Alpha-Beta Titanium Alloy Wire Grain Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional titanium alloys face challenges in achieving stable high fatigue strength due to issues such as coarse grain formation, notch sensitivity, and reduced ductility, particularly when attempting to create an equiaxed crystal structure in α+β type titanium alloys.
Innovation Solution
The development of an α+β type titanium alloy wire with specific chemical compositions and a manufacturing method involving cold or warm working within a temperature range of 0°C to 500°C, followed by heat treatment, to achieve a fine equiaxed crystal structure with controlled grain sizes and orientations, reducing the formation of coarse grains and internal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If hot working is performed in the α+β two-phase high-temperature region to obtain equiaxed crystal structure, then the equiaxed crystal structure is formed, but coarse proeutectoid α phase is likely to form and grain size becomes coarse leading to deteriorated fatigue properties
Solution Approach 1:
The patent applies parameter changes by precisely controlling working temperature within the α+β two-phase region (specifically 950-1050°C) and controlling the working amount to be 5-50% reduction in area. It also controls the cooling rate after working to be 10-100°C/s. These parameter optimizations prevent coarse proeutectoid α phase formation while maintaining equiaxed crystal structure, resolving the contradiction between forming equiaxed structure and controlling grain size precision.
2Productivity
If working is performed at high strain rate to reduce working time and cost, then productivity is improved, but working heat generation heats titanium to β region forming acicular structure
Solution Approach 1:
The patent applies preliminary anti-action by performing working in the α+β two-phase region where the material has adequate ductility and workability, rather than in the β single-phase region. This preliminary choice of working region prevents the formation of acicular structure that would occur if heating to β region happened during high-strain-rate working. The controlled strain rate keeps working heat generation below the threshold that would cause unwanted phase transformation.
3Shape
If working is performed at low strain rate to prevent heating to β region, then crystal structure is maintained, but working time is increased causing cost increase
Solution Approach 1:
The patent optimizes the strain rate parameter to a specific range (0.01-10 s⁻¹) that balances two opposing requirements: it is low enough to prevent excessive working heat generation that would heat the material to the β region, but high enough to maintain acceptable productivity. Combined with precise temperature control (950-1050°C) and controlled working amount (5-50% reduction in area), this parameter optimization achieves both structure maintenance and reasonable working time.
4Ease of manufacture
If hot working is performed to improve workability, then workability is improved, but coarse grain structure is formed leading to reduced fatigue strength
Solution Approach 1:
The patent applies parameter changes by optimizing the working temperature to 950-1050°C within the α+β two-phase region, controlling the working amount to 5-50% reduction in area, and controlling the cooling rate to 10-100°C/s. These optimized parameters enable adequate workability during processing while preventing coarse grain formation and proeutectoid α phase coarsening, thereby maintaining high fatigue strength in the final product.
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
This approach results in an α+β type titanium alloy wire with enhanced fatigue properties, including improved resistance to crack initiation and facet formation, leading to higher fatigue strength and stability.
Implementation Method 1
transformation occurs from a β phase being a high-temperature stable phase into an α phase
Implementation Method 2
working heat generation is likely to occur in titanium
Data Source
AI summary
An α+β type titanium alloy wire contains, in mass %, Al: 4.50 to 6.75%, Si: 0 to 0.50%, C: 0.080% or less, N: 0.050% or less, H: 0.016% or less, O: 0.25% or less, Mo: 0 to 5.5%, V: 0 to 4.50%, Nb: 0 to 3.0%, Fe: 0 to 2.10%, Cr: 0 to less than 0.25%, Ni: 0 to less than 0.15%, Mn: 0 to less than 0.25%, and the balance being Ti and impurities, the contents of Al, Mo, V, Nb, Fe, Cr, Ni, and Mn satisfying an equation, in which an average aspect ratio of an α crystal grain is 1.0 to 3.0, a maximum crystal grain diameter of the α crystal grain is 30.0 μm or less, an average crystal grain diameter of the α crystal grain is 1.0 to 15.0 μm.