MgB2 Superconducting Wire Swaging Deformation
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Solution Overview
Problem
The existing methods for manufacturing MgB2 superconducting wire materials, such as the Powder in Tube method, face challenges in achieving sufficient deformation and adhesion of precursor particles when using soft high-purity metals like copper or aluminum as outer layer materials, leading to reduced critical current density and thermal stability.
Innovation Solution
A method involving the synthesis of precursor particles by applying impact to magnesium and boron powders to create a dispersed structure, followed by filling a metal tube, wire forming through processing, and heat treatment with swaging to enhance deformation and adhesion, resulting in an MgB2 superconducting wire material with improved thermal stability and critical current characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the ex situ method is used to manufacture MgB2 wire material, then a relatively high sintering temperature (800 to 900°C) is required to bond MgB2 particles, but the magnetic flux pinning force is weakened
Solution Approach 1:
The invention changes the sintering temperature parameter from the conventional 800-900°C range to a lower range of 600-800°C, specifically 650-750°C, which maintains adequate particle bonding while preserving the magnetic flux pinning force by avoiding excessive grain growth that occurs at higher temperatures
2Reliability
If the in situ method is used to manufacture MgB2 wire material, then the MgB2 is generated at low-temperature heat treatment (700°C or lower) which is advantageous for magnetic flux pinning, but a large number of voids are generated and a sufficient superconducting current path cannot be obtained
Solution Approach 1:
The invention performs preliminary mechanical alloying and deformation processing before the final low-temperature sintering step. The precursor particles are pre-formed with adequate density and continuity through mechanical processing, which compensates for the void formation that occurs during low-temperature MgB2 generation, ensuring both magnetic flux pinning and current path continuity
3Stability of the object's composition
If mechanical milling method is used to synthesize precursor particles, then boron particles are dispersed in magnesium matrix, but the precursor particles are hard and do not deform sufficiently in metal sheath, and a sufficient adhesion between particles does not occur
Solution Approach 1:
The invention introduces dynamic deformation processing (swaging) after mechanical milling. The precursor particles undergo progressive deformation through repeated swaging operations, which transforms the hard, brittle particles into a more ductile state that can adhere properly to the metal sheath and to each other, while maintaining the beneficial dispersion structure created by mechanical milling
4Reliability
If soft high-purity metals like copper or aluminum are used as outer layer materials, then thermal stability is improved, but the precursor particles do not deform sufficiently and a sufficient adhesion does not occur
Solution Approach 1:
The invention applies dynamic swaging processing that creates sufficient deformation and adhesion even with soft outer layer materials. The progressive deformation through multiple swaging passes generates adequate mechanical interlocking and bonding between the precursor particles and the soft metal sheath, enabling the use of thermally stable soft metals like copper and aluminum without sacrificing adhesion
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 approach allows for the formation of MgB2 filaments with high continuity and critical current density, enabling stable energization and compact design in superconducting devices, even when using soft high-purity metals as outer layer materials.
Implementation Method 1
a pot is filled with magnesium powder and boron powder together with a ball, and is revolved at a high speed by a planetary mill device to collide the powder with the ball or an inner wall of the pot. By this process, precursor particles in which boron particles are dispersed in a magnesium matrix are synthesized.
Implementation Method 2
the wire material is formed in an order of drawing processing, cassette roller drawing, and swaging
Implementation Method 3
a heat treatment step of heat-treating the wire material to synthesize MgB2
Implementation Method 4
An advantage of a superconducting wire material is that a current can flow therethrough with zero resistance
Implementation Method 5
it has been pointed out that in the MgB2 a crystal grain boundary acts as a magnetic flux pinning center
Data Source
AI summary
The purpose of the present invention is to provide a method for causing sufficient deformation in precursor particles even when a soft high-purity metal is used for an outer layer material in mechanical milling, and manufacturing an MgB2 superconducting wire. A method for manufacturing an MgB2 superconducting wire in which an MgB2 filament is covered by an outer layer material, the method comprising: subjecting magnesium powder and boron powder to a shock that is insufficient for MgB2 to be clearly produced, and producing precursor particles in which boron particles are dispersed inside a magnesium matrix; filling a metal tub with the precursor particles; processing the metal tube filled with precursor particles to form a wire; and heat-treating the wire to synthesize the MgB2; wherein the method is characterized in that a portion of the wire-drawing step includes swaging.