高熵合金(CoCrFeMnNi)/铜真空扩散连接的界面行为及接头性能研究

Interfacial Behavior and Joint Performance of High-entropy Alloy CoCrFeMnNi and Pure Cu Joints Obtained by Vacuum Diffusion Welding

用固态扩散方法实现了CoCrFeMnNi高熵合金与铜在温度750~850℃下的良好连接,利用扫描电镜(Scanning electron microscope,SEM)、能谱(Energy disperse spectroscopy,EDS)分析、显微硬度测试及拉伸试验研究扩散反应温度对其界面反应行为和接头力学性能的影响,结合菲克扩散第二定律计算和分析Cu原子在高熵合金中的扩散系数。结果表明:Cu在高熵合金一侧的扩散速率大于高熵合金组元在Cu侧的扩散,随温度增加,高熵合金组元向Cu侧扩散时其在扩散区内原子浓度分布降低的程度按Mn>Cr>Fe>Co>Ni的顺序依次减小。理论计算表明,Cu在高熵合金中的平均扩散系数明显小于铜在不锈钢中的平均扩散系数。经扩散反应后,Cu/高熵合金界面附近均可形成FCC型固溶体组织的反应层,无金属间化合物产生。所有扩散连接接头拉伸后其断裂均发生在远离界面的铜侧,随扩散焊温度升高,其抗拉强度和应变有所降低,其中750℃时铜的抗拉强度与应变分别达到最大值224MPa和33%。

A good bonding between the high-entropy alloy （HEA ）CoCrFeMnNi and pure Cu is obtained at 750-850℃ by vacuum solid-state diffusion welding. The influence of bonding temperature on the interfacial behavior and the joints mechanical properties is investigated by scanning electron microscopy, energy disperse spectroscopy, microhardness test and tensile test. The diffusion coefficient of Cu in CoCrFeMnNi HEA is calculated and analyzed by fick＇s second law. The results show that the diffusion rate of Cu in HEA side is faster than that of HEA elements in Cu side and,as increasing with the temperature , the reduce extent of the HEA elements concentration distribution in the diffusion area agree with the sequence of elements in the order of Mn〉Cr〉Fe〉Co〉Ni. Theoretical calculations show that the average diffusion coefficient of Cu in HEA is significantly lower than those in the reference stainless steel. After diffusion bonding, a reaction layer consisted with FCC solid solution is formed in the interface region of all the joints, and there is no intermetallic compounds appeared. All the joints fracture occurred only in Cu sides far away from the interface, the tensile strength and strain all decrease as the bonding temperature increase. In the bonding temperature of 750℃, the tensile strength and strain reach its maximum value of 224 MPa and 33%, respectively.