Superconducting MgB2 Wire Drawing Considering Anisotropic Hardening Behavior and Hydrostatic Effect

Abstract

Numerical modeling was conducted to investigate the deformation behavior of powder mixture during multi-pass drawing processes for multi-filamentary MgB2 wire. A modified Drucker-Prager Cap (DPC) model with an elliptical cap surface using the new material characterization method was developed to capture the anisotropic hardening behavior and hydrostatic effect of the powder mixture. A number of uniaxial die compaction, cold isostatic pressing, diametrical compression, and uniaxial compression tests were conducted using different powder densities to characterize the modified DPC model. A commercial finite element software ABAQUS with a user subroutine was used to simulate the drawing of the MgB2 wire. The density and area fraction of the powder mixture during the wire-drawing process were verified with experimental results. The difference in packing density at the inner and outer filaments of the MgB2 wire was successfully captured by simulation. In addition, the effect of the initial packing density on the superconducting properties of MgB2 wire was numerically studied. It is shown that the increase in the superconducting area, which results from a high initial packing density, should be more effective compared to the increase in the grain connectivity in enhancing the critical current properties for the MgB2 wire when the final packing density is saturated after a number of drawing processes. Graphic abstract