pyMPEALab Toolkit for Accelerating Phase Design in Multi-principal Element Alloys

Multi-principal element alloys (MPEAs) occur at or nearby the centre of the multicomponent phase space, and they have the unique potential to be tailored with a blend of several desirable properties for the development of materials of future. The lack of universal phase diagrams for MPEAs has been a major challenge in the accelerated design of products with these materials. This study aims to solve this issue by employing data-driven approaches in phase prediction. A MPEA is first represented by numerical fingerprints (composition, atomic size difference , electronegativity , enthalpy of mixing , entropy of mixing , dimensionless $$\Omega$$ Ω parameter, valence electron concentration and phase types ), and an artificial neural network (ANN) is developed upon the datasets of these numerical descriptors. A pyMPEALab GUI interface is developed on the top of this ANN model with a computational capability to associate composition features with remaining other input features. With the GUI interface, an user can predict the phase(s) of a MPEA by entering solely the information of composition. It is further explored on how the knowledge of phase(s) prediction in composition-varied $$\hbox {Al}_x$$ Al x CrCoFeMnNi and $$\hbox {CoCrNiNb}_x$$ CoCrNiNb x can help in understanding the mechanical behavior of these MPEAs. Graphic Abstract

Selection of High Entropy Alloy for Solid Solution Using Multi-Criteria Decision Making Tool

High entropy alloys (HEA’s) have found a very special place in aerospace industries due to their property of forming solid solution. In past literatures on high entropy alloys, it is established that parameters like atomic size difference (), topological parameter (Ω) and electro-negativity difference (∆) plays a vital role in deciding whether solid solution will be formed or not. Therefore, the present study deals with the selection of optimal high entropy composition based on the three parameters δ, Ω and with the help of TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution). Ranking is done for 38 HEA different compositions such that the first rank represents the HEA which is most likely to form solid solution. The study reveals that TOPSIS method can be successfully implemented to predict the formation of solid solution in HEA’s.

Effect of Atomic Size Difference on the Microstructure and Mechanical Properties of High-Entropy Alloys

The effects of atomic size difference on the microstructure and mechanical properties of single face-centered cubic (FCC) phase high-entropy alloys are studied. Single FCC phase high-entropy alloys, namely, CoCrFeMnNi, Al0.2CoCrFeMnNi, and Al0.3CoCrCu0.3FeNi, display good workability. The recrystallization and grain growth rates are compared during annealing. Adding Al with 0.2 molar ratio into CoCrFeMnNi retains the single FCC phase. Its atomic size difference increases from 1.18% to 2.77%, and the activation energy of grain growth becomes larger than that of CoCrFeMnNi. The as-homogenized state of Al0.3CoCrCu0.3FeNi high-entropy alloy becomes a single FCC structure. Its atomic size difference is 3.65%, and the grain growth activation energy is the largest among these three kinds of single-phase high-entropy alloys. At ambient temperature, the mechanical properties of Al0.3CoCrCu0.3FeNi are better than those of CoCrFeMnNi because of high lattice distortion and high solid solution hardening.

Effects of Nitrogen Content on the Structure and Mechanical Properties of (Al0.5CrFeNiTi0.25)Nx High-Entropy Films by Reactive Sputtering

In this study, (Al0.5CrFeNiTi0.25)Nx high-entropy films are prepared by a reactive direct current (DC) magnetron sputtering at different N2 flow rates on silicon wafers. It is found that the structure of (Al0.5CrFeNiTi0.25)Nx high-entropy films is amorphous, with x = 0. It transforms from amorphous to a face-centered-cubic (FCC) structure with the increase of nitrogen content, while the bulk Al0.5CrFeNiTi0.25 counterpart prepared by casting features a body-centered-cubic (BCC) phase structure. The phase formation can be explained by the atomic size difference (δ). Lacking nitrogen, δ is approximately 6.4% for the five metal elements, which is relatively large and might form a BCC or ordered-BCC structure, while the metallic elements in this alloy system all have a trend to form nitrides like TiN, CrN, AlN, and FeN. Therefore, nitride components are becoming very similar in size and structure and solve each other easily, thus, an FCC (Al-Cr-Fe-Ni-Ti)N solid solution forms. The calculated value of δ is approximately 23% for this multicomponent nitride solid solution. The (Al0.5CrFeNiTi0.25)Nx films achieve a pronounced hardness and a Young’s modulus of 21.45 GPa and 253.8 GPa, respectively, which is obviously much higher than that of the as-cast Al0.5CrFeNiTi0.25 bulk alloys.

Solid Solution Formation Criteria for High Entropy Alloys

The solid solution formation criteria for the equi-atomic ratio alloys were discussed. It is found that higher entropy of mixing (Smix>1.61R), less atomic size difference (δ<4.6), and near zero of the absolute value of the enthalpy of mixing (-2.685δ-2.54<Hmix <-1.28δ+5.44 KJ/mol) facilitate the formation of solid solution for the multi-principle components equi-atomic alloys.