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首页> 外文期刊>Journal of Materials Research >Spherical nanoindentations and kink bands in Ti_3SiC_2
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Spherical nanoindentations and kink bands in Ti_3SiC_2

机译：Ti_3SiC_2中的球形纳米压痕和扭结带

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We report on load versus depth-of-indentation response of Ti_3SiC_2 surfaces loaded with a 13.5 (mu) m spherical tipped diamond indenter up to loads of 500 mN. Using orientation imaging microscopy, two groups of crystals were identified; one in which the basal planes were parallel to, and the other normal to, the surface. When the load-penetration depth curves were converted to stress-strain curves the following was apparent: when the surfaces were loaded normal to the c axis, the response at the lowest loads was linear elastic-well described by a modulus of 320 Gpa-followed by a clear yield point at approximately 4.5 GPa. And while the first cycle was slightly open, the next 4 on the same location were significantly harder, almost indistinguishable, and fully reversible. At the highest loads (500 mN) pop-ins due to delaminations between basal planes were observed. When pop-ins were not observed the indentations, for the most part, left no trace. When the load was applied parallel to the c axis, the initial response was again linear elastic (modulus of 320 GPa) followed by a yield point of approximately 4 GPa. Here again significant hardening was observed between the first and subsequent cycles. Each cycle resulted in some strain, but no concomitant increase in yield points. This orientation was even more damage tolerant than the orthogonal direction. This response was attributed to the formation of incipient kink bands that lead to the formation of regular kink bands. Remarkably, these dislocation-based mechanisms allow repeated loading of Ti_3SiC_2 without damage, while dissipating significant amounts of energy per unit volume, W_d, during each cycle. The values of W_d measured herein were in excellent agreement with corresponding measurements in simple compression tests reported earlier, confirming that the same mechanisms continue to operate even at the high ((approx =)9 GPa) stress levels typical of the indentation experiments.
机译：我们报道了负载为13.5（μm）球形尖头金刚石压头的Ti_3SiC_2表面在最大500 mN的载荷与压痕深度响应的关系。使用取向成像显微镜，鉴定出两组晶体；即晶体。一个基面平行于表面，另一个垂直于表面。当将载荷-穿透深度曲线转换为应力-应变曲线时，很明显：当表面垂直于c轴加载时，在最低载荷下的响应为线性弹性井，其模量为320 Gpa，其后为约4.5 GPa的清晰屈服点。尽管第一个周期稍微开放，但接下来的4个在同一位置上却要困难得多，几乎无法区分并且完全可逆。在最高载荷（500 mN）下，观察到由于基底平面之间的分层而弹出的弹跳。当没有观察到弹出窗口时，压痕在大多数情况下都没有留下痕迹。当平行于c轴施加载荷时，初始响应再次为线性弹性（模量为320 GPa），然后是大约4 GPa的屈服点。在这里，在第一个和随后的循环之间再次观察到明显的硬化。每个循环导致一些应变，但屈服点没有随之增加。该方向甚至比正交方向更能容忍损坏。该反应归因于初始扭结带的形成，其导致规则扭结带的形成。值得注意的是，这些基于位错的机制允许重复加载Ti_3SiC_2而不会造成损坏，同时在每个循环中耗散大量的每单位体积W_d的能量。本文测得的W_d值与早先报道的简单压缩测试中的相应测量值非常吻合，证实了即使在压痕实验中典型的高应力水平（约9 GPa）下，相同的机理仍继续起作用。

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