# Structural Particularities, Prediction, and Synthesis Methods in High-Entropy Alloys
## 4 Conclusions  
High-Entropy Alloys (HEAs) have emerged as a groundbreaking class of materials with exceptional properties and a wide range of potential applications. This article has examined the influence of various synthesis methods on the microstructure and mechanical properties of HEAs. It has been demonstrated that different fabrication techniques, including casting, mechanical alloying, powder metallurgy, and additive manufacturing, significantly affect the phase composition, structural integrity, and mechanical performance of HEAs. The key findings of this brief review study include:  
* Microstructural Impact: The choice of synthesis method leads to diverse microstructures. For example, direct laser synthesis and arc melting produce different textures and structures, such as dendritic and Widmanstatten, due to varying solidification conditions. * Phase Evolution: The evolution of phases in HEAs is influenced by parameters like grinding duration, ball-to-powder ratio, initial structure, and mixing order during mechanical alloying and spark plasma sintering. Similarly, cooling rates and local atomic arrangements during melting and casting impact phase stability and microstructure. * Mechanical Properties: The mechanical properties, including hardness, ductility, and tensile strength, are significantly influenced by the synthesis method. Additive manufacturing techniques like selective laser melting (SLM) and laser powder bed fusion (LPBF) enhance these properties through rapid cooling rates and refined microstructures. In addition to traditional synthesis methods, the integration of advanced prediction methodologies and machine learning approaches has opened new avenues for HEA development. In particular, machine learning methods have demonstrated potential in forecasting phase formation and stability in HEAs by examining extensive datasets of \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Composition of HEA Alloy**} & \multicolumn{2}{c}{**Melting-Casting**} & \multicolumn{2}{c}{**MA + SPS**} & \multicolumn{2}{c}{**AM**} \\ \cline{2-7}  & **Phases** & **Mechanical Properties** & **Phases** & **Mechanical Properties** & **Phases** & **Mechanical Properties** \\ \hline CoCrFeNiMn & FCC [84; 85] & - & FCC [88] & \begin{tabular}{c} Rc = 1987 MPa \\ Vickers hardness = 646 HV \\ \end{tabular} & \begin{tabular}{c} FCC + BCC \\ [82; 89; 90] \\ \end{tabular} & \begin{tabular}{c} Rt = 601 MPa \\ \end{tabular} \\ \cline{2-7} CoCrFeNiAl\({}_{0.3}\) & FCC [91; 92] & \begin{tabular}{c} UTS = 528 MPa \\ YTS = 257 MPa \\ \end{tabular} & FCC + BCC [78] & \begin{tabular}{c} Rc = 1907 MPa \\ Vickers hardness = 625 HV \\ \end{tabular} & FCC [93] & \begin{tabular}{c} UTS = 896 MPa; \\ YS = 730 MPa \\ \end{tabular} \\ \cline{2-7} CoCrFeNi & - & - & FCC + Cr/C3 [94] & \begin{tabular}{c} Vickers hardness = \\ 580 HV \\ \end{tabular} & FCC [95] & - \\ \cline{2-7} AlCoCrCuFeNi & FCC + BCC [96] & \begin{tabular}{c} Hardness = 5.056 GPa \\ Rc = 1.82 GPa \\ \end{tabular} & FCC + BCC [97] & \begin{tabular}{c} Hardness = 8.13 GPa \\ Elastic modulus = 172 GPa \\ \end{tabular} & BCC [98] & - \\ \cline{2-7} TZrNbMo\({}_{0.3}\)V\({}_{0.3}\) & BCC [99] & \begin{tabular}{c} YS = 1312 MPa \\ \end{tabular} & - & - & FCC + BCC [100] & - \\ \cline{2-7} N\({}_{1.5}\)Co\({}_{1.5}\)CrFeTi\({}_{0.5}\) & FCC [101] & \
\begin{tabular}{c} YS = 996 MPa \\ Rc = 1502 MPa Vickers \\ hardness = 515 HV \\ \end{tabular} & FCC [102] &
\begin{tabular}{c} Vickers hardness = \\ 442 HV Elastic \\ modulus = 216 GPa \\ Rt = 1384 MP \\ \end{tabular} & - & - \\ \hline \hline \end{tabular}  
* UTS = ultimate tensile strength; YTS = yield tensile strength; Rc = compression strength; Rt = tensile strength; YS = yield strength.  
\end{table} 
Table 3: Influence of the synthesis method of HEA alloys on their microstructure and mechanical properties. thermodynamic and experimental data.