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Aluminum oxide nanopowder has been fabricated and characterized successfully to improve the properties of friction stir welded aluminum/titanium joints, which pose a great challenge due to the great difference in mechanical properties. Intermetallic compounds (IMCs) of large sizes formed at the welding interface are a significant problem that deteriorates joint strength due to the uncontrollable thermal effect generated in the joint. Therefore, friction stir processing was integrated with friction stir welding, in which a dissimilar lap joint of AA6061-T6 and Ti6Al4V was reinforced with γ-Al 2 O 3 nanoparticles of about 8 nm in diameter. First, several attempts were conducted to determine the most effective parameters in the welding process of the aluminum/titanium reinforced joint and then the effects of γ-Al 2 O 3 nanopowder on microstructure, mechanical properties, and weldability were analyzed and compared to a welded joint without reinforcing powder. Sound joints have been successfully produced using welding speed of 25 mm/min, and tool rotational speed of 600 rpm. Lap shear fracture load and displacement of the Al/Ti joint increased from 3.5 KN and 1.25 mm to 3.7 KN and 2.45 mm, respectively, while the hardness of the reinforced joint increased from 384 HV to 391 HV at the Al/Ti weld interface with a remarkable improvement at the Al and Ti sides. • Al/Ti FSWed joint was reinforced with aluminum oxide nanoparticles (γ-Al 2 O 3 NPs). • The effect of γ-Al 2 O 3 NPs on microstructure, mechanical properties, and strengthening of the joints was discussed. • γ-Al 2 O 3 NPs refine the grains at Al/Ti interface and reduce the thickness of Al/Ti intermetallic compounds. • γ-Al 2 O 3 NPs improve the tensile strenght, ductility, and hardness of the Al/Ti joint. [ABSTRACT FROM AUTHOR]

The improved wear and corrosion resistance of gray cast iron (GCI) with enhanced mechanical properties is a proven stepping stone towards the longevity of its versatile industrial applications. In this article, we have tailored the microstructural properties of GCI by alloying it with titanium (Ti) and tungsten (W) additives, which resulted in improved mechanical, wear, and corrosion resistance. The results also show the nucleation of the B-, D-, and E-type graphite flakes with the A-type graphite flake in the alloyed GCI microstructure. Additionally, the alloyed microstructure demonstrated that the ratio of the pearlite volume percentage to the ferrite volume percentage was improved from 67/33 to 87/13, whereas a reduction in the maximum graphite length and average grain size from 356 ± 31 µm to 297 ± 16 µm and 378 ± 18 µm to 349 ± 19 µm was detected. Consequently, it improved the mechanical properties and wear and corrosion resistance of alloyed GCI. A significant improvement in Brinell hardness, yield strength, and tensile strength of the modified microstructure from 213 ± 7 BHN to 272 ± 8 BHN, 260 ± 3 MPa to 310 ± 2 MPa, and 346 ± 12 MPa to 375 ± 7 MPa was achieved, respectively. The substantial reduction in the wear rate of alloyed GCI from 8.49 × 10−3 mm3/N.m to 1.59 × 10−3 mm3/N.m resulted in the upgradation of the surface roughness quality from 297.625 nm to 192.553 nm. Due to the increase in the corrosion potential from −0.5832 V to −0.4813 V, the impedance of the alloyed GCI was increased from 1545 Ohm·cm2 to 2290 Ohm·cm2. On the basis of the achieved experimental results, it is suggested that the reliability of alloyed GCI based on experimentally validated microstructural compositions can be ensured during the operation of plants and components in a severe wear and corrosive environment. It can be predicted that the proposed alloyed GCI components are capable of preventing the premature failure of high-tech components susceptible to a wear and corrosion environment. [ABSTRACT FROM AUTHOR]

Sheet metals such as titanium alloys, steel alloys, and aluminum alloys are significant materials due to their importance among everyday life products as well as high-strength applications in aircraft, ships, automobiles, construction, military, and marine purposes. Recently, laser cutting is one of the best and fastest non-conventional methods to cut sheet metals, so it is necessary to understand how laser cutting parameters affect cutting quality. A comprehensive review was presented to investigate how laser cutting parameters affect the cut surface and kerf quality and which parameters affect cutting quality the most. An overview of the advantages of laser cutting when compared to other methods of machining was presented. In addition, a description of the laser cutting method and the different sources of laser were presented with clearing the range of thicknesses of the cut material for each source and their advantages. Also, a description of the properties and the applications of the studied materials were discussed. The performance parameters ofcutting were illustrated in detail by graphs and equations. The research analysis and discussion were discussed in such organized details by tables and graphs which show the full classification of the studied papers. It was found that the best conditions to obtain low surface roughness, small HAZ width, small kerf width, and small kerf angle are using low laser power, high cutting speed, medium gas pressure, high standoff distance, medium pulse frequency, medium pulse width, small nozzle diameter, small thickness, and nitrogen as an assist gas. [ABSTRACT FROM AUTHOR]

Titanium alloys, especially Ti–6Al–4 V alloy, are significant materials because of their superior mechanical and chemical properties. They are used in most high-strength and elevated temperature applications, such as aircraft, ships, biomedicine, and marine applications. Recently, laser machines were used to cut a variety of sheet metals. It is critical to comprehend how laser cutting parameters influence surface and kerf quality. In this work, a 4 mm-thick Ti–6Al–4 V sheet was cut. Laser beam power, cutting velocity, and assist gas pressure were used as cutting parameters, while surface roughness, kerf width, taper angle, and dross height were measured to determine which parameter has the greatest influence on the cutting quality. It was found that laser power of 3 kW, cutting velocity of 2000 mm/min, and assist gas pressure of 8 bar were the optimized parameters to achieve the minimum surface roughness value of 2.34 ± 0.12 µm and the minimum dross value of 0.270 mm due to the high velocity. The minimum value of kerf width was found to be 0.774 ± 0.016 mm at upper surface and 0.408 ± 0.039 mm at lower surface of cut at cutting conditions of Pu = 2.5 kW, V = 1500 mm/min, and assist gas pressure of 10 bar. The minimum value of kerf taper was found to be 1.89 ± 0.61° at cutting conditions of Pu = 2 kW, V = 1500 mm/min, and assist gas pressure of 8 bar. [ABSTRACT FROM AUTHOR]

[Display omitted] COVID-19 outbreak has become a global pandemic that affected more than 200 countries. Predicting the epidemiological behavior of this outbreak has a vital role to prevent its spreading. In this study, long short-term memory (LSTM) network as a robust deep learning model is proposed to forecast the number of total confirmed cases, total recovered cases, and total deaths in Saudi Arabia. The model was trained using the official reported data. The optimal values of the model's parameters that maximize the forecasting accuracy were determined. The forecasting accuracy of the model was assessed using seven statistical assessment criteria, namely, root mean square error (RMSE), coefficient of determination (R2), mean absolute error (MAE), efficiency coefficient (EC), overall index (OI), coefficient of variation (COV), and coefficient of residual mass (CRM). A reasonable forecasting accuracy was obtained. The forecasting accuracy of the suggested model is compared with two other models. The first is a statistical based model called autoregressive integrated moving average (ARIMA). The second is an artificial intelligence based model called nonlinear autoregressive artificial neural networks (NARANN). Finally, the proposed LSTM model was applied to forecast the total number of confirmed cases as well as deaths in six different countries; Brazil, India, Saudi Arabia, South Africa, Spain, and USA. These countries have different epidemic trends as they apply different polices and have different age structure, weather, and culture. The social distancing and protection measures applied in different countries are assumed to be maintained during the forecasting period. The obtained results may help policymakers to control the disease and to put strategic plans to organize Hajj and the closure periods of the schools and universities. [ABSTRACT FROM AUTHOR]

The flow behavior of sand particles has been examined by computational fluid dynamics (CFD) and experimental validations in sand shooting process. To avoid over-estimating the drag force between gas and solid phases, the energy minimization multiscale model(EMMS)has been incorporated. An applicable value of grid size is determined by grid dependency study. Three specularity coefficients are simulated to get an insight into the influence on the flow hydrodynamics of sand particles. The specularity coefficient affects tangential velocity and volume distribution of sand particles. No slip wall boundary condition is in better agreement with experimental data. With validation of sand shooting experiment, agreement is achieved between experiment images and simulation results. A comparison between EMMS drag model and Gidaspow model has been discussed in terms of simulating particles flow behavior with different particle diameters. The EMMS drag model has an accuracy prediction especially for smaller particles and dense flow. Unlabelled Image • The EMMS-based drag model is introduced in sand shooting simulation. • Validation of simulation by high-speed camera recording experiments is illustrated. • Specularity coefficient affects sand particles flow behaviors. • EMMS model get a well-prediction for smaller particles and dense flow. [ABSTRACT FROM AUTHOR]

• The embrittlement X factor for weld metal is 45, which is three times more than the recommended value (≤15). • It is apprehended that the fractured metal part could be susceptible to temper embrittlement. • The Charpy impact energy absorbed by the fractured metal is 13 J, which is lower than impact energy absorbed by the base metal 300 J. • The scanning electron microscopy demonstrated intergranular crack propagation, discontinuous cracking along grain boundaries, and blunted cracks at grain interiors. • The fractography is performed on the fracture surface of the impact test specimens and it indicated heavily cavitated intergranular facets along the grain boundaries and deep secondary cracks on the fracture surface. • These findings suggested that the severe cracking observed in the fire tube at the U-bend is likely due to temper embrittlement (TE) induced by exposure of the fire tube material to elevated temperatures. Overheating, corrosive degradation, hydrogen embrittlement, creep, erosion, and corrosion are the cause of most failure problems in fire tubes. Herein, we have evaluated the macrostructural, microstructural, and mechanical properties at welded U-bend of the fractured fire tube to analyze the failure of the SA 387 grade 22 steel heater treater fire tube that has been under continuous use for 18 years at an oil refinery. We have found that the embrittlement factor at U-bend proved to be the most significant factor in its failure. The embrittlement X factor for weld metal is 45, which is three times more than the recommended value (≤15). It is apprehended that the fractured metal part could be susceptible to temper embrittlement. There is a significant higher hardness value of weld metal as compared to base metal, which is due to metallic phase transition at high temperature. The Charpy impact energy absorbed by the fractured metal is 13 J, which is lower than impact energy absorbed by the base metal 300 J. The macroscopic examination reveals that the crack initiated on the emulsion side and propagated radially in welded U-bend before extending further into the base metal in the axial direction. The scanning electron microscopy demonstrated intergranular crack propagation, discontinuous cracking along grain boundaries, and blunted cracks at grain interiors. The fractography is performed on the fracture surface of the impact test specimens, and it indicated heavily cavitated intergranular facets along the grain boundaries and deep secondary cracks on the fracture surface. Energy disperse spectroscopy identified the carbides formation at the U-bend cracking parts, which counter confirm the microstructural phase transition. These findings suggested that the severe cracking observed in the fire tube at the U-bend is likely due to temper embrittlement (TE) induced by exposure of the fire tube material to elevated temperatures. [ABSTRACT FROM AUTHOR]