Current Issue : April-June Volume : 2024 Issue Number : 2 Articles : 5 Articles
A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and strengthening mechanism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques are employed to examine the changes in the microstructure resulting from various solid solution treatments and aging treatments. The best strengthening effect can be achieved when the solubility of the MgSi phase and precipitate β (Mg2Si phase) is at their maximum. The addition of Er and Zr elements promotes the precipitation of the β phase and makes the b phase more finely dispersed. The aging strengthening of alloys is a comprehensive effect of the dislocation cutting mechanism and bypass mechanism, the joint effect of diffusion strengthening of Al3(Er,Zr) particles and the addition of Er and Zr elements promoting the precipitation strengthening of β phases. In this paper, by adding Er and Zr elements and exploring the optimal heat treatment system, the yield strength of the alloy reaches 437 MPa and the tensile strength reaches 453 MPa after solid solution treatment at 565 ◦C/30 min and aging at 175 ◦C/10 h....
In this investigation, the influence of using the EFWP filter on the tractor exhaust emissions was determined. A Water and paper filter is a filter designed to operate as a filter for the exhaust for the reduction of the harmful gas (CO, CO2, NOx, and HC) emission from the engine of the tractor. Emissions experiments were carried out on CASE JX75T tractor at different engine speeds are 750, 1000, 1250, 1500, 1750, 2000, and 2250 rpm. All engine speed of the tractor underwent experimentation before the installation of the EFWP filter and after installation it. The noises and Bsfec also were measured when the two cases. Each engine speed was tested for approximately 20 minutes in two cases. The results showed a significant (P≤0.05) decreasing in carbon monoxide CO (51.40%), carbon dioxide CO2 (25%), nitrogen oxides NOx (43.43%) and hydrocarbons HC (60.98%) emissions and also, the noises reduced by 25.38% and there was no significant increase in the BSFC (5.34% only) after the EFWP filter was put in the tractor exhaust. The results also showed that increasing the engine speed from 750 to 2250 rpm led to significant increases in CO2, NOx, and HC emissions, while decreased the CO emission. Also, the increased by a percentage of 155.88 and 159.38 % in the case using the EFWP filter and without using it (the ordinary case) respectively. Using the EFWP filter reduced the noises not overridden internationally permitted standards (65 dB)....
Structural components made of steel are used in several areas and require welding for assembly. In some situations, repair of the weld bead, also performed by electric arc welding, can be used to correct, and eliminate any discontinuities. However, electric arc welding causes the presence of residual stresses in the joint, which can impair its performance and not meet specific design requirements. In this paper, welded joints made of ASTM A 516 GR 70 steel plates, with a thickness of 30.5 mm, welded by the MAG—Metal Active Gas process (20% CO2) and using a “K” groove were analysed. The joints were manufactured with seven welding passes on each side of the groove. After welding, one batch underwent repair of the bead by TIG welding (Tungsten Insert Gas) and another batch underwent two repairs by TIG welding. Were presented results of the behaviour of the residual stress profile measured by X-ray diffraction and the Vickers microhardness profile in the joints as well the fracture toughness in the conditions only welded and submitted to repairs. The results indicated that the greater number of repair passes reduced the residual compressive stress values obtained in the material manufacturing process and caused a stabilization on the Vickers hardness values. It was concluded that compressive residual stresses did not play a major role in the R-curve results. The presence of discontinuities in the welded joint caused greater influence on the behaviour of the R curve....
To improve the heat transfer coefficient of a condenser, this paper proposes using a fintube condenser to replace a smooth-tube condenser in a domestic heat pump water heater. The finite element method is used to analyze the heat transfer coefficient of fin-tube condensers with different design parameters. By comparing the results of experiments with those obtained using CFD methods, it has been determined that the CFD method used in this study is feasible. Simulation results showed that the heat transfer coefficient enhanced clearly. The total thermal resistance of the fin-tube condenser decreased by 7% through increasing fin thickness. The total thermal resistance of the fin-tube condenser increased by 1–1.3% when fin spacing was increased. The heat transfer coefficient decreased severely and the maximum total thermal resistance of the fin-tube condenser increased by 8.7% with increasing fin height. In 600 s, when the fin spacing, fin height, fin thickness and inner diameter were 14 mm, 12.5 mm, 1.2 mm and 22.5 mm, respectively, compared to the smooth-tube condenser, the fin-tube condenser could increase the final water temperature by 18.37%, and the heat transfer coefficient would increase by about 95%. This research could provide a low-cost way to improve the heat transfer coefficient of condensers in domestic heat pump water heaters....
Coating a sword with a layer of clay prior to water quenching is one way to promote hardening and improve corrosion resistance. In this study, two types of clay coating were prepared on two identical steel swords (L04 and L05) in order to explore the effects of the addition of clay on the microstructure of steel. Samples taken from each blade were compared using metallography, XRD tests, microhardness tests, and electrochemical tests, and the results showed that L04 had a wavy pattern and contained pearlite, martensite, and residual austenite, while L05 had a mesh pattern and consisted of acicular and lath martensite. More importantly, the electrochemical tests indicated that L05 exhibited better corrosion resistance than L04. Each test zone of L05 (with icorr values of 2.48~8.08 μA·cm−2) had lower corrosion rates compared to the corresponding zones of L04 (with icorr values of 2.93~10.44 μA·cm−2). Furthermore, the calculated Rp values of each test zone of L05 (2341~8260 Ω·cm2) were higher than the values of the corresponding zone of L04 (1908~6716 Ω·cm2). These results further demonstrate that the second method of clay coating endowed superior anticorrosion performance. In addition, the overall strength and toughness of L04 were achieved with a lower hardness back (mean value 320 HV) and a higher hardness edge (mean value 850 HV), whereas the overall strength and toughness of L05 were achieved with a high hardness throughout (mean value 640 HV of the back and 725 HV of the edge)....
Loading....