TiAl Joining via Cu-Ni Insert Diffusion Bonding
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Solution Overview
Problem
Existing methods for joining TiAl intermetallic compounds require active pressure application, which is challenging for parts with complex shapes or large surface areas, and cannot ensure uniform pressure distribution, limiting their applicability.
Innovation Solution
A manufacturing method involving TiAl intermetallic compounds and insert materials with Ti, Cu, and Ni, where the insert materials are heated in a non-oxidizing atmosphere without active pressure, allowing for diffusion bonding and forming joining layers with acicular structures that provide high-temperature strength equivalent to the TiAl base material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If active pressure is applied to TiAl during diffusion bonding, then joining strength is improved, but applicability to complex shapes and large surface areas deteriorates
Solution Approach 1:
A Cu-based insert material is introduced as an intermediary between the TiAl base materials. This insert material has a lower melting point than TiAl, allowing it to melt and form a liquid phase that facilitates bonding without requiring high pressure. The insert material acts as a mediator that enables joining while accommodating complex geometries and large surface areas that would be difficult to bond under conventional high-pressure diffusion bonding conditions.
Solution Approach 2:
The joining process utilizes phase transition by heating the Cu-based insert material above its melting point to create a liquid phase. This liquid phase enables the insert material to flow and conform to the mating surfaces, ensuring intimate contact and effective bonding. After bonding, the liquid phase solidifies to form a strong joint. This phase transition approach eliminates the need for continuous high pressure application during the bonding process.
2Reliability
If heating temperature is increased above melting point of insert material, then diffusion bonding is enhanced, but risk of base material melting increases
Solution Approach 1:
The process exploits the phase transition of the Cu-based insert material by heating it above its melting point while maintaining the temperature below the melting point of the TiAl base materials. This creates a liquid phase in the insert material that enhances diffusion bonding, while the TiAl base materials remain in the solid state. The temperature window between the melting point of Cu (approximately 1085°C) and TiAl (approximately 1668°C) provides a safe operating range for the process.
Solution Approach 2:
The process parameters are carefully controlled to maintain heating temperature within a specific range: above the melting point of the Cu-based insert material to ensure liquid phase formation, but below the melting point of the TiAl base materials to prevent base material degradation. This parameter control strategy enables reliable diffusion bonding while avoiding the harmful effect of base material melting.
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 enables the creation of TiAl joined bodies with high-temperature strength without relying on shape or area considerations, and without the need for active pressure application, making it suitable for complex and large-scale structural components.
Implementation Method 1
diffusion bonding is performed by applying pressure to TiAl intermetallic compounds 101 while heating the TiAl intermetallic compounds 101 with heaters 102
Implementation Method 2
heating the plurality of members and the insert materials in a non-oxidizing atmosphere at a temperature above melting points of the insert materials and below melting points of the plurality of members
Implementation Method 3
an insert material of which a main component is a mixture of metal phases containing Al and Ti as major elements is positioned to a faying surface of two base materials of a TiAl intermetallic compound and are heated in a temperature range where the insert material become a TiAl intermetallic compound such that reaction synthesis joining is performed
Data Source
AI summary
A manufacturing method of a TiAl joined body includes: an arranging step and a heating step. The arranging step is a step of arranging a plurality of members which contains a TiAl intermetallic compound and insert materials which contain Ti as a major element, Cu and Ni such that each of the insert materials is inserted between two adjacent members of the plurality of members. The heating step is a step of heating the plurality of members and the insert materials in a non-oxidizing atmosphere at a temperature above melting points of the insert materials and below melting points of the plurality of members.