Large increase in fracture resistance of stishovite with crack extension less than one micrometer
Large increase in fracture resistance of stishovite with crack extension less than one micrometer
复制标题
裂纹扩展小于一微米的石英石的断裂抗力大幅提高
作者：
Kimiko Yoshida;F. Wakai;N. Nishiyama;Risako Sekine;Y. Shinoda;T. Akatsu;T. Nagoshi;M. Sone
开发高强度、韧性和耐损伤陶瓷需要纳米/微观结构设计，以利用不同长度尺度的增韧机制。目前已知的增韧机制在微观尺度上是有效的，因此，它们需要裂纹扩展到几微米以上才能增加抗断裂能力。在此，我们开发了一种微悬臂梁试样的微力学测试方法，以确定纳米晶SiO2斜长石的电阻曲线的早期部分，该部分表现为断裂诱导非晶化。我们发现这种新的增韧机制即使在纳米尺度上也是有效的，这是由于几十纳米的窄转变区宽度和与晶体向非晶态转变相关的大膨胀应变（从60到95%）。这种测试方法将成为一种强大的工具，用于寻找可能在纳米尺度上运行的增韧机制，以获得结构材料的可靠性和强度。
The development of strong, tough and damage-tolerant ceramics requires nano/microstructure design to utilize toughening mechanisms operating at different length scales. The toughening mechanisms so far known are effective in micro-scale, then, they require the crack extension of more than a few micrometers to increase the fracture resistance. Here, we developed a micro-mechanical test method using micro-cantilever beam specimens to determine the very early part of resistance-curve of nanocrystalline SiO2 stishovite, which exhibited fracture-induced amorphization. We revealed that this novel toughening mechanism was effective even at length scale of nanometer due to narrow transformation zone width of a few tens of nanometers and large dilatational strain (from 60 to 95%) associated with the transition of crystal to amorphous state. This testing method will be a powerful tool to search for toughening mechanisms that may operate at nanoscale for attaining both reliability and strength of structural materials.