Hot-Forged TiAl Alloy Phase Control for Ductility and Strength
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Solution Overview
Problem
TiAl-based hot-forged alloys face challenges in achieving excellent hot forgeability, ductility at room temperature, and strength due to the retention of a certain amount of β phase, which degrades room temperature ductility and strength.
Innovation Solution
A TiAl-based alloy with a composition of Al: 41 to 43 at%, Fe: 0 to 2.5 at%, Ni: 0 to 2.5 at%, Mo: 0 to 2.0 at%, W: 0 to 2.0 at%, Cr: 0 to 4.5 at%, Mn: 0 to 5.5 at%, V: 0 to 10 at%, Nb: 0 to 10 at%, C: 0.3 to 0.7 at%, and the remainder Ti and inevitable impurities, with a microstructure consisting of a γ phase of 5 to 30%, a β phase of 0.5 to 5%, and a lamellar structure after heat treatment, promoting γ phase precipitation from β phase to optimize γ and β phase ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a certain amount of β phase is retained to improve hot forgeability, then hot forgeability is enhanced, but ductility at room temperature deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the alloy composition parameters (Al: 41-43 at%, Fe: 0-2.5 at%, Ni: 0-2.5 at%, Mo: 0-2.0 at%, W: 0-2.0 at%, Cr: 0-4.5 at%, Mn: 0-5.5 at%, V: 0-10 at%, Nb: 0-10 at%, C: 0.3-0.7 at%) and heat treatment parameters (holding temperature: 1200-1250°C, holding time: 0.5-5 h, cooling rate: 1-10°C/min) to optimize the phase distribution. This enables achieving both excellent hot forgeability and high ductility at room temperature by controlling the area fractions of γ phase (5-30%) and β phase (0.5-5%) in the microstructure.
Solution Approach 2:
The patent utilizes phase transitions by performing heat treatment in the α phase region after hot forging. The controlled cooling process transforms the microstructure to contain γ phase (5-30 area %) and β phase (0.5-5 area %) with a lamellar structure, optimizing the balance between hot forgeability and room temperature ductility through phase transformation control.
2Strength
If a completely lamellar structure with no β phase is obtained to enhance creep strength, then creep strength is improved, but hot forgeability deteriorates
Solution Approach 1:
The patent changes the parameter of β phase content from zero (completely lamellar structure) to a controlled range (0.5-5 area %) through optimized composition parameters and heat treatment parameters. This allows the material to maintain excellent creep strength while achieving superior hot forgeability, as the small amount of β phase provides deformation capability during hot working.
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 provides a TiAl-based alloy with enhanced hot forgeability and ductility at room temperature while maintaining strength, by controlling the area rates of γ, β, and lamellar structures through specific heat treatment conditions.
Implementation Method 1
an alloy element parameter P obtained by Expression (1) is in a composition range of 1.1 to 1.9, and the TiAl-based alloy has a microstructure consisting of a γ phase of 5 to 30 area %, a β phase of 0.5 to 5 area %, and a lamellar structure occupying a remaining part in a final state after heat treatment performed after hot forging
Data Source
AI summary
The present invention provides a TiAl-based alloy, including: Al: 41 to 43 at %; Fe: 0 to 2.5 at %; Ni: 0 to 2.5 at %; Mo: 0 to 2.0 at %; W: 0 to 2.0 at %; Cr: 0 to 4.5 at %; Mn: 0 to 5.5 at %; V: 0 to 10 at %; Nb: 0 to 10 at %; C: 0.3 to 0.7 at %; and a remainder consisting of Ti and inevitable impurities, in which an alloy element parameter “P=(41.5−Al)/3+Fe+Ni+Mo+W+0.5 Cr+0.4 Mn+0.2 V+0.2 Nb—C” is in a composition range of 1.1 to 1.9, and the TiAl-based alloy has a microstructure consisting of a γ phase of 5 to 30 area %, a β phase of 0.5 to 5 area %, and a lamellar structure occupying a remaining part.