The mechanical alloying technique was employed to produce series of high entropy alloys, combining in equiatomic percentage Al, Co, Cr, Cu, Fe, Mo, Ni and Ti. Milling times were 0, 10, 20 and 30 h, and experiments were performed in a high energy ball mill (SPEX-8000M) under argon atmosphere. The structural and microstructural changes due to mechanical alloying process were studied by X-ray diffraction and electron microscopy. Although there is the presence of pure elements with HCP crystalline structure, the XRD patterns of as-milled powders revealed the presence of a mixture of nanocrystalline solid solution with FCC and BCC structure phases. The hardness of the powder samples was evaluated by Vickers microhardness testing. The average microhardness values indicate that the alloy with the greatest hardness is the NiCoAlFeMoCr.

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Cadmium sulfide (CdS) is a type II-VI semiconductor widely used as photosensitizer in various wide band-gap metal oxides and in visible-light photocatalyst for H 2 evolution, due to its satisfactory bandgap (2.4 eV) that matching with the average spectrum of sunlight [1]. Usually, this material has been obtained in the nanocrystalline form by chemical route (bath deposition), using some organic molecules as precursors (hydrazine, thiourea, thioacetamide, dimethylcadmium etc.); however, some reagents commonly used in this route are costly, toxic, flammable and carcinogen [2]. Thus, some alternative routes have been explored, one of them based on processing in solid state, is called mechanical milling (MM) [3,4], where cadmium (Cd) and sulphur (S) are used as precursors for the CdS synthesis. The source of the anion sulphide is S, which has the advantage that is non-toxic for the human body.

Al-2024 is a Cu-rich heat treatable alloy which is used in aerospace applications because of its high strength/weight ratio, as well good fatigue resistance [1]. Precipitation heat treatments are an important procedures that directly affects the mechanical properties of the material. An important step of such treatments is solubilization, where the main objective consist in maintain the maximum amount of solute phases in solid solution, where the processing time is a critical variable to control to obtain a satisfactory degree of solubilized [2]. The addition of Zn to the 2024 alloy has been investigated and reported by various authors, Zn and Al have a difference of 7% in the atomic radius [3], which represents some advantages from structural viewpoint due the mechanism of hardening by solid solution.Studies on thermo-mechanical treatment of aluminum alloys start from 196Os [4,5]. Thermo-mechanical treatments are divided into intermediate thermo-mechanical treatment (ITMT) and final thermo-mechanical treatment (FTMT) by Russo and coworkers [5]. ITMT involves high temperature, which focuses on grain morphologies refining, as-cast microstructures modification and depleting component segregation. FTMT includes low temperature age hardening by deformation and precipitation.The aim of this work is to evaluate the effect of solubilization temperature, Zn addition and thermo-mechanical treatments on the Al-2024 alloy. The alloy fabrication with Zn additions (0.25 to 0.75 wt. %) was made by conventional direct casting, the melt was degassed with argon gas (20 PSIg) for 5 min period and AlTiB was added as grain refiner (0.13 % weight).Zn modification was performed with the addition of a ZnAl master alloy (Zn72.7-Al27-Cu0.2 Mg-0.1), commercially known as ZA27. The ITMT treatment consisted in hot rolling at 490°C, 50% of thickness reduction and solubilization (495°C) with different times. The FTMT treatment involved 5 to 10% thickness reduction by cold rolling and a final aging step (195°C) at several times. The microstructural characterization was done using an optical microscope ZEISS model Scope A1 and a SEM JEOL model JSM 5800-LV The Fig. 1 shows representative images of 2024-0.25 Zn alloy after heat treatment of solubilization for different times. It can be seen as decrease segregation of solute in the interdendritic region in function of time of solubilized. The Fig. 2 shows representative images of Al-2024 alloy with different additions of Zn after ITMT processing. It is noticeable the thermo-mechanical treatment effect on the casting structure: as randomly oriented grains with identical properties in all directions (isotropy). However, after hot rolling, grains are textured and the properties change at different directions (anisotropy). It is worth mentioning that we are working to complete the characterization for all conditions via SEM and TEM.

The Al-2024 alloy as a heat-treatable material, exhibits certain excellent properties, such as high tensile strength, good damage tolerance and creep resistance. With the excellent thermal stability, these alloys are considered to be candidate materials for future applications in the aerospace industry [1]. Actually, recent demand for weight reduction in structural component calls for further enhancement of strength of commercial structural alloys. Increasing recognition has been given to the thermos-mechanical treatments recently as important techniques for improving the properties of metallic materials [2]. The plastic deformation process may be useful in the effect of aging process and helpful to improve the mechanical properties of Al-2024 alloy. Some studies have shown that the plastic deformation process may be useful in the effect of aging process, which is helpful to improve the mechanical properties of aluminum alloy and refine the precipitated phase of alloys notably [3]. However, there are few studies available concerning the effect of the pre-deformation degree on the microstructure and precipitation kinetics.The Al-2024 alloy was melted in a LINDBERG BLUE electric furnace at 740°C, degassed for 5 minutes with Argon gas (20 psi), using a graphite propeller at 490 rpm and finally 0.33 wt% of Al-5Ti-1B as grain refiner was added. The alloys were cast into steel molds preheated at 260°C, where specimens of approximately 101.39 mm long x 12.64mm wide x 9.57 mm height were obtained. Later these specimens were machined to obtain samples of approximately 97 mm long x 10 mm wide x 8mm high. Subsequently, hot rolling (pre-deformation) at ≈460 °C was carried out to reduce the thickness of the sample 50% and erase the as-cast microstructure. Subsequently, solution treatments at 495°C for 3, 5 and 7h were done in a LINDBERG-BLUE electric furnace followed by a quenching in water at 60°C. Thereafter, a cold rolling was carried out to reduce the thickness of the sample 5 and 15%. Finally, samples were cut approximately 19.46 mm long to be treated by aging in a FELISA furnace at 195°C for different periods of time. The microstructural evolution was studied by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).The effect of homogenization-solubilization treatment time (3, 5 and 7h) on microstructure in Al-2024 alloy is shown by SEM micrographs in Fig. 1. It is observed from the results that in all homogenizationsolubilization treatment times, segregation decrease compared with as-cast conditions, but samples treated for 5 and 7h shown lower segregation.The Fig. 2 shows HRB and HV harness results as a function of aging time in the 2024 alloy, after 5 (a) and 15% (b) cold-working, additionally, the reference sample value is included. It is observed as the hardness in cold-working samples is greater than the reference samples. It is observed a direct effect of cold-working in hardness, high deformation -high hardness. Additionally, the cold-working affects the precipit...