Evaluating the solid solution, local chemical ordering, and precipitation strengthening contributions in multi-principal-element alloys

Numerous theoretical and experimental studies suggest that the chemical ordering microstructure plays an important role for the strength and plastic deformation in the multi-principal-element alloy (MPEA). Despite the importance of this fact has been well confirmed, little is known about the influence of chemical ordering degree from the atomic scale to nano scale for the nanocrystal MPEA over a wide grain size range. In the present work, considering the abnormal local stacking fault energy originated from the heterogeneous chemical element concentration, the modified Hall-Petch relationship is elaborately established in MPEA, quite different from the traditional alloys. Additionally, the effects of the solid solution, local chemical ordering, and precipitation on the strengthening contribution and strain partition are evaluated. The increase of the chemical ordering degree improves the stacking fault energy and deformation gradient, as well as microrotation field. This trend leads to the yield strength owing to the formation of the slender shear bands. The geometry of the ordered structure is deformed and twisted to a certain extent, for the compatible plastic deformation. This work gives the atomic understanding of chemical-ordering-degree dominated strengthening mechanisms, to develop the strong and ductile MPEAs with desired properties. The data that support the findings of this study are available from the corresponding author upon reasonable request.