Microstructure Dependence of Mechanical Property of Commercial MgB₂ Composite Wires

抄録

It is known that four kinds of MgB₂ composite wires have been commercialized. The present study aims to compare the difference of microstructure dependence of mechanical property of those wires. The volume fraction of MgB₂ filaments in the wire was designed in the range between 0.1 and 0.19. The voids existing in MgB₂ filaments distributed in the scale smaller than a few ten micron meter. The tensile test was carried out at room temperature. Young’s modulus, 0.2 % proof stress and strain were determined. The calculated Young’s modulus was larger than the observed one for all four different wires. This discrepancy was attributed to the poor sintering of MgB₂ filaments as the existence of voids. This situation was proved by the numerically calculated results. A way to realize the higher ductility MgB₂ wire was proposed. The proof stress and strain shall be enhanced by replacing to other constituent metallic element with high thermal expansion coefficient and high Young’s modulus. The further requirement is to densify MgB₂ polycrystalline filaments for reducing the void fraction.