Effect of thermo-mechanical treatment on microstructure, mechanical properties, and strengthening mechanism of (CoCrFeNiMo0.1)Al0.03 high entropy alloy

Y Su and HW Ma and JC Xiang and BR Xue and KX Tong and YC Zhao, JOURNAL OF ALLOYS AND COMPOUNDS, 1043, 184252 (2025).

DOI: 10.1016/j.jallcom.2025.184252

The mutual constraint between the strength and plasticity of high- entropy alloys (HEAs) severely limits their large-scale engineering applications. In this work, a series of (CoCrFeNiMo0.1)Al0.03 HEAs with face-centered cubic (FCC) structure were prepared by adjusting the heat treatment temperature in the cold rolling-heat treatment process technology. The specimen heat-treated at 600 degrees C exhibits ultra- high strength (i.e., over 1270 MPa), while the as-cast specimen shows ultra-high plasticity (i.e., 91.6 +/- 2.1 %). Notably, the specimen heat-treated at 800 degrees C combines high strength (920 +/- 25 MPa) and high plasticity (57.8 +/- 1.1 %). The reason for the above phenomena can be attributed to the fact that the alloy with a reasonable composition has a low stacking fault energy (19.02 mJ/m2), which can activate deformation-induced twinning (TWIP) strengthening. A reasonable heat treatment temperature can result in a reasonable grain size. Meanwhile, the nano-scale body-centered cubic (BCC) structured Cr and sigma-CrMo precipitates can effectively block the movement of dislocations (i. e., form dislocation pile-ups), and twins also have a strong hindering effect on dislocations. These phenomena prove that the alloy has a strong heterogeneous deformation-induced (HDI) strengthening effect. Molecular dynamics (MD) simulations also confirm that a large number of stacking faults and twins are formed in this alloy system, which have a strong pile-up effect on dislocations. This work can provide guidance for subsequent research on HEAs to overcome the strength-plasticity trade-off relationship.

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