Cold spray deposition exploits the phenomenon of impact bonding for solid-state consolidation of metallic microparticles. However, the particle interfaces in the deposits are susceptible to crack propagation under mechanical stresses, which results in inferior ductility. In this work, we seek to develop insights into splat-substrate interface bonding by in-situ micromechanical investigations. A miniaturized mechanical testing approach is reported here, which relies on micromachining, targeted indentation, and real-time scanning electron microscopy to probe deformation and failure at buried interfaces. Investigations at the “single splat length scale” enabled us to distinguish deformation mechanisms associated with 6061Al splats with globular and pancake-shaped morphologies. We observed a transition from mechanical interlocking to metallurgical bonding with an increase in the degree of particle flattening during deposition. The mechanically interlocked splats debond from the substrate via crack propagation and splat sliding. On the other hand, metallurgically bonded splats do not fail under indentation stresses exceeding 380 MPa; instead, displaying shear band propagation and pile-up mechanisms. A four-fold enhancement in the critical stress for crack propagation in mechanically-interlocked splats is achieved after a two-step annealing-aging heat-treatment cycle. We demonstrate that interface bonding plays a more dominant role than the inherent plasticity of splats in influencing bulk deposits' ductility, underscoring the importance of interface engineering in cold sprayed materials.

冷喷涂沉积利用了金属微粒固态固结的冲击结合现象。然而，沉积物中的颗粒界面在机械应力下易受裂纹扩展的影响，从而导致延展性较差。在这项工作中，我们寻求通过原位微机械研究深入了解 splat-substrate 界面结合。这里报告了一种小型化的机械测试方法，它依赖于微加工、目标压痕和实时扫描电子显微镜来探测掩埋界面的变形和故障。在“单片长度尺度”上的研究使我们能够区分与球状和饼状形态的 6061Al 片相关的变形机制。我们观察到从机械互锁到冶金结合的转变，随着沉积过程中颗粒扁平化程度的增加。机械互锁的碎屑通过裂纹扩展和碎屑滑动从基材上脱离。另一方面，冶金结合的板条在压痕应力超过 380 MPa 时不会失效；相反，显示剪切带传播和堆积机制。经过两步退火-时效热处理循环后，机械互锁板条裂纹扩展的临界应力提高了四倍。我们证明了界面结合在影响大块沉积物的延展性方面比splats 的固有塑性起着更重要的作用，强调了界面工程在冷喷涂材料中的重要性。