Effect of hydrogen solution on the Young’s modulus of Nickel

Abstract:
Nickel is known as a magnetostrictive material and is therefore widely used in actuators, sensors, vibration energy harvesting devices, etc. In the future, with the development of the hydrogen society, such as the widespread use of hydrogen vehicles, there is a need for magnetostrictive materials that can operate in a hydrogen environment. In this regard, nickel has the advantage that the heat of formation of nickel hydride is positive and no disproportionation reaction occurs when hydrogen is dissolved. Nevertheless, how the Young's modulus changes with hydrogen solidification has not been sufficiently discussed. Exploring how the Young's modulus of nickel changes is important from an energy efficiency perspective. Careful evaluation of the mechanical properties of metals containing hydrogen solutions is necessary to assess the mechanical properties of metals subjected to elastic deformation, since the Gorsky effect occurs in metals subjected to elastic deformation. In this study, we focused on the vibratory lead method as a non-destructive method of measuring Young's modulus and aimed to evaluate changes in the mechanical properties of pure nickel using the electrochemical hydrogen loading method. Young's modulus at low hydrogen concentration and high hydrogen concentration were compared under low and high current conditions, respectively. There was a clear change in both cases for the samples loaded with high current conditions, and in both cases, there was a significant decrease in the Young's modulus. This study suggests that diffuse hydrogen may have a significant effect on the mechanical properties of Ni, although it may include some of the internal frictional effects of solid hydrogen reported in a previous study. Also, the enhance local dislocations in the metal via dissolved hydrogen in the metal and its effect cannot be eliminated in the measurement of Young's modulus by the vibrational lead method.