Papers by Keyword: Microstructure

Abstract: Nickel-based coatings are a vital technology in industrial applications, offering protection to metallic objects against high temperatures, wear, corrosion, and erosion. The current research work examines the deposition of NiCrBSi powder in Stainless steel (AISI SS 304) using the high-velocity oxy-fuel (HVOF) thermal spray coating technique. The effects of HVOF-deposited NiCrBSi coatings on the microstructure, morphology, and mechanical and physical properties of the coated stainless steel. Microstructural and morphological analyses were performed using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD) to characterize the coating. The coatings were systematically assessed for surface roughness, deposition efficiency, coating thickness, and porosity. Adhesion strength was measured using a pull-off adhesion tester to ensure robust bonding. The results demonstrate that HVOF-sprayed NiCrBSi coatings possess low porosity (2-3%), strong adhesion (45–55 MPa), and increased hardness, making them highly suitable for high-temperature, anti-wear applications, with improved durability and performance under harsh operating conditions.

Abstract: Mg-Al-Zn alloy, an Mg alloy having Al and Zn as the major constituents, is exceptionally lightweight and has potential to become an essential component of modern engineering applications and healthcare systems. This paper presents valuable insights to the friction stir processing (FSP) applied to Mg-Al-Zn alloy in dry conditions. FSP induced extreme plastic deformation in the metal alloy which causes substantial microstructural alterations. These changes were investigated using optical microscope. Microstructural evaluation of FSP-processed zone indicated that average grain diameter of the FSP-processed zone increased in proportion to tool rotating speed. This is attributed to the frictional zone's degree of plastic deformation. In alignment with results obtained from optical microscopy, morphological study conducted using scanning electron microscope (SEM) also demonstrated the synthesis of refined grains. In addition, the study includes evaluation of the FSP-processed alloy's micro-hardness and tensile characteristics in contrast to the base (unprocessed) alloy.

Abstract: ZnO thin films were deposited on borosilicate glass substrates by confocal radio frequency (RF) magnetron sputtering and subsequently annealed in air at 300 °C and 500 °C for 60 min. The influence of thermal treatment on the structural, morphological, optical, and electrical properties was systematically investigated. X-ray diffraction (XRD) confirmed the formation of a hexagonal wurtzite phase with a pronounced (002) preferential orientation. Rietveld refinement analysis revealed that annealing led to a decrease in the lattice parameter c from 5.344 Å to 5.220 Å, an increase in crystallite size from 9.3 nm to 34.1 nm, and a reduction in microstrain from 0.0265 to 0.0027. Raman spectroscopy exhibited a sharper E₂^high mode at 438 cm^-1 and a suppressed defect-related A₁(LO) mode (583 cm^-1), evidencing enhanced crystallinity and defect passivation. Scanning electron microscopy (SEM) observations revealed grain coalescence and densification with increasing annealing temperature. The average optical transmittance improved from 70.8% to 82.2%, accompanied by a slight widening of the optical band gap from 3.22 eV to 3.27 eV. Hall measurements indicated a marked decrease in resistivity from 2.7 × 10^-2 Ω·cm to 5 × 10^-3 Ω·cm, yielding a maximum figure of merit of 1.68 × 10^-3 Ω^-1 at 500 °C. Overall, post-deposition annealing is shown to significantly enhance crystallinity, reduce structural defects, and improve the optoelectronic performance of ZnO thin films, confirming their suitability for transparent electronics and photovoltaic applications.

Abstract: This study investigates how heat treatment affects the mechanical properties and microstructure of extruded AA2017 aluminum alloy. Quenching (icy water vs. liquid nitrogen) and tempering (T6: 120–160°C; T7: 240°C) significantly alter hardness, tensile strength, and fatigue life. T6 promotes fine, coherent precipitates, enhancing strength and fatigue resistance, while T7 leads to over-aging and property degradation [X]. Icy water quenching improves fatigue life over liquid nitrogen by refining precipitates [Y]. Microstructural analysis reveals elastic adaptation (T6) and plastic shakedown (T7) as fatigue stabilization mechanisms, with fracture modes shifting from ductile (T6) to mixed ductile-brittle (T7) [Z]. These results optimize heat treatment for AA2017 in high-strength, fatigue-critical applications.

Abstract: This study assesses the impact of heat treatment on the microstructure and mechanical properties of AlSi10Mg alloy produced using the L-PBF method. The research compares the mechanical properties and microstructure of samples subjected to direct aging (heat treatment at 170 °C/2 h) and stress relief annealing (at 240 °C/2 h), which is below the temperature for silicon network decomposition. These results are then compared with the as-built state (without any heat treatment) after printing, serving as a reference. Tensile and hardness tests were used to determine the mechanical properties, while electron microscopy was employed to analyze the microstructure. The findings indicate that direct aging led to an increase in yield strength, tensile strength and hardness compared to the as-built state. In contrast, samples treated with stress-relief annealing exhibited comparable yield strength to the as-built state, but significantly lower tensile strength and reduced hardness. Notably, contrary to expectations, the ductility did not increase with decreasing strength and hardness; instead, it decreased.

Abstract: In this work, a TiNbCr alloy is proposed for solid-state hydrogen storage applications. The design of the alloy is based on the Hume-Rothery rules and the thermodynamic parameters ΔH_mix and Ω, while the alloy was conceived as single-phase with a BCC lattice. Samples were synthesized from alloy powder using additive technology and the DED method. The prepared samples were printed with different parameters and their structure and phase composition were subsequently analyzed. The possible influence of these printing parameters on the properties of hydrogen storage alloys is discussed.

Abstract: Aluminum alloy 6082 is known for its use in the manufacture of structures that require welding interventions, high mechanical properties, resistance to pressure and corrosion, such as: boilers, truck structures, bicycles and motor boats. The recent research, regarding the cavitation resistance of the this alloy structure, shows a poor behavior of the semi-finished structure and somewhat improved by artificial aging volumetric heat treatment regimes. On the line of increasing the resistance of the this alloy structure, to the erosive demands of cavitation, they sign up of the rechearch results of the this paper, regarding the behavior and resistance of the vibratory cavitation of the aluminum alloy 6082 structure , obtained by WIG remelting. Comparing with the results obtained on the structures in the semi-finished state and through volume thermal treatments of artificial aging state, using the established parameters, recommended by the ASTM G32-2016 norms, a significant increase in the resistance to cyclic cavitation stresses is found, as a result of the increase in the surface hardness value. The novelty of the work consists in motivating the use of the remelting procedure of the surface structure of aluminum alloy 6082, through WIG remelting in order to increase the surface hardness, with a direct effect on increasing this structure resistance to the cyclical fatigue stresses of shock waves and microjets developed through the hydrodynamic mechanism of cavitation.

Abstract: The paper presents the results of the behavior and resistance to the erosion by cavitation of the 2017 A aluminium alloy structure, obtained by the WIG remelted method. The research is in step with the new directions of study and aims to extend the aluminum alloy 2017 A to the manufacture of parts that work in the cavitation regime, such as: pistons and valves of thermal engines, respectively various pump rotors or motor boat propellers. The analysis performed on the basis of the specific curves, constructed according to the indications of the ASTM G32-2016 normas, shows that structure, obtained by the WIG remelting, confers a constant behavior to the cyclic stresses of microjets generated by the hydrodynamics of the vibratory cavitation. The comparison of the results, based on the specific parameters, used in the laboratory and indicated by the ASTM G32-2016 norms shows a resistance to cavitation erosion, clearly superior to the semi-finished structure and those obtained by artificial aging heat treatment at 1800C and 120 0C, with duration of one hour.

Abstract: Lightweight steel structural systems like trusses or built-up beams, made of thin gage steel elements, are highly efficient, with ease of handling and construction. Self-drilling screws are commonly used for connecting thin-walled elements, but the time and manpower required for numerous connections necessitate an improved solution. One possible solution is to use welding technology, but the conventional methods are not suitable for joining thin sheets. Manufacturing defect-free, mechanically sound welding joints remains challenging due to defects like porosity and undesired microstructural phases in the heat-affected (HAZ) and fusion zones (FZ). Conventional welding processes increase heat input, causing difficult challenges. Brazing, a relatively new joining process, offers the advantages of lower heat input for thin and zinc-coated steel sheets. Therefore, the paper aims to present the effect of MIG brazing parameters on the macro-and microstructural properties of Cu-Al-based weld seams manufactured for joining thin sheets with thickens in the range of 0.8-2 mm. The weld seams were manually fabricated using a MEGAPULS FOCUS 330 compact equipped with TBI XP 363S/4m welding torch, focusing on optimal welding regimes. The macro-and microstructures of the joints were evaluated along with the mechanical properties in terms of hardness, confirming that MIG brazing is a promising method for manufacturing lightweight steel structural systems.

Abstract: Depending on the collecting methods, coal combustion by-products are usually divided into fly ash, bottom ash, and flue gas desulfurization product. Because they are a hazardous dust source, they are often stored underwater in ponds or lagoons and are called pond ash. In this investigation, the pond ashes from Ulaanbaatar's 4^th TPS (thermal power station) and Erdenet’s TPS were characterized by XRF, XRD, BET, PSD, SEM and TEM. The pond ash of the 4^th TPS contains more than 20% calcium oxide, while Erdenet’s TPS contains around 4% calcium oxide. PSD of the 4^th TPS shows a bimodule distribution with a maximum of 36 and 260 mm, while Erdenet's pond ash shows an unimodal distribution with a maximum of 74 mm. The main crystalline compounds of the 4^th TPS pond ash were quartz, calcite, hematite, albite, while in the Erdenet pond ash were quartz, mullite, magnetite, and calcite. The mineralogical composition of the pond ashes depends on the used coal type, the power plant’s working principle and the duration of time inside the ash pond. The alkali-activated binder prepared from these pond ashes demonstrated a weak compressive strength of around 1.5-2.5 MPa after 7 days. Notably, the high-calcium pond ash-based alkali-activated paste exhibited slightly higher mechanical properties than the low-calcium pond ash-based paste. The weak mechanical properties of the pond ash-based alkali-activated materials are related to both pond ashes’ porous and high-surface microstructure. High calcium pond ashes could exhibit a partial calcium silicate formation reaction, which is the reason for the higher mechanical properties than low calcium pond ash-based alkali-activated pastes. Furthermore, a brief mechanical activation of these pond ashes for 20 min slightly improved their mechanical properties, reaching up to 3.75 MPa.