Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, 8700, Leoben, Austria.
School of Natural Sciences, Far Eastern Federal University, Vladivostok, 690950, Russia.
Nat Commun. 2018 Apr 6;9(1):1333. doi: 10.1038/s41467-018-03744-5.
The large plasticity observed in newly developed monolithic bulk metallic glasses under quasi-static compression raises a question about the contribution of atomic scale effects. Here, nanocrystals on the order of 1-1.5 nm in size are observed within an Fe-based bulk metallic glass using aberration-corrected high-resolution transmission electron microscopy (HRTEM). The accumulation of nanocrystals is linked to the presence of hard and soft zones, which is connected to the micro-scale hardness and elastic modulus confirmed by nanoindentation. Furthermore, we performed systematic simulations of HRTEM images at varying sample thicknesses, and established a theoretical model for the estimation of the shear transformation zone size. The findings suggest that the main mechanism behind the formation of softer regions are the homogenously dispersed nanocrystals, which are responsible for the start and stop mechanism of shear transformation zones and hence, play a key role in the enhancement of mechanical properties.
新开发的整体块状金属玻璃在准静态压缩下表现出的较大的塑性，引起了人们对原子尺度效应贡献的质疑。在这里，利用相衬高分辨透射电子显微镜（HRTEM）观察到了尺寸在 1-1.5nm 数量级的纳米晶。纳米晶的积累与硬区和软区的存在有关，这与纳米压痕法所确认的微尺度硬度和弹性模量有关。此外，我们还对不同样品厚度的 HRTEM 图像进行了系统的模拟，并建立了一个用于估计剪切转变区尺寸的理论模型。研究结果表明，形成较软区域的主要机制是均匀分散的纳米晶，它们负责剪切转变区的开始和停止机制，因此，在提高力学性能方面起着关键作用。
