MODELING HIGH TEMPERATURE FLOW BEHAVIOR OF AN AL 6061 ALUMINIUM ALLOY

Hot deformation behavior of a medium Cr/Mn Al6061 aluminum alloy was studied by isothermal compression test at temperatures range of 320 to 480 °C and strain rates range of 0.001 to 0.1 s −1. The true stresstrue strain curves were analyzed to characterize the flow stress of Al6061. Plastic behavior, as a function of both temperature and strain rate for Al6061, was also modeled using a hyperbolic sinusoidal type equation. For different values of material constant α in the range of 0.001 to 0.4, values of A, n and Q were calculated based on mathematical relationships. The best data fit with minimum error was applied to define constitutive equation for the alloy. The predicted results of the proposed model were found to be in reasonable agreement with the experimental results, which could be used to predict the required deformation forces in hot deformation processe

INFLUENCE OF CARBON ON THE AGEING BEHAVIOUR OF TI-13V-11CR-3AL

The effect of aging time and temperature on the microstructure and mechanical properties of Ti-13V-11Cr-3Al and Ti-13V-11Cr-3Al-0.2C was studied. The carbon addition increases the rate of age hardening as well as the peak hardness of aged samples. The presence of titanium carbides in Ti-13V-11Cr-3Al-0.2C limits grain growth during the process. The observations in this work are discussed in terms of the effect of the microstructural changes in quenched and aged samples associated with the presence of carbide precipitate

DISLOCATIONS STRUCTURE AND SCATTERING PHENOMENON IN CRYSTALLINE CELL SIZE OF 2024 AL ALLOY DEFORMED BY ONE PASS OF ECAP AT ROOM TEMPERATURE

Variation in microstructural features of 2024 aluminum alloy plastically deformed by equal channel angular pressing (ECAP) at room temperature, was investigated by X-Ray diffraction in this work. These include dislocation density dislocation characteristic and the cell size of crystalline domains. Dislocations contrast factor was calculated using elastic constants of the alloy such as C 11, C 22 and C 44 . The effect of dislocations contrast factor on the anisotropic strain broadening of diffraction profiles was considered for measuring the microstructural features on the base of the modified Williamson-Hall and Warren-Averbach methods. Results showed that the dislocations density of the solution annealed sample increased from 4.28×10 12m-2 to 2.41×10 14m-2 after one pass of cold ECAP and the fraction of edge dislocations in the solution annealed sample increased from 43% to 74% after deformation. This means that deformation changed the overall dislocations characteristic more to edge dislocations. Also the crystalline cell size of the solution annealed sample decreased from 0.83μm to about 210nm after one pass of ECAP process at room temperatur

Prediction of Temperature Distribution in the Hot Torsion Test Specimen

Hot torsion test (HTT) has extensively been used to analysis and physically model flow behavior and microstructure evolution of materials and alloys during hot deformation processes. In this test, the specimen geometry has a great influence in obtaining reliable test results. In this paper, the interaction of thermal-mechanical conditions and geometry of the HTT specimen was studied. The commercial finite element package ANSYS was utilized for prediction of temperature distribution during reheating treatment and a thermo-rigid viscoplastic FE code, THORAX.FOR, was used to predict thermo-mechanical parameters during the test for API-X70 micro alloyed steel. Simulation results show that no proper geometry and dimension selection result in non uniform temperature within specimen and predicted to have effects on the consequence assessment of material behavior during hot deformation. Recommendations on finding proper specimen geometry for reducing temperature gradient along the gauge part of specimen will be given to create homogeneous temperature as much as possible in order to avoid uncertainty in consequent results of HTT

Process Control Strategies for Dual-Phase Steel Manufacturing Using ANN and ANFIS

In this research, a comprehensive soft computational approach is presented for the analysis of the influencing parameters on manufacturing of dual-phase steels. A set of experimental data have been gathered to obtain the initial database used for the training and testing of both artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS). The parameters used in the strategy were intercritical annealing temperature, carbon content, and holding time which gives off martensite percentage as an output. A fraction of the data set was chosen to train both ANN and ANFIS, and the rest was put into practice to authenticate the act of the trained networks while seeing unseen data. To compare the obtained results, coefficient of determination and root mean squared error indexes were chosen. Using artificial intelligence methods, it is not necessary to consider and establish a preliminary mathematical model and formulate its affecting parameters on its definition. In conclusion, the martensite percentages corresponding to the manufacturing parameters can be determined prior to a production using these controlling algorithms. Although the results acquired from both ANN and ANFIS are very encouraging, the proposed ANFIS has enhanced performance over the ANN and takes better effect on cost-reduction profit

Physical simulation of hot deformation and microstructural evolution for 42CrMo4 steel prior to direct quenching

Direct quenching and tempering (DQ-T) of hot rolled steel section has been widely used in steel mill for the sake of improvement of mechanical properties and energy saving. Temperature history and microstructural evolution during hot rolling plays a major role in the properties of direct quenched and tempered products. The mathematical and physical modeling of hot forming processes is becoming a very important tool for design and development of required products as well as predicting the microstructure and the properties of the components. These models were mostly used to predict austenite grain size (AGS), dynamic, meta-dynamic and static recrystallization in the rods immediately after hot rolling and prior to DQ process. The hot compression tests were carried out on 42CrMo4 steel in the temperature range of 900–1 100 °C and the strain rate range of 0. 05–1 s−1 in order to study the high temperature softening behavior of the steel. For the exact prediction of flow stress, the effective stress-effective strain curves were obtained from experiments under various conditions. On the basis of experimental results, the dynamic recrystallization fraction (DRX), AGS, hot deformation and activation energy behavior were investigated. It was found that the calculated results were in good agreement with the experimental flow stress and microstructure of the steel for different conditions of hot deformation

Simulation of deformation and fracture initiation during equal channel angular pressing of AZ31 magnesium alloy with covered tube casing

The present research was aimed at lowering the deformation temperature by applying cover tube casing (CTC) to AZ31 magnesium alloy samples subjected to equal channel angular pressing (ECAP) without triggering surface defects and/or fracture. The Cockcroft-Latham (C & L) fracture model was incorporated into finite element simulation and the critical values for a fracture to occur were determined. The fracture was predicted for the samples deformed at 150, 175, and 200 °C without CTC and with CTC having thicknesses of 1 and 4 mm. The predictions of the model were verified with experimental data. It was found that the workability of AZ31 increased with increasing CTC thickness, as a result of a reduction in the maximum principal stress at the top surface, a uniform distribution of strains, and an increase in the critical damage. In practice, the use of CTC led to the possibility of a reduction in deformation temperature by 25 °C. A sound product with a homogeneous grain structure and a mean grain size of 11 μm was achieved at 175 °C. Thus, the ECAP working window for the alloy was enlarged with accompanying benefits in energy consumption, tooling life, and manufacturing costs.Biomaterials & Tissue Biomechanic

Modern fiber laser beam welding of thenewly-designed precipitation-strengthened nickel-base superalloys

In thepresentresearch,themodern fiber laserbeamweldingofnewly-designedprecipitation- strengthened nickel-basesuperalloysusingvariousweldingparametersinconstantheatinputhasbeen investigated.Fivenickel-basesuperalloyswithvariousTiandNbcontentsweredesignedandproduced by VacuumInductionMeltingfurnace.The fiber laserbeamweldingoperationswereperformedin constant heatinput(100Jmm2) anddifferentweldingpowers(400and1000W)andvelocities(40and 100mms1) using6-axisanthropomorphicrobot.Themacro-andmicro-structuralfeatures,weld defects, chemicalcompositionandmechanicalpropertyof3.2mmweldmentswereassessedutilizing optical andscanningelectronmicroscopesequippedwithEDSanalysisandmicrohardnesstester.The results showedthatweldingwithhigherpowerscancreatehigherpenetration-to-widthratios.The porosity formationwasincreasedwhentheweldingpowersandvelocitieswereincreased.Noneofthe welds displayedhotsolidification andliquationcracksin400and1000Wweldingpowers,butliquation phenomenon wasobservedinalltheheat-affectedzones.WithincreasingtheNbcontentofthe superalloystheliquationlengthwasincreased.Thechangingoftheweldingpowerandvelocitydidnot alter thehardnesspropertyofthewelds.ThehardnessofweldsdecreasedwhentheTicontentdeclined in thecompositionofsuperalloys.Finally,the400and1000W fiber laserpowerswithvelocityof40and 100mms1 havebeenofferedforhotcrack-freeweldingofthethinsheetofnewly-designed precipitation-strengthenednickel-basesuperalloys