نشریه مهندسی متالورژی و مواد
سال سی و سوم شماره 4 (زمستان 1401)

Cobalt ferrite is a magnetic material with a spinel structure. nano particles of Cobalt ferrite is attractive because of medium supersaturation, magnetic anisotropy,optical properties which causes to wide range applications such as drag delivery, cancer diagnosis and treatment, magneto-sensor, optical fibers and magneto-optical devices. In this investigation, the effect of reaction temperature on structure and magnetic properties of co-precipitated cobalt ferrite nanoparticles was studied. The nanoparticles were synthesized at 80, 90,100 and 110 C. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and vibration sample magnetometer (VSM) were used to charactization of nano particls. The results showed that cobalt ferrite nanoparticles was synthesized at all the reaction temperatures and supersaturation of non-calcination samples was noticeable. According to the results, by increasing the reaction temperature, crystallite size increased from 32 nm to 90 nm and also the magnetic supersaturation increased from 32 from 71.5 emu/g. besides, The purity of cobalt ferrite increased with increasing reaction temperature.

In this study, microstructure and wear behavior of Al-8Zn-3Mg-2.5Cu aluminum alloy matrix nanocomposite reinforced with 0.1, 0.3, 0.5, 0.7 and 1 wt.% graphene nano plates (GNPs) produced by stir casting and ultrasonic treatment have been investigated. Ultrasound device equipped with a cooling system with high powers was used for mixing alloy and nanoparticles. Also the microstructure and wear surfaces of nanocomposite was investigated by scanning electron microscope equipped with EDS analysis. The microstructural studies of the nanocomposite revealed that GNPs addition reduces the grain size, but adding high GNPs content (1 wt.%) does not change the grain size considerably. Further investigations on wear revealed that the addition of GNPs increases wear resistance . At high GNPs contents (1 wt.%), the presence of GNPs agglomerate on grain boundaries was found that causes decrease the wear resistance. The optimum amount of nanoparticles is 0.5 wt.% GNPs that nanocomposite exhibits bes wear resistance.

In this paper, the microstructure and compressive strength of A380 aluminum alloy were investigated by adding SiC nanoparticles. A380 aluminum powder and SiC nanoparticles with values (0, 0.5, 1, and 2% by weight) were ground in a planetary ball mill in an argon atmosphere for 10 hours. The ball weight ratio to powder was 10:1, and the rotation speed was set at 250 rpm. After the milling process, a hot press produced the samples. The products were produced through a graphite mold with a 15 mm diameter at a 10 °C heating rate per minute to a final 510 °C sintering temperature with a 30 minutes holding time under vacuum conditions. In addition, a pressure of 50 MPa was placed in the hot press machine. The microstructure and formed phases of the product samples were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Moreover, a universal testing machine (UTM) was used to test the compressive strength. It was observed that agglomeration occurred with the increase of SiC nanoparticles, which decreased the mechanical properties. The samples' best density and compressive strength were related to aluminum alloy with 0.5% by weight of SiC nanoparticle. Furthermore, due to the low sintering temperature, SiC decomposition did not occur. Besides, the intermetallic compound of aluminum with carbon or aluminum with silicon was not formed.

One of the most important problems of using magnesium alloys is their high corrosion rate. In order to solve this problem, the method of surface modification and coating has been considered. The main purpose of this research is to apply polycaprolactone/chitosan-1% Baghdadite polymer membrane by immersion method on anodized magnesium-aluminum AZ91 alloy in order to improve the corrosion resistance, biodegradability and biocompatibility of this alloy. The results of the electrochemical test show the improvement of the electrochemical resistance and the reduction of the electrochemical current density (10^3 times reduction) of the anodized magnesium-aluminum alloy AZ91 due to the application of the polymer-ceramic membrane. Also, the application of polymer-ceramic membrane has led to an increase in the surface roughness from 0.329 ± 0.02 (magnesium-aluminum AZ91) to 7.792 ± 0.34 micrometers. In order to evaluate the ability of apatite formation on the samples, the body simulating liquid test (phosphate buffer) was used. The results show that the formation of apatite layer on the surface of the sample can be considered as a measure of biodegradability

Brazing of low-carbon austenitic stainless steel sheets is applied to produce plate heat exchangers. In this study, the copper filler was used to join multiple layers of 316L steel plates due to its low cost, low melting temperature and relatively good bonding strength compared to other filler metals. For comparison, 2-layer and 5-layer specimens were brazed with the copper interlayer. fabricated. The sandwich joints have been fabricated under different process conditions of the brazing temperature (1070 and 1120°C) and the brazing time (30, 60, and 90 min). Detailed microstructural studies and hardness were carried out on the brazed joints. The microscopic studies showed that the joint formed at 1070 °C was not uniform compared to 1120 °C and the specimen brazed at 1120°C/90 min presented better properties due to enough time for melting of the interlayer and diffusion of elements. Also, 2-layer specimens with lower average grain size had higher hardness than 5-layer specimens.

In this article, the sensitivity analysis of heat treatment parameters including the solutioning time, ageing temperature, and addition of nano-particles on the hardness of the piston aluminum-silicon alloy (AlSi12CuNiMg) were characterized using regression analysis method. For such an objective, the clay nano-particles with 1 wt. % were used to fabricate the metal-matrix nano-composites and the standard specimens were produced using the gravity and stir-casting methods. To find the superior heat treatment conditions for aiming the maximum hardness, the solution treatment was performed at 500 ℃ for 1, 3, and 5 hours and the ageing treatment was done at 200, 215, and 230 ℃ for 6 hours on the base alloy and the metal-matrix nano-composites. Experimental results showed that the ageing treatment had the most effect on the material hardness and the solutioning time and nano-particles addition were the less effective parameters on the alloy hardness. The optimum heat treatment conditions achieved by the solutioning time of 5 hours and the ageing temperature of 200 ℃, during heat-treating which led to have the maximum hardness.