Titanium Alloy Fastener Microstructure for Defect-Free Forming
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Solution Overview
Problem
Aeronautical fasteners made from beta-metastable titanium alloys face challenges in achieving high mechanical strength and low density while maintaining ductility, as they are prone to defects during manufacturing processes like rolling or crimping, which degrade their mechanical properties.
Innovation Solution
A fastener made from a beta-metastable titanium alloy with a specific microstructure comprising a beta-phase matrix and alpha-phase nodules, subjected to a controlled heat treatment process to achieve a tensile strength above 1250 MPa and ductility greater than 10%, with deformation operations conducted at temperatures below 620°C to prevent microstructure alteration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If beta-metastable titanium alloy is used to achieve high mechanical strength (up to 1500 MPa) and low density (4.7 kg/dm³), then the mechanical strength and weight performance are improved, but the low ductility makes the material very sensitive to manufacturing processes, causing defects like cracks or shear bands during rolling or crimping operations
Solution Approach 1:
The invention changes the temperature parameter during deformation operations, specifically performing rolling or crimping at temperatures between 500°C and 600°C. This temperature range increases the ductility of the beta-metastable titanium alloy, allowing deformation operations to be performed without creating cracks or shear bands, while maintaining the high mechanical strength properties
Solution Approach 2:
The invention applies a preliminary heat treatment before deformation operations to prepare the material in the appropriate state. By heating the material to the optimal temperature range before rolling or crimping, the material's ductility is enhanced in advance, preventing defects during the subsequent deformation process
2Ease of manufacture
If heating is applied during deformation operations to improve ductility, then the ease of manufacture is improved, but heating can lead to alterations in microstructure that degrade the mechanical properties of the material
Solution Approach 1:
The invention precisely controls the temperature parameter during heating, limiting it to the range of 500°C to 600°C. This controlled heating provides sufficient ductility for deformation operations while staying below the threshold that would cause detrimental microstructure alterations, thus maintaining high mechanical strength
Solution Approach 2:
The invention dynamically adjusts the temperature during the manufacturing process, heating the material only during deformation operations to the specific range of 500°C-600°C, and then allowing it to cool. This dynamic temperature control enables ductility when needed while preserving microstructure and strength when not deforming
3Weight of moving object
If conventional titanium alloy TA6V is used, then the low density (4.43 kg/dm³) is maintained, but the intrinsic mechanical strength is limited to about 1250 MPa and heat treatment efficiency is reduced for fasteners with diameter of about 25 mm
Solution Approach 1:
The invention uses a composite microstructure consisting of alpha-phase nodules distributed in a beta-phase matrix. This composite structure at the microstructural level provides both the low density characteristic of titanium alloys and the enhanced mechanical strength properties, achieving tensile strengths exceeding 1250 MPa while maintaining density around 4.7 kg/dm³
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 enables the production of fasteners with high mechanical strength and low density, minimizing defects and maintaining reproducible mechanical properties, thus addressing the limitations of existing titanium alloys like TA6V and Beta C alloys.
Implementation Method 1
pure titanium can have two crystallographic phases: alpha phase (α), compact hexagonal structure, or beta phase (β), centered cubic structure
Implementation Method 2
first heat treatment of the fastener blank, at a first temperature in a range [Tβ-100° C.; Tβ-10° C.], followed by cooling; then second heat treatment of the fastener blank, at a second temperature of between 440° C. and 600° C.
Data Source
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.