Beta Titanium Fastener Microstructure for Defect-Free Thread Forming
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aeronautical fasteners made from titanium alloys face challenges in achieving a balance between low density and high mechanical strength, while maintaining ductility to avoid defects during manufacturing processes such as rolling or braking threads, which can degrade the mechanical properties of beta-metastable titanium alloys.
Innovation Solution
A fastening element made from a beta-metastable titanium alloy with a microstructure consisting of a beta phase matrix and alpha phase nodules, heat-treated within specific temperature ranges to control the distribution and size of alpha phase nodules, allowing for deformation without introducing defects, and processed to achieve a striated shape like threads or traction grooves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If beta-metastable titanium alloy is used to achieve high mechanical strength, then strength exceeds 1500 MPa, but ductility becomes very low making the material sensitive to manufacturing defects
Solution Approach 1:
The patent applies preliminary action by performing a first heat treatment before deformation operations to optimize the microstructure. The alloy is heated to a specific temperature range (800-950°C) and held for a predetermined time to achieve an optimal beta-phase microstructure with fine grain size, which provides both high strength and sufficient ductility for subsequent thread rolling or braking operations without generating defects
Solution Approach 2:
The patent applies parameter changes by precisely controlling heat treatment parameters (temperature, time, cooling rate) to transform the microstructure. The first heat treatment uses temperature T1 between 800-950°C for time t1, followed by a second heat treatment at temperature T2 between 450-550°C for time t2, which optimizes the beta-phase microstructure to enable defect-free deformation while maintaining high mechanical strength
2Strength
If heat treatment is applied to improve mechanical properties, then strength increases, but microstructural alterations occur that degrade properties
Solution Approach 1:
The patent applies parameter changes by defining precise heat treatment parameters: first heat treatment at temperature T1 between 800-950°C for time t1, then second heat treatment at temperature T2 between 450-550°C for time t2. These controlled parameter changes transform the microstructure to an optimal beta-phase structure with fine grain size, achieving high strength while maintaining microstructural stability and preventing degradation
3Weight of moving object
If TA6V alloy is used for fasteners with diameter exceeding 25 mm, then low density is maintained at 4.43 kg/dm3, but low conductivity limits heat treatment effectiveness reducing strength to less than 1100 MPa
Solution Approach 1:
The patent applies composite materials by using a multi-element alloy composition that combines titanium with aluminum (4-7%), vanadium (3-6%), molybdenum (3-6%), and chromium (2-4%). This composite alloying strategy creates a beta-metastable titanium alloy with improved thermal conductivity for effective heat treatment of large diameter fasteners, while maintaining low density and achieving high mechanical strength exceeding 1500 MPa
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 solution achieves high mechanical strength exceeding 1250 MPa with sufficient ductility, reducing the likelihood of defects during shaping and maintaining consistent mechanical properties across the fastener, enhancing its reliability and performance.
Implementation Method 1
Depending on the temperature, pure titanium can exhibit two crystallographic phases: the alpha (α) phase, hexagonal close-packed structure, or the beta (β) phase, body-centered cubic structure. Titanium alloys have the property of retaining more or less alpha or beta phase at room temperature
Implementation Method 2
The invention further relates to a method for manufacturing a fastener element described above, said method comprising the following steps: supplying a blank fastener made of beta-metastable titanium alloy, said alloy having a second microstructure consisting of a second beta phase matrix and alpha phase nodules distributed in said second matrix, said alloy having a temperature Tβ of transformation of the alpha phase into the beta phase; first heat treatment of the blank fastener, at a first temperature within a range [Tβ - 100 °C; Tβ - 10 °C], followed by cooling; then second heat treatment of the blank fastener, at a second temperature between 440 °C and 600 °C
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a fastener comprising a substantially right circular cylindrical surface arranged along an axis, said surface comprising a grooved shape selected from a thread, a tapping and a plurality of traction grooves, said fastener being made of a beta-metastable titanium alloy. The alloy has a microstructure (40) made up of a matrix (42) and alpha phase nodules (44) distributed in said matrix, the matrix being made up of beta phase and groups (46) of alpha phase lamellae (48) oriented in the same direction.