Titanium Alloy Sheet Composition for Low-Temperature Superplastic Forming
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Solution Overview
Problem
Current methods for manufacturing titanium alloy sheet materials for low-temperature superplastic forming are either costly or require special-purpose equipment, and existing compositions do not provide stable properties suitable for industrial production due to instability in intergranular sliding and grain growth issues.
Innovation Solution
A titanium alloy sheet material with a balanced chemical composition of 4.5-5.5Al, 4.5-5.5V, 0.1-1.0Mo, 0.8-1.5Fe, 0.1-0.5Cr, 0.1-0.5Ni, and 0.16-0.25O, with a molybdenum structural equivalent greater than 5 and aluminum structural equivalent less than 8, exhibiting superplastic properties at 775°C with grain sizes below 8 µm and an α/β phase ratio of 0.9 to 1.1, facilitating efficient intergranular sliding and stable deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermomechanical processing is used to produce ultrafine grains (2-1 μm) for low-temperature superplastic forming, then superplastic deformation capability is improved, but manufacturing cost and process complexity increase significantly
Solution Approach 1:
The invention changes the chemical composition parameters of the titanium alloy by adding specific amounts of Fe (0.8-1.5%) and Ni (0.1-0.5%) along with controlled Mo (0.1-1.0%), Cr (0.1-0.5%), and oxygen (0.16-0.25%). This compositional parameter change enables the material to achieve stable superplastic deformation at low temperatures without requiring complex ultrafine grain processing techniques, thus resolving the contradiction between deformation capability and process complexity
Solution Approach 2:
The invention creates a composite alloy system combining Ti-6Al-4V base alloy with additional Fe and Ni elements. This composite composition leverages the fast diffusion properties of Fe and Ni to enhance grain boundary sliding and superplasticity, achieving the desired deformation capability through material composition rather than complex processing
2Ease of manufacture
If low-temperature superplastic forming is implemented, then die cost is reduced and die life is increased, but existing alloy compositions exhibit instability in intergranular sliding and grain growth
Solution Approach 1:
The invention optimizes the chemical composition parameters within specific ranges: Fe (0.8-1.5%), Ni (0.1-0.5%), Mo (0.1-1.0%), Cr (0.1-0.5%), and O (0.16-0.25%). These parameter changes ensure stable intergranular sliding behavior during low-temperature superplastic forming while maintaining grain size control, thereby achieving both ease of manufacture and compositional stability
Solution Approach 2:
The invention introduces local quality enhancement by adding Fe and Ni elements that specifically target grain boundary regions. These elements concentrate at grain boundaries to enhance diffusion and sliding processes locally, providing stable deformation behavior without affecting the overall material structure, thus enabling reliable low-temperature forming
3Reliability
If alloying elements Fe and Ni are added to enhance fast diffusion and grain boundary sliding, then superplastic forming capability at low temperature is improved, but alloy composition complexity increases
Solution Approach 1:
The invention changes the alloy composition parameters by adding Fe (0.8-1.5%) and Ni (0.1-0.5%) to the Ti-6Al-4V base alloy. This parameter change introduces fast diffusion elements that enhance grain boundary sliding and superplasticity at low temperatures, achieving improved forming capability with controlled composition complexity
Solution Approach 2:
The invention uses Fe and Ni elements as substitutes for more complex processing techniques. Instead of employing complex thermomechanical processing to achieve ultrafine grains, the alloy composition is modified to inherently provide the necessary grain boundary characteristics, simplifying the overall manufacturing approach while maintaining reliability
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 cost-effective, stable low-temperature superplastic forming with improved mechanical properties and reduced grain growth, making it a viable alternative to Ti-6A1-4V alloy sheet products, suitable for aerospace and other structural applications.
Implementation Method 1
faster diffusion process which speeds up grain boundary sliding due to the content of, i.e., Fe and Ni in the alloy as fast diffusers
Implementation Method 2
titanium alloy sheets are normally able to undergo superplastic forming (deformation) within the temperature range of about 900 to 1010°C at the strain rate of about 3·10^-4
Data Source
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AI summary
Herein disclosed includes the manufacture of sheets from a titanium alloy having a chemical composition efficiently balanced with manufacturability based on known conventional manufacturing techniques for finished products exhibiting low temperature superplastic forming properties. The result is achieved by a sheet material for low temperature superplastic made of titanium alloy with the following content of element by % wt.: 4.5-5.5Al, 4.5-5.5V, 0.1-1.0Mo, 0.8-1.5Fe, 0.1-0.5Cr, 0.1-0.5Ni, 0.16-0.250, remainder is titanium and residual elements and having molybdenum structural equivalent [Mo]eqiv. > 5 and aluminum structural equivalent [Al]equiv. < 8; the equivalent values are calculated from the expressions: Moeqiv.=Mo+V/1.5+Cr×1.25+Fe×2.5×Ni/0.8 Aleqiv.=Al+O×10+Zr/6.