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Microstructure Refinement of a Transformation-Induced Plasticity High-Entropy Alloy
Hailong Yi1, Daixiu Wei2, Renyi Xie1
1State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China.
Materials (Basel, Switzerland)
|April 3, 2021
Summary
High-entropy alloys (HEAs) exhibit excellent properties. This study reveals how hot compression influences the microstructure of a transformation-induced plasticity HEA, detailing grain refinement via discontinuous dynamic recrystallization for optimized thermomechanical processing.
Area of Science:
- Materials Science
- Metallurgy
- Physical Metallurgy
Background:
- High-entropy alloys (HEAs) are recognized for their unique structures and mechanical properties.
- Previous research highlighted novel Co-rich twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) HEAs with superior room-temperature tensile properties.
- The hot deformation behavior of these advanced HEAs remained largely unexplored.
Purpose of the Study:
- To investigate the hot deformation behavior, specifically dynamic recrystallization (DRX) and grain refinement, of a representative TRIP-HEA.
- To characterize the influence of temperature and strain rate on the microstructure evolution during hot compression.
- To establish a constitutive model for flow stress and determine the activation energy for the process.
Main Methods:
- Compression testing of a TRIP-HEA at temperatures ranging from 1123 K to 1273 K and strain rates from 0.1 s⁻¹ to 0.001 s⁻¹.
- Microstructural characterization to analyze grain structure evolution and dynamic recrystallization.
- Development of a constitutive equation correlating flow stress, strain rate, temperature, and strain.
- Estimation of apparent activation energy and analysis of the Zener-Hollomon parameter's influence.
Main Results:
- Discontinuous dynamic recrystallization (d-DRX) was identified as a key mechanism for grain refinement, especially at higher temperatures and lower strain rates.
- The volume fraction and morphology of recrystallized grains were found to be strongly dependent on the Zener-Hollomon parameter.
- An apparent activation energy of approximately 385.7 kJ/mol was estimated for the hot deformation process.
- A constitutive equation was successfully constructed, describing the relationship between processing parameters and material response.
Conclusions:
- Thermomechanical processing, particularly involving d-DRX, is effective for refining the grain structure of TRIP-HEAs.
- The findings provide critical insights into the hot deformation mechanisms of HEAs.
- This research offers practical guidelines for optimizing the microstructure and properties of HEAs through controlled thermomechanical processing.
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