压痕塑性变形诱导非晶合金的晶化

Indentation-induced crystallization in a metallic glass

利用透射电镜研究了Zr65Al7.5Ni10Cu12.5Ag5非晶合金的Vickers压痕内微观结构的变化.结果发现,压痕塑性变形诱导非晶合金发生了晶化,在压头棱角下面的区域内有尺寸大于1μm的晶体析出.选区电子衍射分析表明,该析出相是稳定的CuZr2或NiZr2四方晶体,而没有析出该非晶合金在加热过程中的初生相二十面体准晶相,说明非晶合金的机械稳定性与热稳定性是有区别的.打压痕过程中的温度升高是可以忽略的,本工作进一步证实了塑性变形诱导非晶合金晶化的主要动力是粘性流动而非局部热效应.

The microstructure change in the Vickers indent of the Zr65Al7.5Ni10C11 12.5Ag5 metallic glass at room temperature is investigated by transmission electron microscopy. It is found that the indentation-induced crystallization occurs namely underneath the indenter edges, where viscous flow is involved and crystals with the size larger than 1 μm appear. The selected area electron diffraction shows that the crystalline phases are stable tetragonal CuZr2 or NiZr2, but not the icosahedral one that grows as metastable phase on heating. The local temperature rise during indentation can be ignored, which further suggests that the mechanically induced crystallization in a metallic glass is attributed to the viscous flow rather than the local heating effect.