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Low carbon steel sheets are subjected to severe plastic deformation (SPD) via constrained groove pressing (CGP) up to five passes. As a result of this process, strain magnitude up to 5?8 is imposed to the sheets, which leads to grain size of 225 nm. These nanostructured steel sheets, due to their high dislocation density and ultrafine microstructure, are very sensitive to heating. In the present study, recovery, recrystallisation and ferrite to austenite phase transformation phenomena for the SPD steel are investigated using differential scanning calorimetry method. The results show that with increasing the strain in steel sheets, the deformed stored energy (released through recovery and... 

However, there are many works on annealing process of SPDed non-ferrous metals, there are limit works on annealing process of SPDed low carbon steel. Therefore, in this study the annealing responses after constrained groove pressing (CGP) of low carbon steel sheets have been investigated. The sheets are subjected to severe plastic deformation at room temperature by CGP method up to three passes. Nano-structured low carbon steel sheets produced by severe plastic deformation are annealed at temperature range of 100-600 °C for 20. min. The changes of their microstructures after deformation and annealing are studied by optical microscopy. The effects of large strain and annealing temperature on... 

In this research, constrained groove pressing (CGP) technique is used for imposing severe plastic deformation (SPD) on the low carbon steel sheets. Using transmission electron microscopy (TEM), X-ray diffraction (XRD) and optical microscopy, the microstructural characteristics of produced sheets are investigated. The results show that CGP process can effectively refine the coarse-grained structure to an ultrafine grain range. Dislocation densities of the ultrafine grained low carbon steel sheets are quantitatively calculated and it is found that the CGP can effectively enhance the dislocation density of the sheets. Measurements of their electrical resistivity values show that microstructure... 

In order to investigate the evolution of microstructure and flow stress during non-isothermal annealing, aluminum samples were subjected to strain magnitudes of 1, 2 and 3 by performing 2, 4 and 6 passes of multi-directional forging. Then, the samples were non-isothermally annealed up to 150, 200, 250, 300 and 350 °C. The evolution of dislocation density and flow stress was studied via modeling of deformation and annealing stages. It was found that 2, 4 and 6 passes multi-directionally forged samples show thermal stability up to temperatures of 250, 250 and 300 °C, respectively. Modeling results and experimental data were compared and a reasonable agreement was observed. It was noticed that... 

A simple procedure for the synthesis of dipyrazolo[1,5]diazocine-3,8-diones was developed via the one-pot reaction of 3-aminopyrazolone with substituted benzaldehydes in the presence of catalytic p-toluenesulfonic acid (PTSA). © 2018 Elsevier Ltd  

Highly cold worked (HCW) low carbon steel sheets with cellular structure in the range of 200 to 300 nm are fabricated via constrained groove pressing process. Joining of the sheets is carried out by resistance spot welding process at different welding currents and times. Thereafter, failure behavior of these welded samples during tensile-shear test is investigated. Considered concepts include; failure load, fusion zone size, failure mode, ultimate shear stress, failure absorbed energy, and fracture surface. The results show that HCW low carbon steel spot welds have higher failure peak load with respect to the as-received one at different welding currents and times. Also, current limits for... 

Constrained groove pressing as a severe plastic deformation method is utilized to produce ultra-fine grained low carbon steel sheets. The ultra-fine grained sheets are joined via resistance spot welding process and the characteristics of spot welds are investigated. Resistance spot welding process is optimized for welding of the sheets with different severe deformations and their results are compared with those of as-received samples. The effects of failure mode and expulsion on the performance of ultra-fine grained sheet spot welds have been investigated in the present paper and the welding current and time of resistance spot welding process according to these subjects are optimized.... 

The welding of nanostructured low carbon steel sheets produced by severe plastic deformation (SPD) has been considered in the present paper. Constrained groove pressing (CGP) method is used for imposing the severe plastic deformation to the steel sheets as a large pre-strain. The SPDed sheets are joined using resistance spot welding (RSW) process. The results show that severe plastic deformation can effectively increase the electrical resistivity of steel sheets; therefore it can affect the microstructure and mechanical properties of spot welds. Microstructure and mechanical properties of fusion zone, heat affected zone (HAZ), recrystallized zone and base metal of SPDed sheets are... 

The need for simplified physical models representing frequency dependent soil impedances has been the motivation behind many researches throughout history. Generally, such models are generated to capture impedance functions in a wide range of excitation frequencies, which leads to relatively complex models. That is while there is just a limited range of frequencies that really influence the response of the structure. Here, a new methodology based on the response-matching concept is proposed, which can lead to the development of simpler discrete models. The idea is then used to upgrade an existing simple model of surface foundations to the case of embedded foundations. The applicability of... 

In this study a severe plastic deformation method called constrained groove pressing (CGP) is used for imposing a high magnitude of strain into the low carbon steel sheets. Microstructural changes during process are examined by X-ray diffraction and optical observations. The grain size evolution during severe plastic deformation is studied using Williamson-Hall analysis on XRD pattern of the deformed samples. In effective strain of 4.64, ferrite grains with a submicron size of 200-300nm are achieved. The results show that constrained groove pressing can effectively refine the coarse-grained structure to an ultra fine grain range. Mechanical properties changes due to microstructure evolution... 

We studied the microstructure and mechanical characteristics of spot welded specimens, fabricated from low carbon steel sheets with different microstructures. Both ultra-fine grained (UFG) steel sheet and coarse grained (CG) steel sheet were used. The refined microstructure of the UFG steel has been produced by severe plastic deformation (SPD) using the constrained groove pressing (CGP) method. The grain size of the base metals was approximately 260. nm and 30. μm in diameter, respectively, in the UFG and CG steels. Examining the microstructure of a cross section cut through the spot weld reveals a similar grain size and phase distribution in the nugget on both the sides of the initial... 

Solid-state joining of powder-metallurgy processed (P/M) Al–2 vol% Al2O3 (15 nm) nanocomposite by friction stir welding (FSW) was studied. The nanocomposite was prepared via high-energy mechanical milling followed by hot consolidation processes. The microstructure, mechanical properties and fracture behavior of the welds were evaluated and compared with FSWed wrought 1050 aluminum sheets (WAS). We have found that unlike WAS that can processed at various FSW conditions, the working window for the solid-state joining of P/M nanocomposite is narrow and only feasible at relatively high heating inputs. Microstructural studies showed the formation of melted zones with high hardness at the... 

A new modification of constrained groove pressing (CGP) process named as constrained groove pressing-cross route (CGP-CR) was suggested for severe plastic deformation (SPD) of sheet form metals with great potential for fabricating high strength nanostructured sheets. This process is based on the conventional CGP process including some modifications. One pass of this process includes eight stages (four corrugation and four flattening) and involves 90° cross-rotation between each two stages. As a result of each CGP-CR pass, a strain magnitude of ∼2.32 is imparted to the sample. To simulate the process, finite element modeling (FEM) was carried out using three-dimensional finite element... 

The effect of α-Al 2O 3 seeds and MgO on the densification behavior and microstructure of the nanocrystalline γ-Al 2O 3 powder was investigated. The required α-Al 2O 3 seeds were produced by 'autogenous seeding' where the seeds were obtained by calcination of the initial nanosized γ-Al 2O 3 powders above its transformation temperature and incorporated into γ-Al 2O 3 matrix. The seeds were characterized by means of laser particle size analyzer, X-ray diffraction, and Brunauer-Emmett-Teller surface analyzer. The simultaneous influence of α-Al 2O 3 seeds and MgO on γ-Al 2O 3 behavior was evaluated by differential thermal analysis, densitometry, and electron microscopy. The results showed that... 

A modified method of severe plastic defomation (SPD) entitled constrained groove pressing-cross route (CGP-CR) was introduced for imposing a high magnitude of equivalent strain of about 2.32 per pass on the sheet form samples. The major benefit of this improved route compared to previous common route was the more homogeneity of strain in the rolling (RD) and transverse (TD) directions of sheets. In this study, low carbon steel samples were used for examination of evolutions in microstructure and mechanical properties during SPD via CGP-CR process. Mechanical properties improvement were measured by tensile and macro hardness tests. The results indicate that CGP-CR process can effectively... 

Aluminum matrix nanocomposites were fabricated via friction stir processing of an Al–Mg alloy with pre-inserted TiO2 nanoparticles at different volume fractions of 3%, 5% and 6%. The nanocomposites were annealed at 300–500 °C for 1–5 h in air to study the effect of annealing on the microstructural changes and mechanical properties. Microstructural studies by scanning and transmission electron microscopy showed that new phases were formed during friction stir processing due to chemical reactions at the interface of TiO2 with the aluminum matrix alloy. Reactive annealing completed the solid-state reactions, which led to a significant improvement in the ductility of the nanocomposites (more... 

Friction stir processing (FSP) is a solid state route with a capacity of preparing fine grained nanocomposites from metal sheets. In this work, we employed this process to finely distribute TiO2 nanoparticles throughout an Al–Mg alloy, aiming to enhance mechanical properties. Titanium dioxide particles (30 nm) were preplaced into grooves machined in the middle of the aluminium alloy sheet and multipass FSP was afforded. This process refined the grain structure of the aluminium alloy, distributed the hard nanoparticles in the matrix and promoted solid state chemical reactions at the interfaces of the metal/ceramic particles. Detailed optical and electron microscopic studies showed that the... 

A new and efficient method has been developed for the synthesis of 5,7-diaryl-5,6,7,8-tetrahydropyrimido[4,5-d]pyrimidine-2,4-dione derivatives by cyclization of 6-aminouracils with N,N′-bis(arylmethylidene)arylmethanes (diimines). The products were formed in good yields and with very good anti-diastereoselectivity. The best yields were obtained when p-toluenesulfonic acid (PTSA) was used as the catalyst. The solvent also played an important role in the optimization. An amino-substituted 6-aminouracil and a corresponding sulfur analog could be successfully employed. In addition, various diimines, electron rich and neutral, could be successfully employed. The products are of relevance as... 

Achieving a high speed, unidirectional water flow through carbon nanotubes (CNTs) is a key factor in designing novel nanofluidic devices. In this study, utilizing molecular dynamics (MD) simulations, we propose a novel nanoscale water pump for directed water transportation using charged rotating CNTs. Two basic conditions for stable water flow, including thermodynamic nonequilibrium and spatial asymmetry, are provided by introducing partial charges on carbon atoms of the channel with asymmetric patterns and its rotation, respectively. We demonstrate that the performance of the water pump is proportional to the gradient of a linear charge distribution and angular velocity of the rotation. Our... 

There are many engineering applications in which composite materials are required to satisfy two or more criteria regarding physical and mechanical properties. In this article, Al-matrix nanocomposites reinforced with different volume fractions of SiC nanoparticles (~ 50 nm; up to 6%) were processed by powder metallurgy (P/M) routes through mechanical milling and hot consolidation techniques. Microstructural studies showed that nano-metric Al2O3 particles with a size of ~ 20 nm and volume fraction of ~ 2% were formed and distributed in the metal matrix, owing to the surface oxides breaking. Microstructural analysis also revealed that the size of cellular structure and the density of...