Brittle film-induced cracking of ductile substrates
Brittle film-induced cracking of ductile substrates
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DOI：
10.1016/j.actamat.2015.07.059
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发表时间：
2015-10
期刊：
影响因子：
9.4
通讯作者：
Tao Guo;L. Qiao;Xiaolu Pang;A. Volinsky
中科院分区：
文献类型：
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作者：
Tao Guo;L. Qiao;Xiaolu Pang;A. Volinsky
薄膜和基材的机械完整性对于整个系统的性能至关重要。在本研究中，黄铜韧性基板开裂的脆性TiN膜断裂诱导观察。与直觉相反，脆性薄膜不会保护韧性基底，而是会导致其过早断裂，正如这里的实验所证明的那样。在相当低的应变水平下，脆性薄膜断裂可导致韧性基体开裂。基于裂纹扩展过程中能量守恒的解析计算解释了这种膜致裂纹现象。结果表明，穿透到基体中的裂纹深度是裂纹速度和从裂纹尖端发射的位错数的函数。相对较厚的脆性膜和快速扩展的裂纹有利于韧性基底的断裂。导致黄铜基体开裂的临界裂纹速度为61 m/s。脆性膜的存在不仅可以阻止位错从晶体表面逃逸，抑制位错源的位错发射，而且由于脆性断裂，还可以引发高速的通道裂纹。这两种因素都对软黄铜基体中的裂纹扩展有促进作用。这项研究提供了另一种观点的概念，脆性膜可以保护韧性基板免受损坏。
Film and substrate mechanical integrity is essential for the whole system’s performance. In the present study, cracking of brass ductile substrate induced by brittle TiN film fracture was observed. Counter-intuitively, instead of protecting the ductile substrate, a brittle film can cause its premature fracture, as demonstrated here experimentally. Brittle film fracture could induce cracking of ductile substrate at considerably low strain level. Analytical calculation based on energy conservation during crack propagation is presented to explain this phenomenon of film-induced cracking. It is shown that crack depth penetrated into the substrate is a function of both crack velocity and the number of dislocations emitted from the crack tip. Relatively thick brittle films and fast propagating cracks favor fracture of the ductile substrates. The critical crack velocity, which can induce the cracking of brass substrate, is 61 m/s. The presence of brittle film could not only prevent dislocations escaping from the surface of the crystal and inhibit dislocations emitting from surface dislocation sources, but also initiate a channel crack with high velocity due to brittle fracture. Both of them contribute to crack propagation in soft brass substrate. This study provides an alternative view to the notion that a brittle film can protect the ductile substrate from damage.