非晶合金中剪切温升的研究进展

A Brief Overview of Temperature Rises During Shear Banding in Bulk Metallic Glasses

区别于传统的晶态金属材料,非晶合金(BMGs)不具备长程有序结构,其塑性变形载体为剪切带。剪切带一旦形成,便很快发展成为裂纹,引发材料的灾难性断裂。剪切不稳定性的研究有助于非晶合金塑性变形机理的理解,并可为非晶合金塑性变形能力的提高提供设计思路。近年来,基于非晶合金的结构特点,科研工作者努力探究非晶合金的剪切不稳定性,主要提出了结构软化诱导的剪切不稳定性和热软化引发的剪切不稳定性两种机制。本文重点总结了非晶合金中剪切温升的研究进展,介绍了测试应变速率、外部约束、试验机刚度和测试温度对剪切温升的影响,指明非晶合金中剪切引入的热远低于玻璃转变温度,暗示热软化对剪切不稳定性的影响是微弱的。本文最后对非晶合金中剪切不稳定性机制的研究方向进行了展望。

Bulk metallic glasses (BMGs) possess amorphous structure that lacks long-range orders. In contrast to crystal metals, shear banding is ge- nerally believed to be a common plastic deformation mode at temperatures far below glass transition temperature for monolithic BMGs. While shear bands can accommodate some plastic strain, they would evolve into cracks to cause the catastrophic fracture of BMG samples. The investigation of shear-banding instability contributes to the understanding of plastic deformation mechanisms and further provides insights on strategies for improving the plastic deformation capability of BMGs. It is reported that structural softening and thermal softening are two potential origins of shear-banding instability in BMGs. In this review, we summarize the investigations on the shear heating mainly from four aspects, including temperature rises depending on testing strain rates, the external confinement, testing-machine stiffnesses, and testing temperatures. Finally, we discuss some key issues on the investigation of temperature rises and provide research topics for understanding shear-banding instability.