Microstructural evolution and mechanical characterization for the AlCoCrFeNi_2.1 eutectic high‐entropy alloy under different temperatures

Abstract

Recently, there has been a lot of interest in the AlCoCrFeNi2.1 eutectic high‐entropy alloys (EHEAs), which can achieve a good balance of strength and ductility. The relationship between the microstructure and mechanical properties of the alloy was established in this study by examining the microstructural evolution during heat treatment of 500–1000°C. The results show that the alloy's microstructure remained unchanged when the heat treatment temperature was lower than 700°C. With further rise above 800°C, the B2II precipitates were inspected in the L12 matrix. Besides, L12II started to be precipitated from the B2 matrix at 900°C. The tensile test results conducted at 20–1000°C showed that both the yield strength and ultimate tensile strength decreased as the temperature rose. As for the elongation, however, it increased dramatically when the testing temperature was over 800°C, being attributed to the dynamic recrystallization. The results obtained provided a fundamental understanding of high‐temperature properties for duplex HEAs.

Creep behavior and life prediction of a reactor pressure vessel steel above phase‐transformation temperature via a deformation mechanism‐based creep model

“…Furthermore, the dislocation climb-plus-glide mechanism may involve dislocation multiplication from Frank-Reed sources, which eventually leads to the tertiary creep behavior at an accelerated creep rate. As the above mechanisms are operated under the true stress condition in real specimens due to the incompressibility of plastic flow, the true stress and strain are given by 31,32…”

“…Furthermore, the dislocation climb‐plus‐glide mechanism may involve dislocation multiplication from Frank‐Reed sources, which eventually leads to the tertiary creep behavior at an accelerated creep rate. As the above mechanisms are operated under the true stress condition in real specimens due to the incompressibility of plastic flow, the true stress and strain are given by 31,32 where σ 0 is the engineering (nominal) stress, ε is the true strain, and ε 0 is the engineering strain. Taking the true stress–strain relationship into Equation (1) and also considering dislocation multiplication by the first approximate of the Taylor series, the SSCR of dislocation‐climb‐plus glide can be calculated 21 : where M is the dislocation multiplication factor and A' is expressed as …”

High-Temperature Mechanical Behavior of Cobalt-Free FeMnCrNi(Al) High-Entropy Alloys

“…This also indicates that the addition of the element Al enhances the thermal stability of the alloy. The A973 alloy has high strengths below 673 K, approaching that of the coherent nanoprecipitation-strengthened superalloys and several eutectic alloys [19,26,28]. However, the thermal stability of the alloy is poor, and the properties of the alloy considerably decrease after 673 K. The thermal stability of the semi-coherent interface is much worse than that of the coherent interface.…”

“…Furthermore, the presence of the element Al increases the oxidation resistance of the alloys [18]. The AlCoCrFeNi 2.1 eutectic high-entropy alloy, composed of the ordered FCC phase (L1 2 ) and the ordered body-centered cubic phase (B2), exhibits exceptional mechanical properties at temperatures below 973 K [19]. However, the temperature sensitivity of semi-coherent body-centered cubic (BCC) or B2 precipitates remains uncertain.…”