Abstract
In this study; the effect of aging treatment for 4 h at 600–1000 °C on the microstructure and properties of a Fe55(CoCrNi)10(MoV)5C5 medium-entropy alloy (MEA) was investigated. After the alloy was aged at 800 °C, a large number of granular and rod-shaped particles are formed throughout the face-centered cubic (FCC) matrix. The average particle diameter was measured to be approximately 46 nm, and the result of transmission electron microscopy (TEM) analysis verified that these secondary precipitates are VC carbides, which plays an important role for pinning dislocations and hindering dislocation movement. Therefore, the hardness and ultimate tensile strength of the alloy at this state increased from 253 HV, 322 MPa in cast condition to 326 HV, 626 MPa, respectively, while remaining relatively good elongation (6.2%). As the aging temperature increases, the volume fraction of the VC carbides decreased while its sizes increased; thus, the dispersion strengthening effect was reduced, resulting in the decrease in the hardness and strength.
Highlights
High-entropy alloys (HEAs) are defined as alloys composed of five or more principal elements with the molar ratio of each principal element between 5% and 35% [1]
The hardness peak appears at 800 ◦ C and increases from 253 HV in cast condition to 326 HV
When the temperature exceeds 800 ◦ C, the hardness decreases gradually and reaches 289 HV at 1000 ◦ C, indicating that the hardness still maintained a relatively high value compared to the hardness of the as-cast alloy even at a very high temperature
Summary
High-entropy alloys (HEAs) are defined as alloys composed of five or more principal elements with the molar ratio of each principal element between 5% and 35% [1]. HEAs are mainly manifested as the following four core effects: high configuration entropy in thermodynamics, sluggish atomic diffusion in kinetics, severe lattice distortion effect in structure, and “cocktail” effect in performance [4]. Due to their unique high-entropy effect, HEAs are easy to form a simple solid solution structure rather than intermetallic compounds, exhibiting high strength, high hardness, good ductility, and excellent thermal stability [13,14,15,16,17]. Precipitation strengthening is an effective method to improve the strength of FeCoCrNi HEA. T T shun et al [19] have investigated the aging-hardening of the FeCoCrNiMo0.85 HEA after aging at 700–1000 ◦ C, and they found that the σ phase can be completely
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