Initiation and evolution of fatigue cracks at the interfaces in three-layer Zr–Ti/Zr–Steel composites is herein examined by in situ optical microscopy for the first time. Specimens cut out from three composite plates comprising Zr 700, Ti Gr. 1, and P265GH steel layers have been subjected to uniaxial fatigue cyclic loading. It is found that mechanical property mismatch between layers and defects at the interfaces can reduce the fatigue life of composite plates. An insight into the evolution of cracks initiated at the interfaces reveals that (1) most of the cracks grow into adjacent layers along two distinct planes, and (2) these cracks could lead to the fatigue failure of composites. One of these planes coincides with the adiabatic shear band orientation found in Ti Gr. 1 and Zr 700 layers. The interfaces in multilayer metallic composite could have excellent fatigue strength depending on their structural properties.

本文首次通过原位光学显微镜检查了三层Zr-Ti / Zr-Steel复合材料界面处疲劳裂纹的产生和演化。从三个复合板（包括Zr 700，Ti Gr）切出的样品。在图1中，P265GH钢层已经经受了单轴疲劳循环载荷。发现层之间的机械性能失配和界面处的缺陷会降低复合板的疲劳寿命。对在界面处产生的裂纹演变的深入了解表明：（1）大多数裂纹沿两个不同的平面生长到相邻的层中；（2）这些裂纹可能导致复合材料的疲劳破坏。这些平面之一与Ti Gr中的绝热剪切带方向一致。1和Zr 700层。