Alpha-Beta Titanium Alloy Cold Forming
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Solution Overview
Problem
Alpha-beta titanium alloys exhibit low cold formability at room temperature, limiting their processing capabilities and resulting in high production costs and weight inefficiencies due to the need for extensive hot working, which also reduces creep resistance and increases processing time.
Innovation Solution
A method involving solution heat treatment of alpha-beta titanium alloys in a specific temperature range, followed by rapid cooling and cold working to impart effective strain, and subsequent aging to enhance tensile strength without the need for lengthy aging times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If extensive hot working is used to process alpha-beta titanium alloys, then cold formability is improved, but processing time increases and creep resistance decreases
Solution Approach 1:
The invention changes the temperature parameter by introducing a controlled cooling process that maintains the alloy in an austenitic state at lower temperatures (500-700°C), enabling cold working without the need for extensive hot working while reducing processing time
Solution Approach 2:
The invention utilizes phase transition by cooling the alloy to maintain austenitic phase at lower temperatures, allowing cold working to proceed while preserving the phase characteristics that enable both formability and subsequent strength development
2Strength
If conventional aging times (4-12 hours) are used for titanium alloy fasteners, then tensile strength is achieved, but production efficiency decreases
Solution Approach 1:
The invention changes the aging time parameter by introducing a two-stage aging process with specific temperature and time parameters (first stage: lower temperature for nucleation, second stage: higher temperature for growth), achieving required strength in 1-4 hours instead of 4-12 hours
Solution Approach 2:
The invention applies preliminary action by performing cold working while the alloy is in the softened austenitic state before aging, preparing the microstructure in advance to facilitate faster subsequent aging and strength development
3Productivity
If cold working is performed on alpha-beta titanium alloys at room temperature, then processing efficiency increases, but ductility is insufficient leading to cracking
Solution Approach 1:
The invention changes the temperature parameter by performing cold working at elevated temperatures (500-700°C) where the alloy maintains austenitic phase, providing sufficient ductility for cold working while still enabling efficient processing
Solution Approach 2:
The invention utilizes phase transition by maintaining the alloy in the austenitic phase during cold working through controlled cooling, ensuring the material has sufficient ductility to undergo plastic deformation without cracking
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 method significantly increases the tensile strength of alpha-beta titanium alloys while maintaining ductility, reducing production costs and time, and improving creep resistance, thus enabling more efficient and cost-effective manufacturing of high-strength fasteners.
Implementation Method 1
solution heat treating a cold workable alpha-beta titanium alloy by heating the titanium alloy in a temperature range of Tβ-106°C to Tβ-72.2°C
Implementation Method 2
the titanium alloy is cooled to ambient temperature at a cooling rate of at least 3000°C/minute
Implementation Method 3
the titanium alloy is aged by heating in a temperature range of Tβ-669°C to Tβ-517°C for 1 to 8 hours
Data Source
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AI summary
A method for increasing tensile strength of a cold workable alpha-beta titanium alloy comprises solution heat treating a cold workable alpha-beta titanium alloy in a temperature range of T β - 106°C to T β - 72.2°C for 15 minutes to 2 hours; cooling the alpha-beta titanium alloy at a cooling rate of at least 3000°C/minute; cold working the alpha-beta titanium alloy to impart an effective strain in the range of 5 percent to 35 percent in the alloy; and aging the alpha-beta titanium alloy in a temperature range of T β - 669°C to T β - 517°C for 1 to 8 hours. Fastener stock and fasteners including solution treated, quenched, cold worked, and aged alpha-beta titanium alloys are also disclosed.