Key Engineering Materials Vol. 921

Abstract: Homogenization treatment is vital for eliminating eutectic structure and ensuring a preferable microstructure foundation for Aluminum Lithium (Al-Li) alloys. In this paper, solidification phases in an as-cast Al-Li alloy were revealed and their evolutions during multiple homogenization processes were analyzed by means of scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and differential scanning calorimetry (DSC) analysis. The results showed that the as-cast microstructure mainly contained needlelike Al₂CuLi and Al₂Cu phase, large size Cu-rich phases and netlike Ag-containing phases attached to them. As the alloy homogenized by 455°C/16h, except for needle-like phases inside grains, part of phases on grain boundaries had dissolved into the matrix and exhibited rounded shapes. As homogenized by 455°C/16h+495°C/16h, Ag-containing phase had completely dissolved into the matrix while the Cu-rich phases remained and showed two different morphologies depending on whether Mg element was contained. Prolonging the second homogenization time to 28h, no obvious change occurred for the Cu-rich phase. As homogenized by 455°C/16h+495°C/20h+512°C/20h, most Cu-rich phase had dissolved into the matrix while residual phase was mainly Fe-containing phase. This proposes an effective way to eliminate various solidification phases in Al-Li alloys and identify their contents.

Abstract: Grain characteristics are one of the most important factors in determining alloy properties. Thermal deformation and solution treatment experiments were used to investigate the evolution of grain features and mechanical properties of Al-9.39 Zn-1.92 Mg-1.98 Cu alloy. The results reveal that when the deformation temperature rises, the recrystallized grain size, recrystallization fraction, and sub-grain size for the alloy's final microstructure gradually increase. The recrystallized grain size and fraction increase as the solution temperature rises, although the sub-grain size of the final microstructure of the corresponding alloy changes slightly. Fitting is used to deriving the function of recrystallization size, recrystallization fraction, and sub-grain size as a function of deformation temperature. The tensile properties of the alloy at T6 state are the best after deformation at 400°C and solution treatment at 470°C. The brittle fracture mode is shown in recrystallized grains, whereas the toughness fracture mode is shown in sub-grains.

Abstract: Pre-deformation is usually indispensable to obtain an appropriate balance between microstructure and mechanical properties of Al-Cu-Li alloys. In this paper, the effect of pre-deformation degree on the evolution of strength, fracture toughness, and precipitates during artificial aging processes of a novel Al-Cu-Li alloy was studied. The results indicated that the amount of T₁ phase increased remarkably while the precipitation of θ' phase was inhibited with the increase of pre-deformation degree. The change in the average size of T₁ phase indicated that the increase in nucleation sites suppressed the full growth of T₁ phases. The fracture toughness could be related to the strength difference between intragranular and intergranular. Based on the matching of properties, a reasonable pre-deformation parameter was proposed.

Abstract: To control the product density uniformity and weight reduction for metal injection molding (MIM), this study investigated the influence of using gas-assisted technology to assess if uniform part density can be achieved. The findings show that gas-assisted molding has great potential for improving density uniformity, particularly for the part density at the position far away from the gate. The green parts and final parts also significantly improve density uniformity and shrinkage. Interestingly, the gas-assisted technology applied to MIM shows similar molding characteristics and advantages over gas-assisted injection molding of polymers. This also enables the design of MIM parts with a non-uniform thickness with a hollowed core in the thick portion.

Abstract: The finite element software abaqus is used to establish the model of split-sleeve cold extrusion (elastic-plastic) of the 7050 aluminum alloy test plate with hole and the reaming model after cold extrusion, and the processes are simulated. In these processes, the simulation results of cold extrusion are compared with the measured results, the law of residual stress distribution after cold extrusion is explored, and the influence of the amount of reaming on the distribution of residual stress during the reaming process is discussed. The simulation results show a good agreement with the experimental data; the residual compressive stress after cold extrusion increases first and then decreases from the intrusion end to the extrusion end. Specifically, the maximum value is near the middle surface, and the value of the second half is larger than that of the first half; after the cold extrusion with the split sleeve, a "ridge" appears, leading to uneven distribution of the residual stress and extrusion amount along the circumference of the hole. Moreover, the minimum value of the tangential residual stress lies on the intrusion surface, vertical to the “ridge”. After reaming, new residual compressive stress will be introduced, which will increase the residual compressive stress on the intrusion surface. In this sense, proper reaming can increase the residual compressive stress and its peak value, resulting in a fatigue gain.

Abstract: Terbium metal rod with the dimension of 6.8mm in diameter and 150mm in length has been purified by solid state electrotransport (SSE) at 1050°C under a pressure of 10^-5Pa for 50h, and the impurity distribution has been determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The research results indicate that, the rare earth impurity migrates from cathode to anode of the rod, and the impurity distribution is relatively uniform in the longitudinal section; low melting point impurity of Al migrates from cathode to anode and the impurity concentration distribution is relatively uniform in the longitudinal section, the segregation degree is about 10% in each sample; the impurity with high melting point, Ta, W, Mo, etc., the distribution of above impurity is very non-uniform, for the impurity of Ta, the mean concentration of sample 7 is only 8.75 ppm, but the local concentration is up to 350 ppm, and it exists in an elementary substance form in the Tb; non-rare earth impurity in Tb metal, such as Ni, Si and Ti, migrates from cathode to anode of the rod significantly; the total impurity content in cathode end is lower than other posion, the impurty content of 22 imputies in sample 6 is 648.47 ppm, is the lowest in the Tb rod, except for the high melting point impurities, the lowest impurity content is 60.05ppm in sample 7.

Abstract: The variation in the modes of a new ruthenium diphenyl carbazide complex (RuDPC) during changing of ruthenium (Ru) concentration within 0.01 ≤ X ≤ 0.09 in diphenyl carbazide (DPC) are investigated using IR analysis. Variation in some IR spectroscopic parameters during the increase of Ru content in pure DPC has been recorded. The variation in both the relaxation time and the rotational energy barrier for RuDPC samples at the mode 505 cm^-1 supports a change that occurs at X ≈ 0.05. Micro-structure of RuDPC samples was studied by X-ray analysis and scanning electron microscopy. Moreover, SEM pictures and EDAX measurements were made revealing the strong Ru-signals indicating the presence of Ru and their distributions in the DPC matrix. Also results indicated that Ru inclusion in DPC matrix changes its morphology with a uniform distribution of Ru. Besides, X-ray diffraction patterns revealed RuDPC samples are represented by a mixture of amorphous and crystalline structure, wherever the phase-nature crystallization of RuDPC samples reinforced when the concentration of Ru is augmented. The crystal structure is changed to tetragonal structure after addition of ruthenium metal to pure orthorhombic DPC matrix. The spectroscopic properties of RuDPC complex is seemed to be dependent on its characteristics to the effect of radiation (FTIR), as a solar material in the application of this field; due to DPC is a photosensitive material, so that there are a number of optical applications which depend upon optically induced structure transition energy states for the complex.

Abstract: Wastewater treatment by nanotechnology, specifically magnetic nanosorbent as nanoZero Valent Iron (nZVI), is a new technology for degradation of wide ranges of organic pollutants by the effect of free electrons as Advanced Oxidation Processes (AOPs) and adsorption processes. Due to their effectiveness, economic, and safety properties, this study prepared and characterized nZVI to be entrapped into natural alginate biopolymer (Ag/nZVI). The removal of wastewater chemical pollutants was tested by studying the variations of COD levels. The effect of operating conditions was studied at different pH, Ag/nZVI doses (g/L), contact time (min), stirring rate (rpm), and initial COD concentrations. Also, Adsorption isotherm, kinetic studies were conducted to estimate equilibrated reaction mechanisms. Linear regression analysis was tested to find the Response Surface Methodology (RSM) relations between variables and removal percentages. Nonlinear Feed-Forward backpropagation system was built for Artificial intelligence neural networks (ANNs) importance detections. Finally, this study approved effective COD removal percentages reached 76%. The maximum removal efficiency for initial COD concentration 400 mg/L was observed at pH 6, using wet dose 3g/L, 30min, and 150 rpm.

Abstract: The utilization of Sewage Sludge Ash Pellets (SSAP) as an efficient sorbent material for dye removal is highlighted in this work. On MB removal, the effects of several factors such as contact time, agitation speed, solution pH, adsorbent dosage, and beginning concentration were investigated. When the MB concentration was 25 mg/L, the SSAP concentration was 30 g/L, and the speed was 250 rpm, the maximum removal efficiency was 98 %. The equilibrium time was found to be 60 minutes, and the maximum dye removal occurred at pH 10 for SSAP adsorbents. The Langmuir and Freundlich isotherm models were used to analyze the adsorption data. Adsorption isotherm studies revealed that the Langmuir model fits this case better. In most cases, the R² correlation coefficient value exceeds 0.95. According to the findings of this study, SSAP can be used as an effective adsorbent for the removal of MB from aqueous solutions.

Abstract: Nanotechnology especially Zero Valent metals is a modern technology for the degradation of extensive ranges of biological wastewater contaminants. Due to their effectiveness, economically and safely properties, this study successfully prepared and characterized nanoZero Valent Iron (nZVI) to be encapsulated into natural alginate biopolymer. The effect of operating parameters was studied at different environmental conditions; pH, dose (g/L), contact time (min), stirring rate (rpm), and BOD concentrations. Adsorption isotherm, kinetic studies, and statistical analysis (Response Surface Methodology (RSM) and Artificial neural networks (ANNs)) were examined to describe the removal behavior. The obtained results indicated that the maximum removal efficiency was 81.2 % for initial BOD concentration 300 mg/L, at pH 7, using wet dose 3g/L, 25min, and stirring rate 200 rpm. Also, adsorption and kinetic data indicated that the adsorption mechanism runs toward the Sips model to approximate the Freundlich model at low concentration and to solve the Freundlich limitation at high concentration with a maximum adsorption capacity of 181mg/g. Kinetic results describe the solid transformation from one phase to another at a constant temperature by approving Avrami model. Finally, RSM results agree with ANNs results that the “Concentration effect” is the most significant variable that controls the removal efficiency.