Metastable Beta Titanium Timepiece Springs for Magnetic Stability
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Solution Overview
Problem
Current timepiece spring materials, such as nickel-iron and cobalt-nickel-chrome alloys, exhibit high sensitivity to magnetic fields and temperature variations, leading to torque and natural frequency drift, and have limitations in miniaturization and mechanical properties.
Innovation Solution
A metastable β titanium alloy with a specific composition and crystallographic structure, comprising a mixture of austenitic and alpha phases with omega-phase precipitates, offering super-elastic properties, low elastic modulus, and negligible magnetic susceptibility, is used to produce timepiece springs through a method involving work hardening and heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nickel-iron based alloys (Elinvar) are used for hairsprings, then the alloy provides good elastic properties, but the alloy exhibits high sensitivity to magnetic fields causing torque and natural frequency drift
Solution Approach 1:
The patent changes the material composition parameters by using titanium as the base metal instead of nickel-iron, and carefully controlling the percentages of alloying elements (Nb: 24-45%, Zr: 0-20%, Ta: 0-10%, Si: 0-1.5%) to achieve the desired magnetic and elastic properties. This parameter change eliminates magnetic sensitivity while maintaining elastic performance
Solution Approach 2:
The patent creates a composite material system with a specific microstructure consisting of a beta-phase matrix with alpha-phase precipitates and controlled omega-phase content. This composite microstructure combines the non-magnetic properties of titanium-based alloys with the elastic characteristics needed for hairsprings, resolving the contradiction between elastic performance and magnetic sensitivity
2Strength
If cobalt-nickel-chrome based alloys (Nivaflex) are used for mainsprings, then the alloy provides high elastic modulus, but the working reserve is moderate
Solution Approach 1:
The patent changes the material parameters by using a titanium-based alloy with specific composition ranges (Nb: 24-45%, Zr: 0-20%, Ta: 0-10%) that enables both high elastic modulus and increased working reserve. The controlled composition allows the material to store more elastic energy while maintaining the necessary stiffness for mainspring function
Solution Approach 2:
The patent utilizes phase transitions and microstructural transformations, specifically controlling the presence of alpha-phase precipitates and omega-phase in the beta-phase matrix. This phase control enables the material to achieve optimal balance between elastic modulus and working reserve, allowing greater energy storage capacity while maintaining structural integrity
3Ease of manufacture
If standard forming methods are used for titanium-based alloys, then the material can be processed, but miniaturization is extremely difficult and limited with reduction in mechanical properties
Solution Approach 1:
The patent changes the material parameters by optimizing the alloy composition (Nb: 24-45%, Zr: 0-20%, Ta: 0-10%, Si: 0-1.5%) to improve formability and ductility. This composition optimization allows the titanium-based alloy to undergo miniaturization processes without significant loss of mechanical properties, enabling precise manufacturing of small-scale springs
Solution Approach 2:
The patent employs a composite microstructure with beta-phase matrix, alpha-phase precipitates, and controlled omega-phase content. This composite structure provides a balance between strength and ductility, allowing the material to be miniaturized while maintaining mechanical properties. The multi-phase structure enables plastic deformation during forming without catastrophic failure
4Volume of moving object
If timepiece springs are miniaturized, then the size is reduced, but the mechanical properties and surface quality deteriorate
Solution Approach 1:
The patent changes the material composition parameters to include specific ranges of Nb (24-45%), Zr (0-20%), Ta (0-10%), and Si (0-1.5%), which improve the material's ductility and surface integrity during miniaturization. These parameter changes allow the spring to be scaled down while maintaining surface quality and mechanical properties
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 metastable β titanium alloy results in timepiece springs with constant torque and natural frequency, improved mechanical properties, and enhanced energy storage capacity, while maintaining stability across varying temperatures and magnetic fields.
Implementation Method 1
a crystallographic structure comprising: a mixture of austenitic phase and alpha phase, and a presence of omega-phase precipitates
Implementation Method 2
offering super-elastic properties
Implementation Method 3
A method for implementing a timepiece spring produced based on a metastable β titanium alloy
Implementation Method 4
A method for implementing a timepiece spring produced based on a metastable β titanium alloy
Data Source
AI summary
A metastable β titanium alloy is provided, which includes, by weight percent, between 24 and 45% niobium, between 0 and 20% zirconium, between 0 and 10% tantalum and/or between 0 and 1.5% silicon and/or less than 2% oxygen, said alloy having a crystallographic structure containing:a mix of austenitic phase and alpha phase; anda presence of omega phase precipitates the volume fraction of which is less than 10%. Also provided is a timepiece spring made from such an alloy and a method for producing such a spring.