Niobium-Titanium Hairspring Two-Phase Microstructure
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Solution Overview
Problem
The production of watch springs faces challenges in achieving a high elastic limit, low modulus of elasticity, ease of production, excellent fatigue resistance, and thermal compensation, while maintaining mechanical strength and avoiding local fragility and complexity in composition and arrangement.
Innovation Solution
A binary niobium-titanium alloy with a two-phase microstructure, comprising centered cubic beta niobium and compact hexagonal alpha titanium, is developed, with a titanium content between 45.0% and 48.0% by mass, and a method involving coupled deformation-precipitation heat treatment to achieve an elastic limit greater than 1000 MPa and a modulus of elasticity between 60 GPa and 80 GPa, facilitating the production of spiral springs with improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high elastic limit is achieved through material improvement, then mechanical strength is improved, but the modulus of elasticity increases making the spring stiffer and harder to produce
Solution Approach 1:
The patent applies parameter changes by precisely controlling the titanium content (45-48 mass%) and applying specific heat treatment parameters (temperature and time) to transform the microstructure. This resolves the contradiction by achieving high elastic limit through controlled phase transformation rather than simply increasing material strength, thereby maintaining manufacturability
Solution Approach 2:
The patent creates a composite microstructure consisting of two phases: martensitic phase (providing high elastic limit) and retained austenitic phase (providing ductility and lower stiffness). This composite structure at the micro level resolves the contradiction by combining the benefits of both phases - high strength from martensite and ease of deformation from retained austenite
2Ease of manufacture
If the modulus of elasticity is reduced for easier production, then ease of production is improved, but the mechanical strength and elastic limit decrease
Solution Approach 1:
The patent creates a composite microstructure consisting of two phases: martensitic phase (providing high elastic limit) and retained austenitic phase (providing ductility and lower stiffness). This composite structure at the micro level resolves the contradiction by combining the benefits of both phases - high strength from martensite and ease of deformation from retained austenite
Solution Approach 2:
The patent applies local quality by creating different phases in different regions of the microstructure. The martensitic regions provide local strength while the retained austenitic regions provide local ductility and ease of deformation. This local differentiation resolves the contradiction between strength and ease of production
3Reliability
If thermal compensation is achieved through alloy selection, then chronometric performance is improved, but the composition complexity and local fragility increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the titanium content within a narrow range (45-48 mass%) and applying specific heat treatment parameters (temperature and time) to transform the microstructure. This resolves the contradiction by achieving high elastic limit through controlled phase transformation rather than simply increasing material strength, thereby maintaining manufacturability
Solution Approach 2:
The patent creates a composite microstructure consisting of two phases: martensitic phase (providing high elastic limit) and retained austenitic phase (providing ductility and lower stiffness). This composite structure at the micro level resolves the contradiction by combining the benefits of both phases - high strength from martensite and ease of deformation from retained austenite
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 niobium-titanium alloy achieves a high elastic limit and low modulus of elasticity, ensuring robustness and ease of production, while the two-phase microstructure helps in maintaining chronometric performance by adjusting the thermoelastic coefficient to near zero, suitable for both barrel and hairspring applications.
Implementation Method 1
The material is in the form of an alloy in binary type comprising niobium and titanium... with a two-phase microstructure comprising centered cubic beta niobium and compact hexagonal alpha titanium
Implementation Method 2
coupled deformation-precipitation heat treatment to achieve an elastic limit greater than 1000 MPa
Data Source
Figure 1~3
AI summary
Bi-phase spiral watch spring, made of niobium and titanium alloy, and manufacturing process of this spring, with: - preparation of a binary alloy comprising niobium and titanium, with: - niobium: balance at 100%; - titanium between 45.0% and 48.0% by mass of the total, - traces of components among O, H, C, Fe, Ta, N, Ni, Si, Cu, Al, between 0 and 1600 ppm of the total by mass individually, with cumulative less than 0.3% by mass; - application of alternating deformations to heat treatments to obtain a two-phase microstructure comprising a solid solution of niobium with titanium in the β phase and a solid solution of niobium with titanium in the a phase, the titanium content in the α phase being greater than 10% by volume, with a yield strength greater than 1000 MPa, and a modulus of elasticity less than 80 GPa; - drawing to obtain calenderable wire; - calendering or ring forming to form a barrel spring, in a treble clef before its first winding, or stretching to form a spiral spring.