动态压缩下Zr基非晶合金失效释能机理

为研究Zr 基非晶合金动态压缩条件下的失效释能机理,采用力学试验机、霍普金森杆、高速摄影、差示扫描量热分析(differential scanning calorimetry, DSC)、扫描电镜(scanning electron microscope, SEM)等,得到了材料应力应变曲线、高速摄影图像、失效式样微观形貌及DSC 曲线,根据实验数据计算了材料的晶化激活能,并拟合了材料的JH-2(Johnson-Holmquist Ⅱ)模型,对材料动态失效过程进行有限元数值模拟。实验结果表明,压缩条件下材料为脆性断裂,断口处观察到典型的脉状纹样及液滴状结构,材料失效过程伴随着释能现象;数值模拟结果表明,材料裂纹局部的瞬时内能大于材料晶化激活能。动态压缩下材料的失效释能机理即为材料破碎释放储存的弹性势能,并导致材料局部晶化释能,释能强度与应变率成正相关。

Failure behavior and energy release of Zr-based amorphous alloy under dynamic compression

To study the mechanism of failure behavior and energy release mechanism of Zr-based amorphous alloys, Instron machine, split hopkinson bar, high-speed photography, DSC and SEM are used to achieve the stress-strain curves at low strain rate, stress-strain curves at high strain rate, failure processes, DSC curves and failure morphologies, respectively. The crystallization enthalpy is obtained from DSC curves. The stress-strain curves are fitted by the Johnson-Holmquist II model, and the finite element method using this model is executed to simulate the failure process of material under dynamic compression. The experimental results suggest that the material fractures brittle under compression. Typical vein-like pattern is observed at the fracture surface of the material. The energy releasing occurs simultaneously with the material failure. The simulation results reveal that the internal energy of local crack is higher than crystallization enthalpy of the material. The energy release of Zr-based amorphous alloys results in the elastic potential energy and crystallization energy released by the material with instantaneous crack. The strength of energy release is in direct proportion to strain rates.