Sharif Digital Repository

Severe plastic deformation (SPD) is an ideal approach to fabricate light-weight alloys, such as aluminum alloys, with ultrafine-grained (UFG) structure up to nano-scale. Thus, it is known as a process that boosts the strength of materials. This method is also adopted to enhance the specific strength of materials, which is essential in the transportation and aerospace industries. Because of limitations like load capacity, and as a result, low-size productions, it is not possible to use them in industries. A practical solution is to join the productions and fabricate them on bigger scales. Welding of SPDed materials by employing solid-state welding techniques is appropriate for joining UFG... 

Ultrasonic metal welding is a solid state welding process and is widely used in welding the connections of lithium-ion battery batteries in hybrid and plug-in hybrid vehicles. This welding process has advantages over fusion welding processes such as; Shorter time, no heat affected area, optimal energy consumption, cheaper equipment and no harm to the environment. The aim of this study was to investigate the effect and optimization of time, normal pressure and oscillation amplitude parameters in order to achieve the maximum tensile-shear test force and T-peel test in the dissimilar welding of 1050 aluminum and copper (purity above 99.9%). In order to achieve the optimal state of welding... 

In this study, the ST14 low carbon steel sheet was used as a skin layer in the construction of three-layer laminates. The use of this steel was due to its high mechanical properties and excellent formability. A thermoplastic polyurethane sheet was also used as the core layer. The selection criteria of this polymer were no need for adhesive (for bonding metal to polymer) as well as proper mechanical properties (elongation and strength) and physical (density). The perfect process for manufacturing three-layer laminates is the roll bonding process. To manufacturing a laminate with the desired properties of the designer, the rolling parameters (rolling speed and thickness reduction) must be... 

Demand for high performance components has caused a propensity towards high strength alloys, especially 7000 series, having extended applications in aerospace, automotive and medical industries. Due to high strength, heat treatability, and optimum weight, these alloys have been implemented in various conditions, specifically AA7075, being directly used in airframes. Through the years, numerous attempts have been made to improve the corrosion and formability properties of these alloys, resulting in the development of various tempering methods such as retrogression and re-ageing. Despite achiving optimal properties, it has been of less interest through literature to assess the formability of... 

In this study, the mechanical properties of composite sheet polymer matrix reinforced with steel mesh were investigated. This bonding was carried out by rolling of a three layers of steel mesh in between two composite polymer sheets. Then, the effective parameters of process; Sample maintenance temperature inside the furnace, reduction during rolling, rolling speed, rolling direction and Number of rolling passes were investigated to determine the optimized processing conditions. In this way, adding mesh to the polymeric matrix improves the strength and polymer / polymer bond in the sandwich structure. Placing the mesh in the sandwich structure converts the brittle behavior of the polymeric... 

The precipitation hardenable 7075 Aluminum Alloy is one of the most important heat-treated aluminum alloys. The high strength of this alloy has led to its widespread use in the manufacture of various components in the automotive, aerospace, marine, defense and military industries. Although the production costs of this alloy sheet are high, but since the 7075 aluminum alloy has the capacity to be as strong as steels, by reducing the production process and thus reducing production costs, this alloy can be used more widely in various industries. Therefore, in this study, the mechanical properties of the 7075 aluminum sheet are improved by a new quenching method in the die (HFDQ), which is a... 

Considering the wide applications of 304 stainless steel in various industries and the existing literature on transient liquid phase bonding of stainless steels with a variety of interlayers, the present work aimed to reduce the bonding time by using a two step bonding method. Faster bonding reduces both energy consumption during bonding and the base metal grain growth. It also leads to a lower reduction in the base metal and joint strength.Due to the melting point of the interlayer, different durations and a temperature of 1200°C were selected for the first step. This temperature was maintained for a specified period of time before it sharply dropped to and remained at 1180°C (the... 

In recent years, Jam Petrochemical has produced and designed irrigation tape polyethylene grades but because these grades don’t have sufficient melt strength during high-speed processing, it hasn’t been welcomed by manufacturers. Therefore, in first step of this study we tried to characterize the specimens by using referenced grade and by taking advantages of thermal, rheological and mechanical analysis. We observed that main difference between jam petrochemical grades and referenced grade is related to type and content of comonomer and also long chain branches. Based on the obtained results, the ideal molecular structure of irrigation tape grade, include chains with bimodal distribution... 

In this study, in situ Al-Al3Ti-Al2O3 nanocomposite has been fabricated on thermal decomposition of tialite (Al2TiO5 or AT) precursor in the aluminum matrix through powder metallurgy method. The high-temperature mechanical property of Al-Al3Ti-Al2O3 on this procedure has been investigated. In the first step nano-structured tialite were synthesized through citrate sol-gel methods. Then 3.5 wt.% tialite powder was mixed with aluminum by high energy vibratory milling for 3 hours. In the next step, green compacts of mechanically milled powder mixtures were sintered at 530°С for 6 hours under argon atmosphere. In the final step, hot extrusion as a consolidation method reduces the sample voids,... 

Quince seed gum is a natural material that was used in Iranian traditional medicine for wound treatment. Alginate is a beneficial biomaterial that has been used in making commercial wound dressings for a long time. In this work, the preparation method and properties of films based on Alginate and Quince seed gum for drug delivery and wound healing have been investigated. According to the obtained results about crosslinking and plasticizing, the suitable condition of synthesis is 0.5% CaCl2 concentration, 2min soaking time, and 13% glycerol in crosslinking solution. In this crosslinking solution, a film with good mechanical properties (tensile strength: 13MPa, elongation: 27.3%, and Young’s... 

Low carbon steel sheets have many applications in the automotive industry. The mechanical properties and ductility of the steel change significantly by the aging phenomena. In this study, the effects of temperature and time of quench aging phenomenon on the tensile properties and formability of a low carbon steel sheet has been investigated. Samples with dimensions of 10×10 cm were prepared for the Erichsen test and also samples with geometry in ASTM E8 standard were prepared for the tensile test of the steel sheet. After performing solution treatment on the samples at 650 °C, they were rapidly cooled to room temperature (25 °C) and then placed in water, air and oil at certain temperatures... 

Polymeric film for packaging applications are commonly made from a variety of polyethylenes using a blown film process. Nowadays high density polyethylene with bimodal molecular weight distributions are used to improve the performance and the final properties. In the present study samples with different bimodal molecular weight distribution in a similar film preparation are developed. The EX5 sample from the Jam Petrochemical showed microstructure with heavily oriented stack of lamellae in the machine direction. In contrast, the 7000F sample from the Mehr Petrochemical presented a microstructure with a lower degree of lamellae, containing lamella twist and more link between the crystalline... 

This study investigates effect of cold roll prior to inter-critical annealing on microstructure and mechanical properties of ferrite-martensite dual phase steel. Samples were heated to 850oC for 1h followed by oil quench, then the steel sheet were cold rolled by 0%,10%,15% and 20% reduction in thickness, Then an inter-critical annealing(750oC,120min) was performed to generate a ferrite-martensite microstructure. Microstructural study showed that increase in applied Cold roll, leading to increase volume fraction of martensite and decrease in ferrite grain size. Mechanical properties of dual phase steel were tested by Tensile test, impact test and micro-hardness Test. Results shows that... 

This study investigates effect of cold roll prior to inter-critical annealing on microstructure and mechanical properties of ferrite-martensite dual phase steel. Samples were heated to 850oC for 1h followed by oil quench, then the steel sheet were cold rolled by 0%,10%,15% and 20% reduction in thickness, Then an inter-critical annealing(750oC,120min) was performed to generate a ferrite-martensite microstructure. Microstructural study showed that increase in applied Cold roll, leading to increase volume fraction of martensite and decrease in ferrite grain size. Mechanical properties of dual phase steel were tested by Tensile test, impact test and micro-hardness Test. Results shows that... 

Many researches have been done on the severe plastic deformation of 2024 aluminum alloy, but there is limited information on the effect of severe plastic deformation for this alloy in the over-aged condition. In this study, the effect of severe plastic deformation and annealing heat treatment on the microstructure and strength of the over-aged AA2024 has been investigated. 1, 3, 5 and 7 two-dimensional multi-directional forging passes carried out to the over-aged samples at room temperature as one of the methods of severe plastic deformation process. After applying strain, samples were subjected to annealing heat treatment at 200, 300 and 400 °C for 30 minutes and then quenched in water. For... 

In this study, the effect of martensite volume fraction on the wear behaviour of 4340 steel with triple-phase steel microstructure with a constant volume fraction of 34% ferrite was investigated. Using the Holman equation, it was found that triple-phase steel with different martensite volume fraction has two stages of work hardening. By increasing martensite volume fraction, yield strength and ultimate tensile strength and work hardening exponent of first and second stages increase and the elongation decreased. To perform the wear test, the pin on disc apparatus was used according to the ASTM G99 standard, and the test was done at two forces of 10 and 50 N at a fixed distance of 400 m. The... 

In this research, we studied the effect of compatibilizer and short glass fiber on microstructure and mechanical properties of PBT/PC blends. Fisrt, Antioxidants and sodium pyrophosphate dibasic were used to suppress transesterification in PBT/PC Blend. The results showed that best composition occur when both of them are used. In the next step, we used 3%wt MBS (methyl methacrylate-butadiene-styrene) and saw that this weight percent of this compatibilizer doesn’t useful. Moreover addition of short glass fiber to PBT/PC was examined and the results showed that mechanical properties of composite are extensively increased. Also in this step, we proved this idea that we can replace some of PBT... 

Polyamide 6 is one of the well-known and oldest engineering thermoplastics, which has many uses in the transportation, automotive, apparel and sports industries due to its high strength, high corrosion resistance and high service temperatures. Cite gears, radiator tank, cylinder head cap and fuel rails can be mentioned as Polyamide 6 applications in the automotive industry. Glass fibers are used as reinforcement in PA6 media in order to enhance mechanical properties like tensile and impact strength. Even though the glass fiber improves the mechanical properties of the components produced from fiber-reinforced composites, it increases the anisotropy properties of the material and making it... 

Metallic glasses have been applied in industry owing to their attractive mechanical, physical, and chemical properties. such as high electrical resistivity, soft-type superconductivity, good magnetic softness, high strength and large elastic strain. These unusual properties make the amorphous alloys potentially useful for various applications, which originate from the intrinsic random atomic configuration. but their plasticity is low and this disadvantage limites their applicable range as a engineering material. In this study we try to improve plasticity of metallic glasses by structural rejuvenation. Structural rejuvenation in metallic glasses by a thermal process (i.e. through recovery... 

In this work, friction stir welding of aluminum to magnesium sheets using alumina and zinc powders was investigated. A preliminary investigation has been carried out on the joining of aluminum 5052 to AZ61 magnesium alloys and finding the optimum welding parameters. The optimum parameters were found to be with the shoulder diameter, pin diameter, and pin height of 14 mm, 5 mm, and 2.7 mm, respectively, with the travel speed of 60 mm/min and rotating speed of 500 rpm. As regards the main purpose of the using zin and alumina powders are controlling of Al-Mg IMCs formation and benefiting from pinning effect of grain boundaries, hence by adopting preliminary investigations and fixing pervious...