Journal of advanced materials and processing
Volume:7 Issue: 3, Summer 2019

In this study, nitrogen and cerium co-doped titanium dioxide nanoparticles were prepared by the sol-gel method and were calcined in air at550 °C for 2 hours. Then, the surface glassy carbon electrode was modified and coated with synthesized nanoparticles. The crystalline structure of the nanoparticles was characterized by X-ray diffraction (XRD). The topography, surface roughness and particle size distribution of the coatings were investigated by atomic force microscopy (AFM). Photoelectric properties such as the changes of the absorption edges and band gap values of the nanoparticles were studied by diffuse reflectance spectra (DRS). The hydrophilic property of the coatings was also measured by a contact angle device. In all of the analyses, the effect of nitrogen doping amount on the characteristics of N, Ce co-doped titania samples was investigated. According to the results, the band gap of the co-doped titania samples relative to that of pure titania has been decreased (from  3.21 eV to  2.78 eV) and their surface hydrophilicity has been improved (from 1.01 (deg.min-1) to 1.60 (deg.min-1)). Among the samples the co-doped titania contains the ratio of Ce/Ti: 1% and N/Ti: 0.25%, has the highest amount of anatase phase ( 93.1%), the lowest agglomeration at the surface, the smallest band gap energy ( 2.78 eV) and the highest photo-induced super-hydrophilicity (hydrophilizing rate: 1.60 (deg.min-1)).

Deep sub-zero treatment is a complementary operation performed on all types of tool steels, carbonized and high-speed steels to improve wear resistance and hardness. Among these tool steels, H13 is a hot work tool steel that have an extended application in industry as a hot deforming tool. This paper investigates the wear behavior of deep cryogenic treated H13 hot work steel at operating temperature. Two quench-tempered and quench-subzero-tempered samples are compared. The microstructures of the specimens were determined by scanning electron microscopy, and the structures were determined by X-ray diffraction. Vickers hardness used for determining hardness after each treatment. The wear test was carried out at 250°C (mold temperature on forging of copper base alloys). Finally, the wear surface was examined by scanning electron microscope equipped with EDS analyzer. The results show that the highest hardness was in quench-subzero-tempered condition which is about 26% higher than the quench-tempered in oil conditions. This is due to the formation of fine, dispersed and uniform precipitates and higher martensite percentage in quench-subzero-tempered sample compared to quench-tempered sample. Quench-subzero-temper operation reduced the residual austenite percentage by 10% and improved the wear properties by 36% at 250° C. Examination of wear surfaces indicates the presence of oxidized surfaces adhered to the wear surface in the form of abrasive particles. These oxide levels were lower in quench-subzero-tempered sample than quench-tempered sample.

Due to the low quality of domestic coking coal, as well as increased restrictions on international trade of importing coking coal from abroad, Iranian steel industry have been faced with the serious challenges of supplying coke as the major source of blast furnaces energy; on the other hand, the vast sources of domestic natural gas and pulverized coal have made it possible to replace coke with these sources of energy in the blast furnaces. High differences in price of coke with natural gas and pulverized coal, the influence of replacing complexity on the cost of ferrous raw materials, coke, and energy consumption, blast furnace productivity, technical constraints, and carbon dioxide emissions level are the main reasons for conducting this research. In this study, a nonlinear optimization model was developed to determine the profit of hot metal in blast furnace. Compared to previous studies, optimal decision making on the supply and replacement of raw materials and energy, along with new constraints were analyzed. The proposed model was implemented in MATLAB and validated by using data of Esfahan Steel Company. The results revealed that the research model can decrease coke consumption by 26% and is strongly effective in attaining economic benefits.

In the present study, the effects of magnesium on the microstructural characteristics and stress-rupture properties of Hastelloy X superalloy were investigated. In this regard, four alloys with different amounts of Magnesium (0, 17, 33, 47 ppm) were cast via the vacuum induction melting and then purified via the electro slag remelting. Microstructural observations were carried out through optical and scanning electron microscopes and phase analysis was performed by x-ray diffraction. The stress rupture test was carried out at 815 °C/130 MPa. The results showed an almost significant effect of Magnesium on decreasing grain size and sulfur content and increasing M6C carbides volume fraction. Magnesium changed the morphology of carbides from course and continuous to finely divided one. Mg segregated at the grain and carbide boundary, decrease the lattice parameters of matrix and change the composition of M6C. Magnesium increased the rupture life by 46%. The most important causes for improving the rupture life of the Hastelloy X in the presence of Magnesium are the increasing carbides volume fraction, improving its morphology and decreasing sulfur content.

The aim of this study is to find the effect of the Parallel Tubular Channel Angular Pressing (PTCAP) technic as a Severe Plastic Deformation (SPD) method on microstructure and mechanical properties of as-extruded AZ61 magnesium alloy. The main reason to accomplish this research is to achieve certainty while this process could enhance the mechanical characteristics of magnesium alloy. To this end, the initial material was processed for one, two and three passes at 350 °C. Afterward, the microstructure was studied by optical microscope (OM) and scanning electron microscope (SEM). Next, to verify the mechanical properties alterations, tensile tests were performed for each specimen. Then, in order to investigate stress and strain status during the process, process simulations were fulfilled by employing the software Abaqus. Microstructure investigations revealed the fact that after just one pass, great grain refinement occurred within the material. Al4Mn as a secondary phase was noted for 1-pass, 2-pass and 3-pass processed specimens via scanning electron microscopy images and Energy Dispersive X-ray Spectroscopy (EDS) patterns. Finite elements method results illustrated the highest value of stress for the second half-cycle of the third pass. The maximum amount of strain tolerated by material belonged to the second half-cycles of the second and third pass. Finally, it could be reasoned that the best properties achieved for the 2-pass processed specimen possessed the best strength and deformability values.