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In this work, the continuous hot-compaction behavior of Quinary-FeCrCuMnTi, Senary-FeCrCuMnTiV, and Septenary-FeCrCuMnTiVZn equiatomic nanostructured high-entropy alloys (HEAs) was studied from 0 to 550 MPa pressure in a universal testing machine. These alloys were synthesized by mechanical alloying and characterized by HRSEM and HRTEM. The synthesized powders were compacted at different temperatures (RT to 525°C) using a universal testing machine operated at 10 mm per minute. Microstructural results demonstrated that multiphase solid solutions were obtained in all the HEAs. Septenary-FeCrCuMnTiVZn HEA has produced a higher amount of FCC phase compared to other alloys due to the incorporation of low melting Zn atoms enhancing solid solutions leading to produce a lower value of FCC phase crystallite size (7.8 nm). The continuous hot-compaction results explained that the percentage relative density was increased drastically after 225°C due to the elimination of internal stress, and decreased dislocation density. Senary-FeCrCuMnTiV HEA exhibited a higher percentage of relative density in all operating conditions due to more crystallite size, lower value of powder particle sizes, and the domination of BCC-V atoms in addition to high-configurational entropy. The experimental relative density-pressure data were fitted linearly using the Panelli and Ambrozio Filho equation for exploring the plastic deformation ability of developed powder particles. [ABSTRACT FROM AUTHOR]

In the present work, the room temperature deformation behavior of dezincification-resistant (DZR) brass was performed by varying strain rates (1 × 10−4 s−1, 0.55 × 10−3 s−1, 1 × 10−3 s−1, 0.55 × 10−2 s−1, 1 × 10−2 s−1) and percent cold works (15 to 65% with step of 10%). These parameters are important to plumbing parts of its forming. Room temperature deformation workability map was developed that provides the selection of safe deformation parameters without cracking. The as-received and deformed DZR brass samples were carefully characterized by various microscopes. The results revealed that more dislocations lines and twinning were observed through transmission electron microscope images as the strain rate (SR) increases which led to early failure of the sample before reaching the set height reduction. It was determined that more amount of strain hardening with designed height reduction was achieved at lower SR whereas less amount of strain hardening was achieved at higher SR due to strain mismatching phenomenon and various deformation mechanisms. [ABSTRACT FROM AUTHOR]

The densification behavior of FeCrCuMnTi (HEA1), FeCrCuMnTiV (HEA2), and FeCrCuMnTiVZn (HEA3) equiatomic high-entropy alloys (HEAs) was explored using different uniaxial quasi-static controlled compaction (1 mm/min). These HEAs were synthesized by mechanical alloying (MA, speed: 300 rpm, BPR: 10:1, time: 25 h). Various phase formations, structural characteristics (crystallite size, lattice strain, and lattice constant), thermo-dynamic calculations, powder surface morphologies, detailed microstructural evolutions, and chemical compositions were examined using X-ray diffraction, high-resolution scanning electron microscopy, and high-resolution transmission electron microscopy. The XRD results revealed the formation of multiple solid solutions (FCC, BCC, and HCP) due to the variation in entropy, and the presence of high-strength elements (Cr, Ti, and V) in the developed HEA alloys. The synthesized powders were consolidated into bulk green samples with different compaction pressures starting from 25 to 1100 MPa under as-milled and milled under stress recovery conditions (150 °C, 1 h). The incorporation of V in the FeCrCuMnTi HEA resulted in improved densification due to a greater reduction in particle size, and high configurational entropy. Furthermore, the stress-recovered powder samples produced more relative density owing to the elimination of lattice strain. Several linear and non-linear compaction models were applied to predict densification behavior. The non-linear Cooper and Eaton model produced the highest regression coefficients compared to the other models. [ABSTRACT FROM AUTHOR]

• Synthesized Nanocrystallite Entropy Alloys. • Examined the structural properties and characterizations effectively. • Extensive mechanical properties were achieved. • Studied the various strengthening mechanisms. The present research work has concentrated to synthesize nanocrystalline (NC) Cr 0.26 Fe 0.24 Al 0.5 (medium entropy alloy, 3E-MEA) and Cr 0.15 Fe 0.14 Al 0.30 Cu 0.13 Si 0.28 (high-entropy alloy, 5E-HEA) non-equiatomic (equal weight fraction) alloys through mechanical alloying (MA); which studied the influence of entropy effect on structural properties, microstructural characterization, and mechanical behaviour. Further, the same non-equiatomic ratio of two coarse grain alloys (CGAs) was manufactured by conventional powder metallurgy (PM) route (blending method, 3E-CGA, 5E-CGA) for comparison. All synthesized powders were hot-pressed (HPed) at 723 k for 30 min subsequently mechanical properties in terms of compressive stress-strain and hardness were examined. The samples of as-milled powders, HPed, and fractured were investigated using X-ray diffraction (XRD) and advanced electron microscopes. The HPed sample of 3E-MEA of Cr 0.26 Fe 0.24 Al 0.5 produced 94% BCC and 6% FCC crystal structures due to more dissolution of Al atoms in the stronger bonding atoms of Cr-Fe lattice. Whereas 5E-HEA of Cr 0.15 Fe 0.14 Al 0.30 Cu 0.13 Si 0.28 sample has exhibited 72.1% FCC phase and 27.9% BCC phase due to balance between the dissolution of FCC elements (Al, Cu, Si) and BCC elements (Cr, Fe). Further, 3E-MEA and 5E-HEA have exhibited the ultimate compressive strength (UCS) of 1278 ± 6.75 MPa and 2060 ± 2.8 MPa respectively whereas the corresponding conventionally blended alloys produced 268 ± 5 MPa and 615 ± 3 MPa for 3E-CGA and 6E-CGA respectively. Vicker's hardness strength (VHS) of 5E-HEA of Cr 0.15 Fe 0.14 Al 0.30 Cu 0.13 Si 0.28 has exhibited 68% more when compared to 3E-MEA of Cr 0.26 Fe 0.24 Al 0.5 , 3.26 times higher compared to blended alloys. Further, several strengthening mechanisms on the mechanical behaviour of MEA and HEA were investigated in which dislocation strengthening mechanisms followed by solid solution strengthening mechanisms have influenced more as compared to grain boundary strengthening mechanisms. [ABSTRACT FROM AUTHOR]

The present investigation demonstrated the manufacturing of Al – x wt.% Zn (x = 0, 10, 20, & 30) die-casting alloys through liquid metallurgy route followed by squeezing and hot-extrusion processes. The phase analyses and microstructural evolutions were investigated by x-ray diffractometer and electron microscopes (FESEM with EDAX, EBSD, and HRTEM) respectively. The mechanical behaviour was examined by the Vickers micro-hardness and tensile tests. The results revealed that the solid solution formation of the Al-Zn phase (α+η) along with an individual α-Al phase was obtained. The distribution of (α+η) nanocrystallites nucleates in the α-Al and (α+η) major phases was observed with the formation of spider-leg like dislocations due to thermal misfit. Hot-extruded alloys exhibited different structural changes, namely, grains flow pattern, cracking/fragmentation, redistribution, shrinkages, porosities, and micron-sized voids. Al-20Zn alloy exhibited improved microstructural observation whereas Al-30Zn alloy displayed more shrinkages and porosities. The EBSD analyses illustrated the variation in grain flow patterns (coloured maps) and deformation mean uniform density (pole figures) values with the solid solution of Zn addition. The Al – 20Zn alloy exhibited improved mechanical properties (strength and ductility) owing to the effective solid solution of α-Al with the precipitated coherent α+η phases in addition to the absence of defects which can be recommended for die-casting products. [ABSTRACT FROM AUTHOR]