a. anbarzadeh

Precipitation Hardenable Aluminum Alloys are suitable alternatives in electric vehicle bodies due to their lower specific weight compared to steel. Therefore, the development and understanding of the properties of aluminum alloys help to develop electric vehicles, reduce greenhouse gas emissions, and control global warming. In this research, we investigated the heat treatment of AA2024-T4 and AA6061-T6 alloys at a temperature of 453 °C for 210 minutes in a tube furnace with a heating rate of 5 oC/min in a vacuum (7.5×10-13 Torr). The alloys were assessed by optical microscopy (OM), scanning electron microscopy (SEM), and hardness test. The effect of heat treatment was investigated on the particle size as well as the phases. The particle diameter and hardness value of AA2024-T4 decreased after heat treatment. The number of precipitates in AA2024-T4 increased after heat treatment. Precipitates size in AA6061-T6 alloy remained almost unchanged after the heat treatment.

The main minerals containing chromium are chromite mineral compounds. Ferrochrome is divided into three groups: high carbon, medium carbon and low carbon. Chromite mineral has a cubic lattice and belongs to spinel category. In the present study, Fe-Cr-C three-component diagrams are presented along with chemical compounds of ferrochromium. In the following, the extraction of high carbon ferrochromium is further investigated. Fe-Cr-C ternary diagrams confirm that Cr3C2 decomposition at temperatures below 1600°C in minerals with 60 wt% Cr and 8 wt% C results in Cr7C3 composition. Finally, a solution to reduce the most toxic chromium ion (Cr6+) in the leachate of the extraction process is presented. Cr6+ is the most toxic species among its different oxidation states. Cr6+ is also toxic to aquatic animals, plants, and bacteria. Cr3+ is 100 times less toxic than Cr6+. In humans and in small quantities, chromium is an essential nutrient required for sugar and lipid metabolism, but in excess it may cause cancer and allergic skin reactions.

In this study, to bond AA2024 and AA6061 alloys to each other, three elements (Sn, Zn and Ga)  were considered as interlayer elements in terms of atomic diffusion depth in the base metal and storage at 453°C for 2 days, 10 hours, 210 minutes, and 30 seconds that they were examined for atomic diffusion modeling. Finally, the two alloys were connected at a temperature of 453°C in a furnace environment under a vacuum of 7.5×10-13 Torr under a transient liquid phase process. The effect of changing the thickness of the interlayer on the connection of the two alloys are examined with practical tests such as metallography, SEM, the distribution map of the elements, hardness test, the linear scan of the elements at the joint, and tensile strength test in two modes, 1: investigating the effect of changing the thickness of the interlayer on strength, and 2: investigating the change in joint strength by increasing sample retention time in the furnace. As the thickness of the interlayer increases (from 20 to 70 μm), the bond strength decreases. The maximum tensile strength of joint with the 20 μm thickness Sn-5.3Ag-4.6Bi interlayer is 52 MPa.

In this research, dissimilar laser spot welding of the Ti-6Al-4V and AISI 304 (stainless steel) was investigated. The joining of 0.7 and 0.5 mm thickness plates with using a copper interlayer of 0.2 and 0.3 mm in thickness was performed by LSW. A 400-W Nd: YAG laser pulse welding machine was used to obtain coaxial spot welds of 4 mm in diameter with circular technique. Visual inspection and metallographic examination were used for all samples. If no crack was identified, micro-Vickers hardness test, tensile test, and scanning electron microscopy (SEM) were performed on the samples. The result indicated that with a copper interlayer and 10.7 J heat input on peak power of 1.5 kW, welding frequency 15 Hz, and welding time of 7 ms, leading to an ultimate strength of 160 MPa.  In addition the result indicated that applying the circular technique by creating adjacent spot welds can produce a good joint.

Metal-based nanocomposite coating prepared by plating method can exhibit unique mechanical, chemical, and physical features which have led to their extensive application in various high-tech industries. Nickel-based nanocomposite coatings can pose far lower pollution toward the environment and related staff as compared with chromium-based ones. In this research, a novel compound was developed to coat nickel-alumina nanocomposite by adding formaldehyde to the plating bath. The concentration of alumina nanoparticles (NPs) in the plating bath was 10 g/L. The nickel-alumina nanocomposite coatings were prepared by a pulsed electrical current under ultrasound turbulence in the plating bath. Two Ni bathes in combination with Watt’s compound were used with and without formaldehyde addition. Before plating, the zeta potential of alumina NPs was measured in the two different baths. After plating, the cross-section of the coatings and the alumina content participated in the coating, as well as the coating morphology, were analyzed by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). Based on the results, incorporation of formaldehyde into the Watt’s solution increased the zeta potential of the nanoparticles from -4.1 to +30.5 mV; consequently, the nanoparticle content of the coatings enhanced from 4.6 to 8.5 vol.%.

Knowledge of the measurable parameters in an electric arc furnace can effectively increase efficiency while declining energy consumption, hence leading to positive environmental consequences. This issue has been frequently addressed in various studies, but the extent of these effects and their cause-effect relationships have been rarely explored. In decision-making procedures that depend on various factors, the extent of the effect could be also effective in addition to the priority. The optimization and the effect intensity, as well as affectability of some effective parameters of an electric arc furnace, can dramatically influence the quality of the produced steel, energy consumption of the process, and consumption of electrode and refractory substances. The aim of this study is thus to examine the mutual effects of various carbon injection contents, electrical power consumption levels, slag, and other effective parameters of the electric arc furnace during different charges including material and energy consumption, volume and quality of the slag, and pollutant emission using the DEMATEL mathematical model.  To this end, calculations of some of the recorded parameters of a 110-ton electrical arc furnace in the Khorasan steel complex were studied and compared.