MgB2 Wire Precursor Composite Sheath for Uniform Deformation
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Solution Overview
Problem
During the PIT in-situ method for preparing MgB2 multi-core wires, non-uniform deformation and breakage of the barrier metal layer occur due to uneven stress distribution during the wire drawing process, leading to discontinuity of MgB2 filaments and reduced critical current density (Jc).
Innovation Solution
A precursor structure is designed with a soft Cu- and Fe-based metal at the center and a mixed powder element with a barrier metal sheath material surrounding it, where the core material and outer shell layer are harder than the sheath material, ensuring uniform deformation and preventing reaction between Mg and Cu.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier metal layer is used to prevent reaction between Cu and Mg, then reaction prevention is improved, but the layer breaks during wire drawing process due to non-uniform deformation
Solution Approach 1:
The patent employs a composite sheath structure consisting of an inner barrier metal layer (Nb or Ta) and an outer Cu layer. This composite design allows the barrier metal to prevent Mg-Cu reaction while the Cu layer provides mechanical strength and ductility during wire drawing, preventing the barrier layer from breaking.
Solution Approach 2:
The sheath material has non-uniform composition with different layers serving different functions: the inner barrier metal layer provides chemical stability and reaction prevention, while the outer Cu layer provides mechanical flexibility. This local differentiation of material properties resolves the contradiction between reaction prevention and mechanical integrity.
2Stability of the object's composition
If Cu stabilizing material is used, then thermal stability is improved, but MgB2 synthesis is destabilized due to reaction between Cu and Mg at high temperature
Solution Approach 1:
The barrier metal layer (Nb or Ta) acts as an intermediary between the Cu stabilizing material and Mg powders. It physically separates Cu and Mg, preventing direct reaction during high-temperature synthesis while allowing Cu to provide thermal stability to the superconducting wire.
Solution Approach 2:
The double-layer sheath structure combines Cu for thermal stability with a barrier metal layer for chemical compatibility. This composite material approach allows both functions to coexist: Cu provides thermal stability while the barrier layer prevents harmful reactions during synthesis.
3Reliability
If the sheath material is made hard to prevent reaction, then reaction prevention is improved, but non-uniform deformation occurs during wire drawing process
Solution Approach 1:
The sheath is constructed as a composite with an inner barrier metal layer for reaction prevention and an outer Cu layer for mechanical ductility. The Cu layer's softness compensates for the hardness of the barrier layer, enabling uniform deformation during wire drawing while maintaining reaction prevention capabilities.
Solution Approach 2:
Different regions of the sheath have different mechanical properties: the inner barrier layer is hard and chemically stable, while the outer Cu layer is soft and ductile. This spatial differentiation of material properties allows the sheath to both prevent reactions and deform uniformly during manufacturing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration results in a MgB2 multi-core wire with a favorable sectional shape and suppressed filament disorder, maintaining high critical current density and thermal stability.
Implementation Method 1
it is necessary to use a metal such as Nb and Fe having a barrier function for preventing reaction between Cu and Mg as a sheath material of the mixed powder elements
Implementation Method 2
A plurality of mixed powder elements is bundled and incorporated into a metal pipe, the pipe incorporated with the elements passes through a die by using a draw plier to repeat the process, and a sectional area is gradually reduced
Implementation Method 3
A wire prepared by the in-situ method of synthesizing MgB2 after wire drawing has a high degree of coupling of MgB2 phase
Data Source
AI summary
Proposed is a novel embedded structure for suppressing a disturbance in the cross sectional shape and a non-uniform deformation of a metal member arising in a precursor when producing an MgB2 multi-core wire material by a surface reduction process. This superconductive multi-core wire material precursor is characterized by having: soft Cu and Fe pure metals disposed in the center; mixed powder elements, each comprising as a sheath material a metal such as Fe or Nb having a barrier effect preventing a reaction between Mg and Cu, the mixed powder elements being disposed in a form that surrounds the periphery of the soft metal serving as the central material; and disposed around these, an outer shell layer produced from a harder metal than the central material and the sheath material.