Contrasting mechanical behavior in precipitation hardenable AlXCoCrFeNi high entropy alloy microstructures: Single phase FCC vs. dual phase FCC-BCC

In this study we developed a novel (TRIP+TWIP) high entropy alloy (HEA) with high specific strength and large ductility. First, by controlling the atomic constitution of the 3d transition metals (Cr, Mn, Fe, Co, and Ni), we designed a light-weight TRIP-assisted dual-phase HEA with a non-equiatomic composition of Cr22Mn6Fe40Co26Ni6, which exhibited 5% lighter density than the Cantor HEA. Secondly, we systematically added Al (a lightweight element (2.7 g/cm3), which has a large atomic size misfit with 3d transition metals, and Ferrite stabilizer) up to 5 at.% in Cr22Mn6Fe40Co26Ni6 HEA. With increasing Al content, the phase constitution of the alloy changed from a dual-phase of FCC and HCP (0 to 2.0 at.%) to a FCC single-phase (2.5 to 3.5 at.%), to a dual-phase of FCC and BCC (4.0 to 5.0 at.%). In particular, the (Cr22Mn6Fe40Co26Ni6)97.5Al2.5 HEA with the FCC single-phase exhibited a large Hall-Petch coefficient and relatively lower thermal conductivity due to its three times larger atomic size mismatch (δ) than the Cantor HEA, which causes the superior solid solution strengthening effect. Furthermore, the (Cr22Mn6Fe40Co26Ni6)96Al4.0 HEA, a boundary composition of BCC precipitation in the FCC phase, exhibited a 10% higher specific strength than the Cantor HEA as well as 50% larger strain, due to the unique TRIP and TWIP complex deformation mechanism. This result shows that the addition of Al in Cr22Mn6Fe40Co26Ni6 HEA can result not only in greater chemical complexity due to the multicomponent high entropy compositions, but also microstructural complexity due to the increase in competing crystalline phases. The confusion effect caused by both complexities lets the alloy overcome the trade-off relationship among conflicting intrinsic properties, such as strength versus ductility (or density). Consequently, these results pave the way for a new design strategy of a novel (TRIP+TWIP) HEA with high specific strength and large ductility.

Download Full-text

Microstructure and Tensile Mechanical Behavior of a Single-Phase Fe35Mn10Cr20Ni35 High-Entropy Alloy

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-05700-9 ◽

2021 ◽

Author(s):

Jun Zhou ◽

Hengcheng Liao ◽

Hao Chen ◽

Aijing Huang

Keyword(s):

Mechanical Behavior ◽

Single Phase ◽

High Entropy Alloy ◽

High Entropy

Download Full-text

A review on phase prediction in high entropy alloys

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211008935 ◽

2021 ◽

pp. 095440622110089

Author(s):

Vinay Kumar Soni ◽

S Sanyal ◽

K Raja Rao ◽

Sudip K Sinha

Keyword(s):

Solid Solution ◽

Phase Formation ◽

Single Phase ◽

High Entropy Alloy ◽

High Entropy Alloys ◽

Modeling Tools ◽

High Entropy ◽

Recent Developments ◽

Phase Prediction ◽

The Stability

The formation of single phase solid solution in High Entropy Alloys (HEAs) is essential for the properties of the alloys therefore, numerous approach were proposed by many researchers to predict the stability of single phase solid solution in High Entropy Alloy. The present review examines some of the recent developments while using computational intelligence techniques such as parametric approach, CALPHAD, Machine Learning etc. for prediction of various phase formation in multicomponent high entropy alloys. A detail study of this data-driven approaches pertaining to the understanding of structural and phase formation behaviour of a new class of compositionally complex alloys is done in the present investigation. The advantages and drawbacks of the various computational are also discussed. Finally, this review aims at understanding several computational modeling tools complying the thermodynamic criteria for phase formation of novel HEAs which could possibly deliver superior mechanical properties keeping an aim at advanced engineering applications.

Download Full-text