Impact response and microstructural characteristics of 6061-T6 aluminum alloy at cryogenic temperatures

• Main Authors: Yu-ChiHuang, 黃鈺祺
• Other Authors: Woei-Shyan Lee
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/54484924118990339258

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 101 === In this study, a spit-Hopkinson bar is utilized to study the effect of temperature and strain rate on impact response and microstructural characteristics of 6061-T6 aluminum alloy at different cryogenic temperatures of 0℃, -100℃and -196℃, under strain rates of 1000s-1, 3000s-1 and 5000s-1, respectively. The experimental results indicate that the mechanical properties are related to temperature and strain rate. At a constant temperature, flow stress and strain rate sensitivity all increase with the increasing strain rate, while the work hardening and thermal activation volume decreases. However, at a constant strain rate, flow stress and strain rate sensitivity decrease with increasing temperature, while the thermal activation volume increases. In addition, the observed impact deformation behavior of this alloy under current testing conditions can be described by the Zerilli-Armstrong equation. Optical microstructural observations reveal that the formation of adiabatic shear band and morphology of deformed grain of 6061-T6 aluminum alloy are strongly dependent on temperature and strain rate. Transmission electron microscopy (TEM) observations show that the dislocation density increases with increasing strain rate, but decreases with increasing temperature. Based on the experimental mechanical properties and microstructural characteristics, it is found that the correlation between the dislocation density and flow stress obeyed by the Bailey-Hirsch type relation. In addition, the flow stress, strain rate sensitivity and thermal activation volume are also related to the observed dislocation substructure.