Cu-Al-Mn Shape-Memory Screw Threads via Form Rolling
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Solution Overview
Problem
Existing methods for joining Cu—Al—Mn-based shape-memory alloys, such as hot header riveting and shrink fitting, face challenges with productivity, material yield, and reliability due to the difficulty in forming threads and the need for specialized equipment, while cutting methods are time-consuming and prone to breakage.
Innovation Solution
A method involving form-rolling of Cu—Al—Mn-based alloys to create a screw portion with a surface layer of high hardness through compressive residual stress, converting the A2-type crystal structure to an L21-type structure via aging heat treatment, resulting in a screw portion with high resistance to fatigue and breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hot header riveting or shrink fitting is used for joining Cu-Al-Mn-based shape-memory alloys, then joint strength can be achieved, but productivity decreases and specialized equipment is required
Solution Approach 1:
The invention changes the material parameters by specifying precise compositional ranges (Al: 6-12 mass%, Mn: 8-18 mass%, Cu: balance) and microstructural parameters (martensitic phase with specific crystal structure) to enable the alloy to be form-rolled while maintaining shape-memory properties. This parameter optimization allows conventional form rolling equipment to process the material effectively, improving productivity without sacrificing joint strength
Solution Approach 2:
The invention replaces specialized joining equipment (hot header riveting machines, shrink fitting devices) with conventional form rolling equipment. By modifying the material properties through controlled composition and heat treatment, the patent enables standard mechanical forming processes to achieve joining, eliminating the need for specialized equipment and thereby improving productivity
2Manufacturing precision
If cutting methods are used to form screw portions, then threads can be created, but production time increases and breakage occurs
Solution Approach 1:
The invention replaces cutting-based thread formation with form rolling. By optimizing the alloy composition and creating a martensitic microstructure, the material gains sufficient ductility and strength to undergo plastic deformation through form rolling without breakage. This substitution eliminates time-consuming cutting operations while maintaining thread quality
Solution Approach 2:
The invention changes the material's mechanical parameters through controlled composition (specific Al and Mn content ranges) and heat treatment to achieve optimal ductility and strength. These parameter changes enable the material to withstand the plastic deformation of form rolling, preventing breakage and reducing production time compared to cutting methods
3Productivity
If form rolling is used to create screw portions, then productivity improves, but the material requires specific crystal structure and composition control
Solution Approach 1:
The invention establishes specific compositional parameters (Al: 6-12 mass%, Mn: 8-18 mass%, Cu: balance) and processing parameters (heat treatment temperatures, cooling rates) that transform the manufacturing process from complex and uncertain to controlled and repeatable. These defined parameters enable form rolling to be performed reliably, improving productivity while making the manufacturing process more manageable through standardization
Solution Approach 2:
The invention performs preliminary actions during material production by controlling composition and creating the martensitic microstructure before the joining operation. This preliminary preparation of the material's microstructure and properties enables subsequent form rolling to proceed smoothly with conventional equipment, offsetting the initial manufacturing complexity with streamlined downstream processing
4Reliability
If Ni-Ti-based shape-memory alloys are used, then shape-memory effect and superelasticity are achieved, but cost increases and workability decreases
Solution Approach 1:
The invention creates a copper-based composite alloy system (Cu-Al-Mn) that combines the desirable shape-memory properties of Ni-Ti alloys with the superior workability and lower cost of copper-based materials. The specific composition ranges and heat treatment processes create a martensitic microstructure that enables both shape-memory effect and ease of manufacturing, resolving the contradiction between reliability and ease of manufacture
Solution Approach 2:
The invention changes the base material parameters from Ni-Ti composition to Cu-Al-Mn composition, fundamentally altering the material's cost, density, and mechanical properties. Through controlled composition parameters and heat treatment parameters, the patent achieves shape-memory effect in a more workable and economical copper-based system, improving ease of manufacture while maintaining reliability
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 process enables the production of Cu—Al—Mn-based shape-memory alloy components with high working properties and resistance to fatigue and breaking, suitable for structural applications like seismic damping members, improving productivity and reliability.
Implementation Method 1
a surface layer with high hardness in a region with at least a certain depth from its surface due to the application of compressive residual stress
Implementation Method 2
subjecting heat-treatment so as to convert the A2-type crystal structure into an L21-type crystal structure
Data Source
AI summary
A formed body of Cu—Al—Mn-based shape-memory alloy may include a screw portion, wherein the screw portion is a form-rolled portion. A method for producing a formed body of Cu—Al—Mn-based shape-memory alloy may involve forming a screw portion having superelasticity by plastically working at least a portion of a material for the formed body with form-rolling in a state that a crystal structure is an A2-type structure and then, subjecting heat-treatment so as to convert the A2-type crystal structure into an L21-type crystal structure. The screw portion can be formed with good working property, and has excellent fatigue resistance and breaking resistance.