强激光加载铝材料动态损伤特性及其微介观结构观测

在神光-Ⅱ装置上利用强激光加载铝材料进行高应变率(高于106s-1)层裂实验,研究不同初始温度下高纯铝材料的动态损伤特性。采用任意反射面速度干涉仪测量样品自由面速度剖面,由自由面速度剖面计算纯铝样品层裂强度与屈服应力。结果表明:随着温度升高,材料层裂强度减小,屈服应力增大。对激光加载前后样品进行金相分析,观察不同初始温度下纯铝材料的微介观结构变化及其损伤特性。结果表明:随着温度升高,样品晶粒尺度缓慢增大,但在873K(近熔点)时晶粒尺度急剧增加;层裂面附近小孔洞数目较多,孔洞尺寸也较大,而远离层裂面处,孔洞数目相对较少,且尺寸也较小;材料的断裂方式随温度升高由沿晶断裂为主逐渐变为穿晶断裂为主。

Characteristics of dynamic fracture of aluminum and metallographic analysis of recovered samples in laser experiments

High-power laser induced shocks were used to study spall fracture of polycrystalline aluminum at strain rates more than 106/s at Shenguang-Ⅱ laser facility. The free surface velocity histories of shock-loaded samples, 150 m thick and with initial temperature from 293 K to 873 K, were recorded using velocity interferometer system for any reflector (VISAR). From the free surface velocity profile ,spall strength and yield stress are calculated, which shows that spall strength declines while yield strength increases with initial temperature increasing. The loaded samples were recovered for metallographic analysis through Laser Scanning Confocal Microscopy. It is found that there are more micro-voids and more bigger voids near the spall plane. Meanwhile, the grain size increases with temperature slowly except the sharp change at 893K(near melting point). Besides, the fracture mechanisms change from mainly intergranular fracture to transgranular fracture with initial temperature increasing.