A Study on the Hall-Petch Relationship and Grain Growth Kinetics in FCC-Structured High/Medium Entropy Alloys

Area of Science:

• Materials Science
• Metallurgy
• Physical Chemistry

Background:

• High and medium entropy alloys (H/MEAs) offer tunable properties for advanced applications.
• Understanding recrystallization and grain growth is crucial for optimizing alloy performance.
• The Hall-Petch relationship governs the mechanical behavior of many metallic materials.

Purpose of the Study:

• To investigate the recrystallization, grain growth kinetics, and hardness of FeCoNiCrPd and FeCoNiCrMn H/MEAs.
• To determine the factors influencing the Hall-Petch coefficient (K_H) and grain growth parameters (n, k, Q).
• To compare the properties of these H/MEAs with conventional alloys.

Main Methods:

• Annealing of homogenized and cold-rolled FeCoNiCrPd and FeCoNiCrMn alloys.
• Microstructural analysis to determine grain size.
• Hardness testing to evaluate mechanical properties.
• Calculation of Hall-Petch parameters, grain growth kinetics, and activation energy.

Main Results:

• Grain size and hardness of the studied H/MEAs follow the Hall-Petch equation.
• The Hall-Petch coefficient (K_H) is primarily influenced by stacking fault energy and shear modulus.
• FeCoNiCrPd alloy demonstrated the highest hardness due to a significant Young's modulus difference between Cr and Pd.
• Grain growth kinetics were quantified using the Arrhenius equation, with high activation energy (Q) observed, particularly in FeCoNiCrPd due to lattice distortion.

Conclusions:

• The Hall-Petch relationship effectively describes the mechanical behavior of these H/MEAs.
• Stacking fault energy and shear modulus are key factors determining hardness.
• FeCoNiCrPd exhibits exceptional hardness and suppressed grain growth, attributed to its unique composition and lattice distortion.
• The high activation energy for grain growth in these H/MEAs suggests enhanced thermal stability compared to conventional alloys.