液态扩散焊制备泡沫铝夹芯板及其疲劳行为

采用超声辅助液态扩散焊接的方法制备冶金复合泡沫铝夹芯板，利用光学显微镜（OM）和SEM观察冶金复合样品的界面组织和结构，发现连接界面发生了侵蚀作用，接头均匀连续；EDS线扫结果表明，连接界面处焊接合金（Zn-10Al）和铝基体间的元素扩散现象明显，表明在超声作用下，基体材料表面氧化膜被破坏，枝晶在界面附着生长，形成良好的冶金连接。将制备的冶金复合样品和胶黏泡沫铝夹芯板样品进行三点弯曲疲劳对比试验，结果显示，冶金复合样品和胶黏样品的疲劳极限分别达到3 058 N和2 829 N。在相同载荷下，冶金复合样品的疲劳寿命（S-N）远远长于胶黏样品。两种样品的疲劳破坏方式完全不同，胶黏样品表现为面板和芯层黏接面的脱黏剪切破坏，冶金复合样品的疲劳剪切破坏出现在泡沫铝芯层，没有出现面板脱离现象。

Fabrication and fatigue behavior of aluminum foam sandwich via liquid diffusion welding

Liquid diffusion welding method was used to prepare metallurgical bonding aluminum foam sandwich. The bonding interfacial microstructure was observed by optical microscope (OM) and SEM. Under the effect of ultrasonic vibration, the bonding seam is uniform and continuous. The ZnAl eutectic dendrite structure forms on the surfaces of Al foam core and Al sheet substrates. Furthermore, obvious erosion behavior can be seen on the bonding surfaces as ZnAl alloy filler melted. EDS line scan results show that the mutual diffusion of the main elements Zn and Al across the interface is extensive. All these characteristics imply that the oxide film on the substrates is destroyed and sound bonding achieves. Three point bending fatigue test was employed to the sandwich structure fatigue behavior. Comparing with the adhesive aluminum foam sandwich, the fatigue life (S-N) curves indicate that the metallurgical bonding samples have a better fatigue performance, and their fatigue limits are 3 058 N and 2 829 N respectively. Under the same load, the metallurgical bonding sample has much longer fatigue life than the adhesive sample. And the fatigue fracture mode for these two types samples are completely different in two ways, the failure mode for adhesive sample is shear debonding, but no debonding occurred for metallurgical bonding sample, which indicates that failure mode of metallurgical bonding sample due to foam core shear.