Journal of advanced materials and processing
Volume:8 Issue: 1, Winter 2020

Mechanical properties optimization of weldment such as tensile strength, microhardness and impact toughness are of prime importance in welding technology. The main aim of this research is to investigate the microstructural evolutions and also optimization of tensile strength in dissimilar laser welding between Inconel 625 superalloy and AISI 430 ferritic stainless steel. It was found from the microhardness measurements that the hardness is increased form AISI 430 base metal toward Inconel 625 superalloy. This can be attributed to the inherent higher hardness of Inconel 625 and formation of very fine structure and also fine precipitations in the weld metal which are distributed uniformly. Formation of very fine structure and precipitations is due to the rapid cooling rate of the weld metal during laser welding process. Design of experiment based on the response surface method was used in order to optimize the tensile strength of the weld joints. Three process parameters i. e. pulse duration, lamping current and also travel speed were chosen as the main parameters which are considerably affecting the tensile strength of the weld joint. It was found that the lamping current has a higher impact on the tensile strength of the weld joints.

Zinc aluminate spinel structure (ZnAl2O4) was synthesized from mixtures of zinc sulfide (with sphalerite structure) and aluminum. The starting materials with different molar ratios were milled for 3 hours. The as-milled powders were heated isothermally at 800 ⁰C under an air atmosphere for one hour. The heated samples finally were washed out with diluted sulfuric acid and the remained residuals were dried at 110 ℃ for two hours. The results showed that aluminium content and the molar ratios of ZnS:Al in the starting materials have significant effect on the formation of ZnAl2O4.The as-milled results showed that although the reduction of ZnS by aluminum occurred during milling, the reaction was not completed with increasing the Al content in the starting materials. Except the molar ratio of 1:2, no signs of un-reacted Al were observed in other mixtures of ZnS-Al after milling for three hours. The XRD patterns and FT-IR spectra of the acid treated sample revealed that zinc aluminate could be synthesized from mixtures of ZnS-Al and the ZnS-Al mixture with molar ratio of 4:2 was the best among all mixtures.

The purpose of this study is to investigate and optimize parameters effective on continuous adsorption and elution and study of the corresponding breakthrough curve models for the removal of one of the main pollutants found when copper is extracted and refined. Mining has a long history of producing toxic waste so there is a heightened sense of urgency for finding ways to protect the environment especially during the initial production stages. The contaminants in water and mine wastewater are key issues in the reuse of water resources. In this study, adsorption by fixed-bed column which is usually applied for removing organic contaminants from the aqueous phase is investigated for adsorption of the antimony on a commercially available cationic resin Purolite S957 and the kinetics of adsorption is explored by establishing breakthrough and resin saturation times. Concentration and feed flow rate affect the kinetics of adsorption on a fixed-bed resin and were determined both experimentally as well as through optimization by a two-level factorial experimental design using Central Composite Design (CCD). Experiments were carried out at constant temperature and pH of 55 ℃ and 8 respectively that were determined based on optimal conditions for fixed resin content of 25 g. The breakthrough test results suggest Bohart-Adams model better fitted the experimental data compared to Thomas and Yan models with R² of 0.964. Moreover, elution of pure antimony occurred at 15 BV of elution solution and maximum concentration of antimony was achieved at about 300 mg.L- 1

Waveguides, used in electronic industries, are structures for transferring electromagnetic waves. A twist waveguide is a device used to change the polarization of waves. In this study, a process for fabricating an aluminum rectangular twist waveguide was designed and some guidelines were introduced. The preliminary profile was obtained by a forward extrusion process. In order to study the effect of strain hardening, the twisting process was studied for annealed and non-annealed samples after the extrusion process. The results revealed the necessity of annealing the samples before the twisting; otherwise, local deformation would occur. Measuring the applied torque showed that as the process progressed, the required torque for an annealed sample would increase due to work hardening, while for a non-annealed sample the torque would decrease after local deformation. Furthermore, the simulation of twisting process was performed using Deform software. No inconsistency was observed between numerical and experimental results. Moreover, investigating the cross sectional distortion showed an undesirable cross sectional distortion for the unfilled sample whereas the cross section in the sand-filled sample stayed rectangular.

Transient liquid phase (TLP) bonding of two dissimilar alloys Al 2024 and Ti-6Al-4V was carried out at 580 and 600 °C for 45 min bonding time using a 30-µm-thick pure silver (Ag) foil interlayer. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to investigate the phase structure and compositional changes across the joint region. Mechanical properties of the joints were investigated through shear strength and hardness tests. The joint formation was due to the solid-state diffusion of Ag and Cu into Al and Ti alloys, followed by eutectic formation, isothermal solidification, and formation of various intermetallic compounds such as Ag2Al, Al2Cu and Al2CuMg along the Ag/Al2024 interface. Moreover, the interdiffusion of titanium and aluminum led to the formation of Al3Ti intermetallic compounds. These types of intermetallics produced a metallurgical bond at Al 2024 interface. The study showed that the shear strength of the joint reaches a high value of 176.11 MPa obtained at the higher bonding temperature of 600 °C. It was also observed that the sample failed away from the base metal.

As reported in our previous work, Sr3Al2O6 nano powders were synthesized by a one-step solid state reaction using Al﴾NO3)3.6H2O, Sr﴾C2H3O2)2 and Sr﴾NO3)2 at 800 and 900 ̊C for 8 h. For the synthesis of Sr3MxAl2O6+δ ﴾M= Sm3+, Eu3+, Ho3+ and Yb3+) nano powders, Al﴾NO3)3.6H2O, Sr﴾NO3)2, Eu2O3, Ho2O3 and Yb2O3 were used at 800 ̊C for 8 h. In the present work, the photocatalytic performance of Sr3MxAl2O6+δ ﴾M=None, Sm3+, Eu3+, Ho3+ and Yb3+) nanomaterials were investigated for the degradation of Malachite Green (MG) water pollutant in aqueous solution under direct white visible light irradiation with the light power 40 W. The optimum conditions were obtained by design expert software for (5%) Al2O3 - (95%) Sr3Al2O6 (S1). It was found that the optimum conditions were 0.2 mL of H2O2, 20 mg of catalyst, and 40 min. The initial volume and concentration of MG solution were 150 mL and 100 ppm, respectively. It was found that Sr3Al2O6 had excellent efficiency under the optimized conditions at the presence of direct visible light irradiation. The degradation yield in the optimized conditions was 100 %.