High-Entropy Alloy Composition for Broad-Range Magnetocaloric Effect
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Solution Overview
Problem
Existing high-entropy alloys (HEAs) do not exhibit a high magnetic entropy change over a sufficiently large temperature range, nor do they provide high magnetostriction, low magnetic anisotropy, high mechanical strength, and high ductility necessary for solid-state refrigeration and transduction devices.
Innovation Solution
Forming HEAs with specific compositions including Fe, Co, Ni, Cr, and optionally Mn, with alloying additions of Cu, Al, or Ga, and annealing them to achieve stable solid solutions with tailored magnetic properties, enabling a broad temperature range of magnetic entropy change and magnetostriction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If giant magnetocaloric materials with first-order magneto-structural phase transformation are used, then very large magnetic entropy change is achieved, but the temperature range is very narrow and transition temperature is often well below room temperature
Solution Approach 1:
The patent changes the magnetic transition order from first-order to second-order by modifying alloy composition and structure. This transforms the sharp, narrow temperature band transition into a broader, continuous transition that spans a larger temperature range while maintaining high magnetic entropy change, directly resolving the contradiction between peak entropy change and temperature range
Solution Approach 2:
The patent uses composite alloy systems combining multiple elements (Fe, Co, Ni, Cr, Mn, Al, Ga, Cu) to create high-entropy alloys with tailored magnetic properties. This composite approach enables simultaneous achievement of high magnetic entropy change and broad temperature range by leveraging synergistic effects of different elements
2Strength
If rare earth elements are used in magnetostrictive materials, then high magnetostriction is achieved, but the materials are expensive, brittle, and often pyrophoric
Solution Approach 1:
The patent replaces expensive rare earth elements with abundant, inexpensive transition metals (Fe, Co, Ni, Cr, Mn) to create cost-effective magnetostrictive materials. This substitution maintains functional performance while eliminating the drawbacks of rare earth-based materials including high cost, brittleness, and pyrophoricity
Solution Approach 2:
The patent modifies the crystal structure and magnetic properties by adjusting alloy composition ratios and heat treatment parameters. This enables achievement of high magnetostriction in rare-earth-free alloys through controlled changes in microstructure and magnetic phase characteristics
3Temperature
If Fe is added to rare earth-based magnetostrictive materials to operate at room temperature, then operating temperature is improved, but magnetic strain is reduced substantially
Solution Approach 1:
The patent creates composite alloy systems where Fe is combined with Co, Ni, Cr, Mn, and other elements in specific ratios. This composite approach compensates for the reduction in magnetic strain caused by Fe addition, as the synergistic interaction between elements restores and enhances magnetostrictive properties while maintaining room temperature operation
Solution Approach 2:
The patent develops multi-functional high-entropy alloys that simultaneously provide magnetostriction, magnetocaloric effect, and good mechanical properties. This universal material design allows a single alloy system to perform multiple functions that were previously required separate rare earth-based materials
4Ease of manufacture
If conventional alloys with one major element and several minor elements are used, then manufacturing is simplified, but magnetic properties and mechanical strength are limited
Solution Approach 1:
The patent changes the fundamental composition parameter from conventional single-major-element alloys to equiatomic or near-equiatomic multi-element high-entropy alloys. This parameter change creates severe lattice distortion and sluggish diffusion that simultaneously enhance both mechanical strength and magnetic properties, resolving the contradiction between manufacturing simplicity and performance
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
The HEAs demonstrate a high magnetic entropy change over a large temperature range, enhancing solid-state refrigeration efficiency and reducing the need for environmentally harmful refrigerants, while also exhibiting notable magnetostriction and mechanical properties suitable for energy harvesting applications.
Implementation Method 1
High-entropy alloys (HEAs), methods for making HEAs, and uses thereof High-entropy alloys (HEAs) that exhibit a high magnetic entropy change over a large temperature range
Implementation Method 2
The invention also provides HEAs that exhibit significant magnetostriction at room temperature
Data Source
AI summary
High entropy alloys (HEAs) are provided, which exhibit a high magnetic entropy change over a large temperature range, as well as methods for making HEAs. The invention also provides HEAs that exhibit notable magnetostriction at room temperature, and alloying methods for producing them. The materials and methods of the invention may be used, for example, in solid-state refrigeration apparatus and methods, as well as in transduction devices and energy harvesting applications.