃时效30 min获得HV硬度峰值为324。

The effects of lanthanum(La)on the microstructure and characteristics of Cu-15Ni-8Sn alloy were studied using metallographic microscopy,scanning electron microscopy,and X-ray diffraction analysis.The results showed that adding trace La could refine the dendritic organization and improve dendrite segregation,and the more the La content increased,the better the effect.La could combine with Ni and Sn as the LaNiSn phase or La_(5)Sn_(3) phase.When the La content increased,the precipitated phase gradually shifted from LaNiSn to La_(5)Sn_(3).Adding La(0.8%,w/w)could successfully prevent the formation of discontinuous precipitation.The La_(5)Sn_(3) phase distributed on the grain boundaries could occupy the nucleation sites of discontinuous precipitates,and the La_(5)Sn_(3) phase distributed within the grain could inhibit the movement of the interface at the front of discontinuous precipitates,thereby inhibiting the formation of discontinuous precipitates during the aging of the Cu-15Ni-8Sn-0.8La alloy.In addition,a HV peak hardness of 324 was obtained for the Cu-15Ni-8Sn-0.8La alloy by aging at 450℃ for 30 min.