Copper-Based Shape-Memory Alloy with B2 Precipitates for Fatigue Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional copper-based shape-memory alloys suffer from poor fatigue resistance and fracture resistance when deformed repeatedly, particularly under stress-specific strains, due to issues with crystal structure order and workability, limiting their practical applications.
Innovation Solution
A copper-based alloy with a multiphase structure including a B2-type precipitation phase dispersed in a β phase matrix, achieved through a specific production method involving melting, casting, hot working, intermediate annealing, and quenching, which enhances the degree of order and reduces residual strain accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the degree of order of the crystal structure is increased to improve fatigue resistance and fracture resistance, then the shape memory effect and superelasticity are enhanced, but the workability and cold workability are degraded
Solution Approach 1:
The patent applies parameter changes by precisely controlling the alloy composition parameters (Cu-17.0at% Al-10.0at% Mn-2.0at% Ni) and heat treatment parameters (solution treatment at 973-1173K, quenching, aging at 473-673K) to achieve the optimal balance between degree of order and workability. This allows the material to have sufficient fatigue resistance while maintaining adequate workability for practical applications.
Solution Approach 2:
The patent creates a composite microstructure consisting of an ordered β phase matrix with precipitated phases (such as NiAl intermetallic compounds). This composite structure at the microscale provides both the high degree of order needed for fatigue resistance and the appropriate mechanical properties for workability, resolving the contradiction between reliability and ease of manufacture.
2Stability of the object's composition
If special production methods such as quenching solidification or Czochralski method are used to achieve high degree of order, then the crystal structure order is improved, but the flexibility of shapes that can be produced is lowered
Solution Approach 1:
The patent applies preliminary action by performing solution treatment and quenching early in the processing sequence to establish the desired crystal structure order (L21-type or B2-type) in the matrix. Subsequent aging treatments then precipitate strengthening phases. This sequence allows the base crystal structure to be optimized first, followed by microstructural refinement, enabling both high order and shape flexibility.
Solution Approach 2:
The patent segments the heat treatment process into distinct stages: solution treatment to dissolve alloying elements, quenching to trap a high-temperature crystal structure, and aging to precipitate intermetallic phases. This segmentation allows independent optimization of crystal structure order and microstructural features, achieving high reliability while maintaining adaptability for various shapes.
3Quantity of substance
If conventional copper-based alloy is used to reduce cost, then the material cost is reduced, but the cold workability and target levels of shape memory effect are not reached
Solution Approach 1:
The patent changes the compositional parameters by adding a small amount of Ni (2.0at%) to the Cu-Al-Mn system, and precisely controlling the Al and Mn content. This compositional parameter change enables the material to achieve the desired degree of order and shape memory characteristics while maintaining cost-effectiveness. The heat treatment parameters are also optimized to achieve the target microstructure with conventional processing.
Solution Approach 2:
The patent applies local quality by creating a specific microstructure where NiAl precipitates are distributed within the ordered β phase matrix. This localized precipitation pattern provides the necessary strengthening and shape memory effect in the critical regions, while the overall composition remains cost-effective. The local microstructural quality compensates for the modest alloy composition, achieving target performance at reasonable cost.
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 alloy exhibits excellent fatigue resistance and fracture resistance, maintaining performance even after repeated deformation cycles, making it suitable for various applications including vibration damping and self-restoration materials.
Implementation Method 1
the shape-memory alloy shows the remarkable shape memory effect and superelasticity accompanied with the reverse transformation of thermoelastic martensitic transformation
Implementation Method 2
a step (step 10) of performing quenching after a step (step 9) of performing heating to a temperature range in the state of the (α+β) phase is changed to the state of the β single phase
Data Source
AI summary
A copper-based alloy material including a multiphase structure containing a matrix of a β phase and a precipitation phase of a B2-type crystal structure dispersed in the matrix, where the copper-based alloy material includes a composition containing 8.6 to 12.6% by mass of Al, 2.9 to 8.9% by mass of Mn, 3.2 to 10.0% by mass of Ni, and Cu.