Sharif Digital Repository

The stiffness rate of the 300 series austenitic stainless steel has long been known to depend on the stability of the austenite and its susceptibility to martensite formation. In this project, the cold deformation of austenitic stainless steel (304L) and the occurrence of martensite deformation during it are studied. Experimental cold rolling experiments under different strain velocities and initial temperatures in the range of -10° C to 25° C; Performed and microstructure, mechanical properties and percentage of martensite generated in rolled steel are determined and evaluated employing different testing techniques. mathematical modeling of cold rolling operation is also performed using... 

In this research, the effects of natural and artificial aging heat treatments on the mechanical and wear behavior of an aluminum alloy from the 7xxx series have been investigated. The study commenced with annealing of the received samples, which were subsequently divided into four categories. One of these categories was placed in a freezer as annealed samples, while the other two underwent artificial aging heat treatments at temperatures of 180 and 210 degrees Celsius. The final category naturally aged over time. As a result, different structures with varied distributions and morphologies of precipitates were formed, and the mechanical properties, mechanisms, and wear resistance of the... 

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... 

Nowadays, Thermomechanical processes are used to change the microstructure and create desirable mechanical properties in metals. In this research, with the aim of improving the mechanical properties and formability of 7000 series aluminum alloys, the Cyclic Quench-Rolling (CQR) process was designed and investigated as a new thermomechanical process with solid solution strengthening mechanism. First, for solution heat treatment, the 7075-T6 aluminum sheet was placed in the oven at 460 °C for 5 hours and quenched in water. After making the solid solution, in each cycle of CQR, a rolling step was performed, then intermediate solutioning heat treatment and then quenching was performed. To study... 

In this study, thermo-mechanical behavior of an austenitic stainless steel AISI316L was investigated using mathematical modeling and experimental analysis during warm rolling process. First, the thermo-mechanical analysis was carried out employing the finite element software, Abaqus CAE, to assess temperature, strain, velocity and stress distribution during rolling. Then, rolling operations on 316L austenitic steel were performed under different working conditions while mechanical testing as well as microstructural observations were made on the rolled steels. Using simulation results and practical data, microstructural events and mechanical properties after warm rolling of stainless steel... 

In this research, the hot and warm rolling of stainless steel 304 was studied. First the rolling process was simulated using Finite Element Method software ABAQUS and the distribution of temperature and strain in the process under discontinuous conditions were predicted. Next, hot and warm rolling of stainless steel 304 under different conditions was carried out. Specimens were cut and subject to mechanical testing, metallography and electron microscopic studies. Data obtained from these experiments and the predicted trends from ABAQUS were compared, therefore studying the effect of different parameters on the microstructure and mechanical properties of the rolled specimen. Results indicate... 

A mathematical model was developed to assess thermomechanical behavior of work rolls during warm rolling processes of AA2017. A combined finite element analysis-slab method was first developed to determine thermal and mechanical responses of the strip being rolled under steady-state conditions; Then, the calculated roll pressure and temperature field were utilized as the governing boundary conditions for the thermomechanical problem of the work roll. Finally, the thermomechanical stresses within the work rolls were predicted by a thermoelastic finite element approach. The results indicate that, in warm strip rolling, thermal and mechanical stresses developed in the work rolls are comparable.... 

In this research, temperature distribution and roll force during steady state warm and hot rolling of 6061 Al alloy strip have been simulated, using finite element method and upper bound solution. At first, the velocity field and deformation zone shape have been determined, by means of upper bound solution, then using 2D finite element method, the temperature distribution within rolling and considering rate of heat of deformation, has been calculated. This model generalized for two pass steady state warm and hot rolling. Also, in order to evaluate the predictions, the experimental recorded of temperature variation, during hot rolling and temperature variation predicted by model has been... 

In this study, transformation of austenite to ferrite under continuous cooling condition of a low carbon steel was investigated. In the first step, a heat transfer model was employedconsidering governing heat transfer boundary conditions and a microstructure model based on Cellular Automaton method was used simultaneouslyto predict austenite to ferrite transformation progress. The influence of pre-heating temperature and primary austenite grain size on the final ferrite grain size and distribution were perdected. To verify the simulation results, experimental processes were utilized. The microstructure distribution was determined by means of Clemex Pro software then, these results were... 

Austenite in the 300 stainless steels is not a table phase in deformation processing during which martensite phase forms. This causes significant changes in the microstructures as well as the mechanical properties of deformed steel. In this work, the effects of rolling speed, reduction, temperature and strain pass on the strain-induced martensite during strip rolling operation of stainless steel 304L are studied. Cold rolling experiments under different speeds, reduction and temperature are conducted and then, the microstructural events and mechanical properties of the rolled steel are evaluated. For doing so, different testing techniques including tensile test, hardness measurement, optical... 

In this work, annealing procedure of cold-deformed AA5052-SiC composite has been simulated by using cellular automata approach and the effect of SiC second phase on softening kinetics has been studied. To do so, site saturated nucleation has been employed to establish initial microstructure. In addition, topological changing due to deformation has been implemented on the microstructure. During annealing, recovery and recrystallization phenomena occur simultaneously, and it has strong effect on the annealed microstructure. Therefore, during annealing, recrystallization and recovery has been considered simultaneously and decreasing in the stored energy, which has developed during deformation... 

A mathematical model has been proposed to estimate the deformation pattern and the required power in cold plate rolling using the stream function method and upper bound theorem. In the first place admissible velocity distributions as well as the geometry of deformation zone were derived from the proposed stream functions. Then, the optimum velocity field was obtained by minimization of the power function computed based on the upper bound theorem. Then a steady state heat transfer equation has been solved in whole model using finite element method. In order to verify the predictions, rolling experiments on aluminum plates were conducted and also, a finite element analysis performed employing... 

Static recrystllization in low carbon steel after two type of deformation –sidepress as an inhomogeneous deformation and rolling as a common industrial process - has been simulated using Cellular Automata (CA). The finite element method was utilized to compute the strain and stored energy distribution due to deformation. The initial microstructures were created by simulation of recrystallization with homogeneous site-saturated nucleation and topologic deformation was also considered in model. Subsequently using the result of FEM, stored energy of deformation was calculated and transferred into a two dimensional CA lattice. Nucleation rate and grain boundary velocity were considered... 

Mechanical behavior of aluminum-magnesium alloy, AA5083, was studied at high temperatures using hot tensile testing together with uniaxial creep experiments. In the first place, the as-received AA5083 sheet was subjected to annealing heat treatment to remove the effect previous plastic straining. Then, creep experiments were conducted at temperatures in the range of 190°C to 300 ° C under constant the stress varied between 30 MPa to 100 MPa. The hot tensile testing was also carried out from room temperatures up to 400 °C under nominal constant strain rates of 0.0005, 0.005, 0.01 and, 0.05 (1/s). In addition to the mechanical testing, optical metallography and scanning electron microcopy were... 

In this research, hot deformation and creep behavior of aluminum alloy i.e.AA2017 were taken into account while the impact of the initial microstructure of the examined alloy was also studied. In order to investigate the behavior of the alloy, tensile tests were conducted at temperatures ranging from 120°C to 400°C under the nominal strain rates of 0.0005 s-1, 0.005 s-1, 0.05 s-1. In these experiments, two different initial microstructures were employed including solution treated samples as well as artificially aged specimens. The results show that in the temperature range of 180°C to 250°C, the strain rate sensitivity parameter is negative in the solution treated samples which indicates... 

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 study, creep behavior and cavitation as well as high temperature deformation of Al-Zn-Mg aluminum alloy were investigated by means of uni-axial creep and tensile tests. The as-received material i.e. AA7075 plate, was first stabilized utilizing over-aging heat treatment and then stress-controlled creep tests were performed in the temperatures ranging between 120℃ to 210℃ under the applied stresses varying 130MPa to 250MPa. Accordingly, the stress exponent and creep activation energy were determined as 5.7 and 149kJ/mol.K to 189kJ/mol.K, respectively. Considering these parameters, it was found that the governing creep mechanism, in the mentioned temperature range, would be dislocation... 

In austenitic stainless steel types 304 and 316, due to the instability of the austenite phase, the martensite phase is formed by plastic deformation below the Md temperature. In this research, the cold rolling of 304L austenitic stainless steel and the transformation of austenite to strain-induced martensite and its effect on mechanical properties, especially wear, were studied. In this way, the samples were rolled in two modes and four passes in each mode. In the first case, the samples were cooled between each pass in water as a cooling liquid, and in the second case, the samples were cooled in each pass without using water and by air. Next, tests such as hardness measurement, uniaxial... 

In this study, the creep behavior of an Al-Cu alloy (AA2017) was investigated to examine mechanisms associated with cavitation, including cavity nucleation, growth, and coalescence, at intermediate temperatures. Initially, 2000-series aluminum alloy sheets underwent solution heat treatment at 495°C for 1 hour. Subsequently, the samples were subjected to artificial aging heat treatment at 210°C for 6 hours. Following the preparation process, creep tests were conducted within the temperature range of 120°C to 210°C and an applied stress range of 120 MPa to 290 MPa. Based on the stress exponent of 6.8 and activation energies of 169.9 kJ/mol and 194 kJ/mol obtained from the creep tests,...