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The main goals of this work were to manufacture novel Al–Zn extruded alloys by varying the Zn content (0, 10, 20, 30 wt%), investigate the microstructural evolutions, hot deformation, and work hardening behaviour by hot compression test at different temperatures (25 °C, 75 °C, 150 °C, 225 °C, 300 °C). Al–20Zn alloy microstructure revealed α-Al and uniform distribution of (α + η) phases, coherent (α + η) crystals in GBs with casting defect-free surfaces, and effective interactions of pinning dislocations which led to improve mechanical performance of Al–20Zn alloy, as compared to the other alloys. The observed engineering stress–strain curve results revealed the decrease of stress with increasing of temperature due to flow softening, dynamic recovery and dynamic recrystallization. These results displayed also an increase of stress value with increasing of Zn content due to the precipitation of high density (α + η) phase in the matrix and GBs, increasing of forest and mobile dislocations density with strain fields, and the formation of fine dendrites. Work hardening rate (WHR) of extruded samples displayed three stages: stage I, WHR decreased slightly with increasing of temperature up to 75 °C and decreased drastically from 75 °C to 300 °C due to softening; stage II, WHR maintained constant due to balance between dislocation generations and dislocation annihilation; stage III, WHR slightly increased due to strain hardening of (α + η) phase. WHR was observed to increase considerably with increasing of Zn content due to the formation and dispersion of high density of (α + η) phase in the Al matrix and GBs. Deformation micro-localization in terms of different characteristics was examined and reported on the deformed samples after hot-compression test through SEM micrographs. [ABSTRACT FROM AUTHOR]

Al 7075 alloy matrix reinforced with different weight percentage of titanium borides (TiB2, 0, 1.5, 3, 4.5 and 6 wt%) and 1 wt% graphite (Gr) hybrid composites were synthesized by in-situ liquid metallurgy route, then the sliding wear characteristics were performed and investigated in this research work. TiB2 reinforced as 0, 1.5, 3, 4.5 and 6 wt% by the in situ chemical reaction of KBF4 and K2TiF6 salts and 1 wt% Gr with the Al 7075 matrix were added constantly in the melt. Several experiments were carried out to examine the wear behavior of the fabricated composite specimens through a tribometer at ambient temperature. The weight percentage of reinforcement (TiB2 particles), the applied load, the sliding velocity (SV), and the sliding distance (SD) were selected as process parameters at five different levels. The response surface methodology (RSM) was used to conduct the experiments as RSM is the feasible and accurate method employed for optimizing to set the parameters. To check the significance of the developed model by RSM, ANOVA and confirmatory tests were also accomplished. FESEM surface morphology was also carried out to illustrate the uniform dispersion of the TiB2–Gr particulates in Al 7075 matrix. The predicted wear characteristics from the developed model were well agreed with the experimental results. The obtained results were explained that both the increase in the percentage of RF and SV have dropped the wear loss (WL) curve whereas the load at all SVs and the SDs were uplifted the WL. The worn surface morphology explained that the adhesive mechanisms were dominated during the sliding wear test. Further, severe and mild wear occurred during higher load and lower load respectively. [ABSTRACT FROM AUTHOR]

Four component Cr0.21Fe0.20Al0.41Cu0.18 medium entropy alloy (Quaternary, 4C-MEA) and six component Cr0.14Fe0.13Al0.26Cu0.11Si0.25Zn0.11 high entropy alloy (sexinary, 6C-HEA) were designed and developed in non-equiatomic ratio to attain improved mechanical properties. These 4C-MEA, and 6C-HEA were synthesized via mechanical alloying (MA), and consolidated by hot pressing (HPing) at 723 K. For comparison, the same atomic ratio of four and six components of coarse grain alloys (4C-CGA and 6C-CGA) were also manufactured by conventional blending method. Nanocrystallite size powders of 27 ± 5.20 nm and 38 ± 3.7 nm were achieved for 4C-MEA and 6C-HEA respectively after 20 h MA. The phase evolutions, structural properties, and powder surface morphologies were characterized using X-ray diffraction and several electron microscopes. The 4C-MEA has possessed more quantity of body centred cubic (BCC) and less amount of face centred cubic (FCC) phases due to the more solid dissolution of 4 components. However, 6C-HEA exhibited more quantity of FCC and a small amount of BCC phases due to the incorporation of more FCC components compared to 4C-MEA and less solid dissolution due to more atomic radius difference among the mixing elements (atomic radius of Cr = 166 pm, Fe = 156 pm, Al = 118 pm, Cu = 145 pm, Si = 111 pm and Zn = 142 pm). The HPed samples produced ultra-fine crystallite size of 177 nm and 499 nm for 4C-MEA and 6C-HEA respectively. Further, 4C-MEA and 6C-HEA exhibited the ultimate compressive strength (UCS) of 365 MPa and 456 MPa respectively due to dissolution and lattice distortion of mixing elements. Also, 6C-HEA possessed Vickers hardness strength of around 1.97 GPa which was 2 times higher than 4C-MEA. The theoretical background of various strengthening mechanisms, various physicochemical, thermodynamic parameters, and four core effects behind the improved properties in entropy alloys was discussed and reported. The dislocation strengthening and solid solution strengthening were the major factors in exhibiting more UCS in 4C-MEA and 6C-HEA than 4C-CGA and 6C-CGA. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEAs) are being attracted recently by several researchers, scientists, and academicians to achieve extraordinary and outstanding properties that cannot be obtained from conventional alloys. HEAs are multicomponent alloys in which a minimum of five metallic elements are mixed in an equal molar or non-equal molar ratio. The rapid growth of this field produces a huge amount of scientific papers over the last decade. However, still, there is a need to review various manufacturing methods and their results. Also, the outcome of the scientific articles related to HEAs has ignored the various methods of synthesizing and manufacturing. In this review article, an attempt was made and largely concentrated on the methods and techniques that can be used in the manufacturing and synthesizing of the HEAs. Recently, the properties of HEAs become much better when compared to conventional alloys. Some techniques have succeeded in producing ultrafine microstructure grains which become a leap in industrial fields. Now, the manufacturing methods of conventional alloys are almost familiar and implemented according to the suggestions given by the researchers and academicians based on their work. Therefore, the present review article has demonstrated various methods of manufacturing of HEAs with novel schematics with a preview description for more understanding of the basic work criteria. Besides, this article has reviewed the outcomes of several research articles related to several methods, then compared the outcome of each method with the corresponding mechanical properties, and major challenges of HEAs are discussed and reported. [ABSTRACT FROM AUTHOR]