نشریه مهندسی متالورژی و مواد
سال سی و سوم شماره 2 (بهار و تابستان 1401)

The aim of this study is to investigate the fatigue behavior of GFRP composite with biaxial fiber orientation [0,90] under different stress levels. First, the tensile test was performed and the UTS value was 420 MPa. Then, fatigue test was performed at 4 stress levels of 70, 50, 42 and 35% of UTS. Fatigue results had acceptable dispersion and the fitting curve on the data also matched well. Finally, the fatigue failure structures of 70 and 35% of UTS samples, using scanning electron microscopy (SEM) were evaluated. The results showed that in both 70 and 35% samples, the mechanism of pull out fibers was obsvered but its intensity was higher in 35% sample. Also in the 35% sample, significant distortion was observed which was absent in the 70% sample. On the other hand, the brittle failure of matrix was more pronounced in the 70% sample than in the 35% sample. This can be related to the increase of the matrix softness due to the application of cyclic load.

Amorphous slag from the electric arc furnace of Mobarakeh Steel Company, and soda ash flute glass waste (window, mixed with equal weight ratio and sintered with foaming agents and used to prepare glass-ceramic foam. Five types of foaming agents including silicon carbide, calcium carbonate, chromium oxide, graphite and barium carbonate were added to the base composition in five amounts and sintered at 1200 ° C.The crystalline phase crystallized in the composite was at a low weight percentage of foaming agent wollastonite and with increasing weight percentage by 5% Pesudo wollastonite-.The highest volume increase is related to the sample with 5% by weight of barium carbonate and the highest porosity is related to silicon carbide with 1% by weight.The highest compressive strength among the three approved compounds reaches 4.8 MPa in terms of microstructural content of the sample with a weight percentage of calcium carbonate.Also, the distribution of porosity in all foam foams used is non-uniform and only chromium oxide has a better distribution than others.

In this paper, the effects of the aging temperature on the microstructure, mechanical properties, and electrical conductivity of Cu-0.4% Cr are investigated. The solid solution treatment was performed at 950 ᵒC for 1 hour. Then the samples were aged 5 hours at 200, 300, 400, 500, and 600 ᵒC. The microstructure of the samples was surveyed using FESEM. An analytical model is also developed to predict the age-hardened samples yield stress and the precipitation of the alloying elements based on the microstructure images analysis and electrical conductivity of the samples. Increasing the aging temperature up to 500 ᵒC, the number of precipitates increases and their size decreases. Yield strength, tensile strength, and work hardening exponent at aging temperatures of 200 and 300 ᵒC decreases a little and increases at 400 and 500 ᵒC and then decreases at higher temperatures. In optimum precipitation hardening conditions, the yield strength and tensile strength are higher 51.7 and 21.7% than solid solution treatment, respectively. Electrical conductivity increases by the aging temperature increasing up to 500 ᵒC and then remains almost constant at higher temperatures. Comparison between the tensile test and the present model results shows that the model is capable to predict the yield strength of the age hardened samples by good accuracy.

This study investigated the effect of adding boron carbide microparticles (B4C) and titanium diboride nanoparticles (TiB2) on the microstructure, tensile strength, and hardness of A356 aluminum composite. In so doing, 2.5, 5, and 7.5 vol.% B4C reinforcements and 2.5 vol.% TiB2 reinforcement were added to the field by stir casting at 1000 °C using in situ process. The TiB2 nanoparticles were processed in situ by cryolite precursors (Na3AlF6), titanium oxide (TiO2), and potassium tetrafluoroborate (KBF4) in aluminum melt, and B4C microparticles were added directly into the melt. X-ray diffraction (XRD), optical microscope (OM), and scanning electron microscope (SEM) were used to investigate the microstructure and failure mechanism of the samples. Also, hardness and tensile tests were carried out to test mechanical properties. The results showed that addition of B4C first decreased and then increased the ultimate tensile strength compared to the sample without reinforcement. Moreover, the highest value of tensile strength was for the sample containing 2.5 vol.% of B4C and 2.5 vol.% TiB2, which showed a 235% improvement compared to the sample without an amplifier. However, the tensile strength of the sample containing 2.5 vol.% of B4C was reduced by 35% compared to the sample without reinforcement. The results of the hardness test showed a drop in properties of the samples containing 2.5% of B4C reinforcement. the highest value of tensile strength was for the sample containing 2.5 vol.% of B4C and 2.5 vol.% TiB2, which showed a 33% improvement compared to the sample without reinforcement.

One of the practical methods for developing high strength steels with suitable ductility is quenching and partitioning process to create a micro-composite microstructure (martensite + residual austenite). In this regard, a good combination of mechanical properties can be produced in a low-alloy steel with a low cost. In the present study, a medium silicon carbon steel 1.7102 was studied by applying quenching and partitioning processes. For this purpose, the effect of quenching temperature (temperature range 170 to 230 °C) and partitioning time (3 to 30 min) were investigated on the microstructure and tensile properties. Microstructural observation was carried out by light microscopy and the volume fraction of the retained austenite was determined using the X-ray diffraction technique. The results show that quenched and partitioned microstructure contains micro-composite features. Moreover, the amount of retained austenite was reduced by increasing the partitioning time followed by precipitation of carbide phase. The best tensile properties were obtained for the specimen quenched at 170 ° C and partitioned at 300 ° C for 8 minutes with a tensile strength of 1997 MPa, yield strength of 1730 MPa, elongation of 10.3% and reduction area of 48%.

In this experimental work, the improvement of microstructure and mechanical behavior of medium silicon low alloy 35CHGSA steel have been investigated under quenching and partitioning heat treatment in comparison to conventional direct water quenching and tempering condition. For this purpose, the samples of medium silicon low alloy 35CHGSA steel were first austenitized at 900˚C for 15 min and then cooled to room temperature. By the following two heat treatment methods. In the first method, the austenitized, samples were directly quenched in water and then tempered at 500°C for 60 min (Q&T). In the second method, the austenitized samples were quenched in the molten salt bath at 230°C for 1 min in order to form some martensite and then heated to 400°C for 12 min for carbon partitioning from martensite to the adjacent remaining austenite areas and finally water quenching (Q&P). Hardness and tensile tests were performed with phase analysis by XRD and microstructural observations under optical microscopy, field emission scanning electron microscopy (FESEM) equipped with energy-dispersive spectrometry (EDS), followed with electron diffraction via transmission electron microscope (TEM). The results show that the Q&P heat treatment process has been associated with the significant improvement in microstructure and mechanical properties of medium silicon low alloy steel compared to conventional water quenching and tempering condition. The product of ultimate tensile strength multiple elongation, which is a good criterion for design and development of advanced high strength steels, is significantly increased from 16.4 (Q&T samples) to 25.5% GPa (Q&P samples).

In recent years, manganese oxides (MnO2, Mn2O3, Mn3O4, MnO) have drawn the attention of many researchers due to their physicochemical properties and potential applications. Manganese dioxide, among manganese oxides, exists in several different polymorphs including α, β, γ, δ, λ-MnO2, which crystal structure determines many of its functional properties, including magnetic properties, electrochemical identification, molecular absorption, and properties. To date, various methods have been employed to synthesize these materials. This study proposes a method of solution combustion synthesis to synthesize manganese oxides in a single step. This study seeks to determine whether changes in fuel type, φ value, adiabatic temperature, and number of additives affect the stability of manganese oxide structure. The synthesized particles were then analyzed using X-ray diffraction and FE-SEM microstructural analysis. Studies have demonstrated that φ ˂ 1 and urea are the optimal conditions for the synthesis. Likewise, in order to determine the effects of heat treatment on the crystallinity of the synthesized particles in different conditions, heat treatment was carried out, which increased crystallinity in the samples. Despite the difficulty of synthesizing manganese oxides, particularly MnO2, the present study was able to perform it in a single step via solution combustion synthesis.

In this study, the solution combustion method was used to synthesize a bioactive borate compound. XRD, FTIR, PSA analyses have been used to identify phase composition, bond determination, and particle size, respectively. In addition, MTT and cell migration 3assay were utilized to measure the biocompatibility of the particles. The synthesized particles not only were nano in size along with amorphous structure, but also showed positive effects on cell proliferation and migration. To attain bioactive compositional scaffolds, the borate amorphous compound was combined with hydroxyapatite nanoparticles at different weight percentages. Afterward, mixtures were sintered at 600, 650, and 700 oC for 0.5 and 1 h. XRD and DTS analyses were operated to evaluate the phase composition and mechanical strength. FESEM micrograph was evaluated to observe the crack path in addition to porosity andthe effect of borate glass on the sintering process. The sample sintered at 700 oC for 1h containing 20% borate glass and 80% of hydroxyapatite, accounted for the highest mechanical strength at 4.87 ± 0.02 MPa. ICP-OES analysis of the sample containing 20% hydroxyapatite, which was sintered at 700 oC for 1 h, showed an increase in ion release compared to pure sintered hydroxyapatite after immersing in SBF for 7 days. Also, ion release of the borate glass has considerably been controlled and diminished by virtue of combining and sintering with hydroxyapatite nanoparticles. Furthermore, the mentioned composition is able to bond with soft tissue as well as hard tissue.

With the emergence of industries and their growth, joining different parts to each other has become an important need. Due to the complexity of conventional connection methods, there has been a great deal of interest in research and development of new connection methods in recent years. Therefore, this study was conducted to investigate the joining strength of 5083 aluminum alloy to a polymer-based composite reinforced with carbon black particles. In this study, mechanical properties including shear tensile strength and the effect of reinforcing particles on the thermal conductivity of high density polyethylene were investigated. In this study, the joining was performed by friction stir welding process and the weld point strength was investigated by shear tensile test. Percentage of reinforcing phase added to the polyethylene matrix, dwell time of friction stir spot welding machine tools as variables affecting the shear tensile strength were evaluated in this study. The results showed that by increasing the dwell time for pure polyethylene for 15 seconds and for composite samples of carbon black reinforced polyethylene in a time period of 10 seconds, a favorable bond was established and with increasing dwell time Up to 20 seconds due to excessive increase of polyethylene melt strength and residual stresses during the freezing process, a decreasing trend of bond strength was observed.

In this work, the effect of laser line interruption was studied on the structure and magnetic properties of grain-oriented silicon steel sheets during the laser-scribing process in the presence/absence of an external magnetic field. By applying different patterns of interruption, the effect of discontinuity length, one-sided or two-sided application of laser and overlapping or non-overlapping of laser lines (for sheets scribed on both sides) was investigated on the domain structure and core losses of silicon steel sheets. Based on the results of these experiments, the optimal conditions of discontinuous laser scribing were obtained. The results show that although at small interruption lengths such as 2 mm, the effect of laser scribing is negligible on reducing the core losses, but by increasing the interruption length to about 6 mm, the magnetic losses are greatly improved. By re-increasing the length of interruption to about 10 mm, the core losses increase again and this indicates that a break length of 6 mm creates optimal core losses in the sheets. Use of a longitudinal external magnetic field during the discontinuous laser irradiation with an optimum interruption pattern results in a reduction of about 16% in core losses in grain-oriented silicon steel sheets.

Through the reaction of iron and silicon powder system, different types of iron silicides can form. Depending on their structure, the iron silicide exhibit metallic, semiconductor, or insulating behavior. The higher the iron contents of these materials, the stronger their magnetic properties. One of the technical problems in using elemental powder to produce the different types of silicides is predicting the final component of iron silicide. So far, no comprehensive research has been conducted on this goal. Therefore, in this study, based on the thermodynamic data and with the help of HSC software, the iron silicon phases will form in each molar ratio of iron and silicon were predicted. Then, three different molar ratios were examined in the laboratory for practical evaluation of this prediction. The results showed that by increasing the molar ratio of silicon from 0.5 to 1 and 2, respectively, the Fe3Si, FeSi, and FeSi2 phases will be the predominant phases, which almost agreed with the actual thermodynamic predictions. The reasons for the differences were also discussed.

In this study, the effect of copper addition on the microstructure of the 410s stainless steel was investigated by means of scanning electron microscopy which was equipped with energy dispersive X-ray spectroscopy (EDS). Also the phase equilibria and the phase fractions at 1000℃ were calculated using the software package MatCalc version 6.00. The samples were solution annealed at 1000℃ and quenched in oil. According to the results of thermodynamic calculations and scanning electron microscopy images, dual-phase steel with microstructure including ferrite and martensite was formed. It was found that by increasing the amount of copper in the chemical composition of steel, the weight fraction of the ferrite phase in the microstructure decreases remarkably. The phase fraction of ferrite decreases with increasing copper content in agreement with the thermodynamic calculations. The addition of about 5 wt.% copper eliminated the ferrite phase and led to a fully martensite microstructure in the quenched samples.