石墨/紫铜低温连接接头界面组织和性能分析

Analyses of interfacial microstructures and mechanical properties of low-temperature bonded copper/graphite joints

采用表面反应金属化的方法实现了石墨与紫铜的低温连接。研究了温度对金属化层形貌的影响,同时对紫铜/石墨接头的力学性能进行了测试。在金属化过程中,Cr元素与石墨反应生成Cr_3C_2反应层,为得到以β-Sn为基体的金属化层提供必要条件。高的金属化温度,加强了Cr与石墨的反应速率,界面反应层逐渐由不连续变为连续状态,且厚度逐渐增加至2μm。接头的典型界面结构为:紫铜/Cu_6Sn_5/β-Sn/Cr_3C_2/石墨。随着时间延长,钎缝厚度逐渐减小,抗剪强度先增加后减小。接头全部断裂于石墨基体中,时间为80 s时得到的钎缝厚度最有利于缓解应力,此时得到最大的抗剪强度约25 MPa。

Graphite was bonded to copper at low temperature by a surface-reaction metallization method. The effect of temperature on the morphography of metallization layer was studied,also the mechanical properties of bonded copper/graphite joints were tested. In metallization process,Cr element reacts with graphite to form Cr3C2 interfacial layer,which makes it possible to obtain a metallization layer in β-Sn matrix.With the increase of temperature,the reaction between Cr and graphite is enhanced,which results in that discontinuous interfacial layer becomes continuous and its thickness increases to 2 μm. The typical interfacial microstructures of joint are copper/Cu6Sn5/β-Sn/Cr3C2/graphite. At longer holding time,the thickness of bonded seam decreases,whereas the shear strength increases first and then decreases. All of the joints fracture in graphite substrate in tests. The highest shear strength of 25 MPa is achieved at 80 s and the proper seam thickness has the most favorable effort to release the residual stress.