玻璃转变时非晶合金微观结构演变的新进展

在玻璃转变时,金属玻璃只吸收少量热量(与结晶化相比)却引起其物理和力学性能的巨大变化.为了研究玻璃转变时的原子结构演变,采用原位同步辐射X射线的方法测定了在温度连续变化的情况下Zr-Cu-Al金属玻璃的结构函数.纵观本研究:该材料原子级的热膨胀比宏观热膨胀要小,而且在玻璃转变温度以上时明显增大;超过玻璃转变温度时,最近邻原子对中键长较长的原子对数量的变化率!N/N0(N0代表原子对的数量)明显变大.此类现象既可以用我们建立的过渡区链接团簇的非晶原子结构模型解释,又有力地支持此模型.该模型包含三个主要部分:1)原子紧密结合的团簇;2)团簇之间的自由体积;3)连接团簇的过渡区.

The Evolution of Atomic Structure during the Glass Transition

The glass transition involves a minor change in the internal energy, and yet the physical and mechanical properties of a glass change dramatically. In order to determine the evolution of the atomic structure through the glass transition, in-situ synchrotron X-ray scattering measurements as a function of temperature on metallic glass were conducted. It is found that the thermal expansion at the atomic level is smaller than the macroscopic thermal expansion, and significantly increases above the glass transition temperature (Tg). It is also found that the relative change of the quantity(N represents the number of atom pairs), with significantly longer interatomic distances for the nearest atomic pairs, increases above Tg. These phenomena consist with the interconnecting zone connected tight-banded-cluster amorphous model. This model contains essentially three major parts: (I) clusters with tight bonding; (II) loosely bonded free volume regions between clusters; and (III) interconnecting zones, which interconnect the clusters.