Sharif Digital Repository

Taking advantage of aluminum and its alloys in industry is increasing. A common method in metal forming is hot forming. In this condition a precise prediction of flow behaviour of the alloy is necessary to achieve a product of desirable mechanical and physical properties. In this situation, influence of parameters such as chemical composition, temperature, strain, strain rate as well as recovery and recrystallization phenomena should be considered and by using a suitable model, the metal behavior prediction is possible. Distribution of coherent Al3Sc dispersoids in high volume fraction accompany with Al6Mn result in strengthening to this alloy. Because of the high stacking fault energy,... 

Splitting in ingot cast structures and transverse cracks in continuous cast structures are the main problems of hot rolling of low carbon resulfurized free-cutting (LCRF) steels. Presence of high volume fraction of manganese sulfide inclusions in cast structure increases the risk of alligatoring in hot rolling. Because of high sulfur content of these steels and probability of formation of low melting point phases, minimum level of manganese and maximum level of copper and tin is necessary. Morphology of manganese sulfide is another important factor in hot forming of these steels, which can be controlled by level of deoxidation in steel making. In fact, MnS2 is present in fully killed... 

Fe-29Ni-17Co alloy with commercial name “Kovar” is an alloy with low expansion coefficient. The main specification of this alloy is to maintain this property at the high temperatures that is used in sealing of glass-metal. Achieving to desirable physical properties associated with suitable mechanical properties is the purpose of related industries. However the effect of cold work and heat treatment was studied on the physical properties of this alloy, there is no report about the effect of the hot work. Thus, in this investigation, the effect of the hot work on the physical and mechanical properties of Kovar was studied. At first, slabs of Kovar alloy were cast and remelted. Then,... 

Since the increase in the strength of metals resulting from the severe plastic deformation (SPD) leads to a reduction in their ductility, recently, several studies have been carried out on the deformation of metals. One if the goals has been increasing the ductility while maintaining the strength. In this project, copper is undergone severe plastic deformation in a constrained groove pressing (CGP) process. According to previous studies, it has been determined that with an optimal annealing process, not only the strength is not decreased, but also it is slightly increased and also the ductility is enhanced. Thus, in order to improve the surface of copper after CGP and also optimize its... 

The A-286 superalloy is an iron-nickel base alloy having properties such as oxidation resistance and high mechanical strength. In addition, good producibility and high workability are the important properties of this alloy. In the present work dynamic restoration mechanism of A-286 supper alloy during thermo-mechanical processing has been studied. The aim is to verify the dominant restoration mechanism in different deformation conditions and also to determine the desire deformation parameters for hot rolling. In this regard, utilizing compression test in the range of 950 to 1100ºC and strain rate of 0.001 to 1 per second, the strain-stress curve for this alloy was obtained. After correction... 

Aluminum alloys are widely used in many applications in aerospace and automotive industries. Therefore, the study of the effects of different parameters such as chemical composition, temperature, strain, strain rate and recovery and recrystallization phenomena being more effective on controlling of microstructure and final properties of product, are more important. In this research, deformation behavior of AlMg6 alloy has been studied from two theoretical and experimental views as described below: In ambient temperature deformation, the mechanical properties in correlation on the microstructures developed at different temperatures have been assessed. The results of tensile test demonstrated... 

Lightweight aluminum and magnesium alloy sheets do not generally possess as much strength as steel sheets and their strength need to be increased by a suitable process such as Accumulative Roll Bonding (ARB). One of the most important limitations of ARB is the low ductility and formability of the sheets produced by this process. In the present research conducted on the 5083 aluminum and AZ31 magnesium alloy sheets efforts have beem made to overcome this limitation by heating up the sheets whether during metal forming process as hot deformation or as distinct controlled annealing process subsequent to the deformation, in order to develop the application domain of the sheets. Results... 

In this study, the high temperature deformation behavior of Al-Cu aluminum alloy and the results of single-stage and multi-stage creep tests have been investigated. To investigate the behavior of alloy fluidity in temperature range 150 ° C to 500 ° C and strain rate 0.0005 s-1 – 0.05 s-1 were subjected to tensile test. The results show that in the temperature range of 200 ° C to 225 ° C, the sensitivity coefficient to the strain rate is negative, which indicates the occurrence of dynamic precipitation during deformation. In the meantime, the reverse processes in the mentioned temperature range were investigated and it was found that 250 ° C was the starting temperature of the dynamic... 

In this work, the deformation behavior of an Aluminium-Magnesium alloy i.e. AA5052, in different temperature ranges was studied experimentally and theoretically. For this purpose, uniaxial tensile tests were carried out in the temperature range of 25°C to 450°C and under strain rates of 0.001 "s-1" to 0.05 "s-1" . Also, the occurrence of dynamic strain aging and dynamic softening mechanisms of the alloy were taken into account. It was observed that the dynamic strain aging occurred in the temperature range of 25°C to 125°C while the corresponding activation energy was defined as 46.2 kJ/mol which is close to migration of Mg atoms in aluminum. At hot deformation region, different softening... 

The 2024 aluminum alloy is deformed by two passes of multi-directional forging at room temperature, 180 oC, 250 oC, 320 oC and 380 oC with initial state of solid solution. Microstructure, mechanical properties and the state of precipitates are investigated via optical and scanning electron microscopies, hardness test, shear punch test and differential scanning calorimetry. Fragmentation and distribution of the precipitates are observed after straining at different temperatures. Dynamic precipitation of GPB zones at room temperature and 180 oC are studied by DSC analysis. The increase of both hardness and strength and the formation of shear bands are related to the presence of GPB zones.... 

Magnesium and its alloys have gained much attention in medical applications, especially bio-degradable stents. However, they have not been used extensively due to their natural limitations, such as weak mechanical properties. WE43 magnesium alloy has gained attention as a bio-alloy due to its high temperature and good corrosion resistance. The present study aims to use a combination of ECAP and direct tube extrusion to fabricate thin wall tubes with good mechanical properties using WE43 magnesium alloy. In the first phase, the ECAP process at 370°C were conducted up to 4 passes on the homogenized samples to reach ultrafine grain structure. Subsequent to ECAP, direct tube extrusion at 230 °C,... 

In recent years, various research has been done on the severe deformation of low carbon steel sheets. One of the methods used is the pressing in the grooved die, only two passes of the pressing process in the grooved mold have been successful when applied to these sheets, but on the other hand, these two passes also lessen the sheet's ductility while increasing its strength. Due to the fact that the sheet surface produced by the pressing in the grooved die is not entirely smooth, the attempt in this project was to improve the ductility to some extent using warm rolling in addition to the smoothness of the surface using higher temperature while improving the strength or maintain it. To... 

Magnesium and its alloys have gained significant attention in medical applications due to their good biocompatibility. However, their widespread use has been limited by some inherent drawbacks, such as poor mechanical properties. The ZX00 magnesium alloy has been used in medical applications, including implants, due to its slow degradation rate and good ossification. However, this alloy lacks sufficient strength and ductility. The severe plastic deformation method can create an ultrafine grain structure and improve mechanical properties. In this study, to improve the mechanical properties and create an ultrafine grain structure, the multi-directional forging process was performed on... 

Nowadays, the application of magnesium alloys as biodegradable implants in the medical industry has garnered significant attention. However, the low mechanical properties and rapid degradation rate of pure magnesium implants in the biological environment have hindered their widespread use for clinical applications. Magnesium-calcium alloys, due to their low degradation rate and promotion of faster bone healing, have become attractive choices for orthopedic applications. Nevertheless, the micro alloy X0 used in this study lacks sufficient strength and flexibility, limiting its potential applications. Utilizing severe plastic deformation methods to create ultrafine microstructures can greatly...