微量Cu元素对Au-24Ag-3.25Si钎料合金组织和焊接性能的影响

Effect of Minor Cu on Microstructure and Welding Performance of Au-24Ag-3.25Si Brazing Alloy

通过分析相图,配制成分分别为Au-24Ag-3.25Si、Au-24Ag-3.25Si-1.5Cu、Au-24Ag-3.25Si-2.0Cu、Au-24Ag-3.25Si-2.5Cu4种合金,中频感应真空熔铸法制备铸锭,在流动氢气保护管式电阻炉中进行焊接实验,基板采用纯Ni片,焊接温度为550℃。使用微量型DTA差热分析仪测定钎料合金的熔化温度,并通过金相观察和扫描电镜观察结合X射线能谱分析对钎料合金的组织和焊接性能进行研究。结果表明,添加适量的Cu元素能降低Au-24Ag-3.25Si钎料合金的熔点,减小固液相间隔;Cu元素的加入使Au-24Ag-3.25Si钎料合金的显微组织发生了显著变化,有新固溶体的形成,使得钎料合金的硬度随之升高;Au-24Ag-3.25Si-1.5Cu钎料合金与Ni焊接后铺展形貌良好,润湿角较小,其焊接界面组织形貌与未添加Cu元素前基本一致,仍然有金属间化合物层(IMC)出现,能谱分析和线扫描结果显示,该IMC层由Ni和Si的金属间化合物组成,Cu元素的添加没有明显改善Au-24Ag-3.25Si钎料合金与Ni的焊接性能。

By analyzing the phase diagram, four kinds of alloys with different component, Au-24Ag-3.25Si, Au-24Ag-3.25Si-1.5Cu, Au-24Ag-3.25Si-2.0Cu, Au-24Ag-3.25Si-2.5Cu（wt%） were prepared by the vacuum melting method in a medium-frequency induction furnace. The welding experiment was done in a tube type resistance furnace with flow H2 as protective gas, the welding temperature was 550 ℃ and the base plate is pure Ni sheet. The melting temperature was measured by a microscale DTA analyzer and the microstructure and welding performance of the brazing alloy were studied by metallographic and SEM analysis together with X-ray energy spectrum analysis. The results show that the addition of proper Cu can reduce the melting temperature and the interval between solidus and liquidus of the Au-24Ag-3.25Si brazing alloy. The microstrueture of the alloy was also changed greatly because of the addition of Cu. There is a new type of solid solution formed, which makes the microhardness of the alloy increased accordingly. The spreading pattern is fine and the wetting angle is small after the Au-24Ag-3.25Si-1.5Cu brazing alloy welding with Ni, whose welding interface structure is almost the same as that without Cu. There is also IMC layer in the interface and the X-ray energy spectrum analysis show that the IMC layer is Ni-Si intermetallic. The addition of Cu will not improve the welding performance of the Au-24Ag-3.25Si brazing alloy with Ni obviously.