A perspective on precipitation-hardening high-entropy alloys fabricated by additive manufacturing

Recently, the materials research community has seen a great increase in the development of multicomponent alloys, known as high entropy alloys (HEAs) with extraordinary properties and applications. In surface protection and engineering, diverse applications of HEAs are also being counted to benefit from their attractive performances in various environments. Thermally sprayed HEA coatings have outperformed conventional coating materials and have accelerated further advancement in this field. Therefore, this review article overviews the initial developments and outcomes in the field of HEA coatings. The authors have also categorized these HEA coatings in metallic, ceramic, and composite HEA coatings and discussed various developments in each of the categories in detail. Various fabrication strategies, properties, and important applications of these HEAs are highlighted. Further, various issues and future possibilities in this area for coatings development are recommended.

https://www.mdpi.com/2079-6412/11/4/372/pdf

High Entropy Alloy Coatings and Technology

Toward excellent tensile properties of nitrogen-doped CoCrFeMnNi high-entropy alloy at room and cryogenic temperatures

Superior antifouling properties of a CoCrFeMnNi high-entropy alloy

In this study, equimolar AlCuSiFe-x (x = Cr, Mn, Zn, Sn) HEAs were fabricated by mechanical alloying (MA) and spark plasma sintering methods (SPS). The MA was performed for 45 h followed by densification of powder compacts at 650 °C. The results revealed the formation of dual face-centered cubic (FCC) and body-centered cubic (BCC) structures in AlCuSiFe-x (x = Zn, Sn) while a single BCC solid solution was noticed in AlCuSiFe-x (x = Cr, Mn). After SPS treatment, AlCuSiFeSn alloy contained FCC with CuxSny while AlCuSiFe–Zn changed to FCC + BCC structure. Similarly, AlCuSiFeCr and AlCuSiFeMn showed the formation of BCC + FCC with additional σ- and µ-phases in the HEA matrix. The calculated thermodynamic parameters of HEAs also supported the formation of different solid-solution phases in each of the above HEAs. It was found that HEAs with the additive elements Sn and Zn tend to have major FCC phases, while those with Cr and Mn give rise to major BCC with brittle σ- and µ-phase, which further improves their mechanical strength. 

https://link.springer.com/content/pdf/10.1007/s12540-021-01125-0.pdf

Effect of Additive Elements (x = Cr, Mn, Zn, Sn) on the Phase Evolution and Thermodynamic Complexity of AlCuSiFe-x High Entropy Alloys Fabricated via Powder Metallurgy

In this study, we synthesized a new Al16.6Cu16.6Fe16.6Mn16.6Mg16.6Ti16.6 lightweight high entropy alloy (LWHEA) by high energy ball milling and spark plasma sintering (SPS). The effect of milling time (15, 30, 45, and 60 h) and SPS conditions (600 and 700 °C) on microstructure, hardness, and density of LWHEAs were studied. The results showed that milled LWHEA is base centered cubic (BCC) structured, consisting of dual BCC1/BCC2 matrix with dispersed minor Cu2Mg precipitates and Ti. After SPS of milled samples, the BCC2 phase fraction was increased gradually. The distribution of Ti was uniform up to 45 h milled sample SPSed at 600 °C. However, porosity was built up beyond 45 h milling and higher SPS temperature (700 °C). The presence of finer secondary phases in the HEA matrix contributes to the dispersion hardening. The optimum microhardness and density of LWHEA AlCuFeMnMgTi were around 770 HV and 4.34 g cm− 3 which is superior to other conventional alloys such as Al or Ti-based alloys.

https://link.springer.com/content/pdf/10.1007/s12540-020-00823-5.pdf

Lightweight AlCuFeMnMgTi High Entropy Alloy with High Strength-to-Density Ratio Processed by Powder Metallurgy

Novel AlCuFeMnTi–X high-entropy alloy (HEA) powder mixture with individual X = Mg, Si, Zn was mechanically alloyed for 45 h and consolidated at 700°C by spark plasma sintering (SPS). The effect of ...

Effect of light (X = Mg, Si) and heavy (X = Zn) metals on the microstructural evolution and densification of AlCuFeMnTi-X high-entropy alloy processed by advanced powder metallurgy

In this work, we have investigated the role of high-energy ball milling (HEBM) on the evolution of microstructure, thermal, and wetting properties of an Sn-0.7Cu alloy. We ball-milled the constituent Sn and Cu powders in eutectic composition for 45 h. The microstructural studies were carried out using optical and scanning electron microscopy. The melting behavior of the powder was examined using differential scanning calorimetry (DSC). We observed a considerable depression in the melting point of the Sn-0.7Cu alloy (≈7 °C) as compared to standard cast Sn-0.7Cu alloys. The resultant crystallite size and lattice strain of the ball-milled Sn-0.7Cu alloy were 76 nm and 1.87%, respectively. The solderability of the Sn-0.7Cu alloy was also improved with the milling time, due to the basic processes occurring during the HEBM.

https://www.mdpi.com/2075-4701/10/3/370/pdf

Myoung Jin Chae

Papers

Lightweight AlCuFeMnMgTi High Entropy Alloy with High Strength-to-Density Ratio Processed by Powder Metallurgy

Effect of light (X = Mg, Si) and heavy (X = Zn) metals on the microstructural evolution and densification of AlCuFeMnTi-X high-entropy alloy processed by advanced powder metallurgy

Solderability, Microstructure, and Thermal Characteristics of Sn-0.7Cu Alloy Processed by High-Energy Ball Milling