変位制御ミリインデンテーションに及ぼひずみ速度の影響

抄録

Recently, the strain rate effects of the indentation are frequently discussed with the nano-indentation. For the nano-indentation, undesirable effects such as grain boundaries and precipitates may influence test results, which may act as obstacles to understand strain rate effect. Effects of grain boundaries can be minimized by using milli-scale indenter. Additionally, it is difficult to analyze the strain rate effect of indentation, which is distributed inside a material. Thus, it is necessary to investigate strain rate effect without considering those distributions. In this study, in order to clarify the strain rate effect, the serration behavior of Al-Zn-Mg alloy was used, since serration behavior of this alloy would change depending on the strain rate. The purpose of this study is to investigate strain rate effect of Al-Zn-Mg alloy using displacement controlled milli-indentation. In experiment, displacements rates were changed twice from 1.0×10^-1 to 1.7×10^-3 m/s and from 1.7×10^-3 to 5.0×10^-4 m/s and each displacement changes were made after holding displacement for 150 s . It was found that loads were increased after the displacement holding. Additionally, severe serrations were observed when the displacement rate was changed to lower rates. It was surmised that strain rate effect of indentation can be analyzed using effective strain rate.