Aluminum forging products has been increasingly used in automotive and aerospace industry due to their lightness and strength. In this study, aluminum forging processes of a particular industrial part for the two different alloys (Al 7075 and Al 6061) have been analyzed. The forging part, forging process and the required dies have been designed according to the aluminum forging design parameters. The proposed process has been simulated by using the Finite Volume Method. In the simulations, analysis of the part during forging process has been performed / and the required forging force, the temperature distribution and the effective stress distribution in the parts have been obtained. The forging dies were produced in the METU-BILTIR Center CAD/CAM Laboratory. The experimental study has been performed in the METU-BILTIR Center Forging Research and Application Laboratory. The parts were produced without any defects as obtained in the finite volume simulations. The results of the experiment and finite volume simulation are compared and it has been observed good agreement.

Aerospace Engineering / The aim of this thesis is to explore the high strain rate behavior of metallic specimens using electromagnetic inductive loading as the means to inflict the required high strain rate deformation on laboratory scale specimens, allowing for controlled, repeatable experiments to be performed. Three separate experiments were designed and performed, using helical and spiral coils as the sources of radial and unidirectional loading. The first experiment evaluated the effect of applying a polymer coating on 30.5 mm diameter, Al 6061- O tube samples, in two lengths, 18 and 36 mm. The expanding tube experiment was used to apply a radial loading on the specimens and record the event. Several optical techniques were then used to evaluate the behavior of the samples. Coatings of polyurea and polycarbonate were used. It was observed that the polycarbonate coating seemed to have a more profound effect on the behavior of the metal, by applying a larger restraining pressure on the tube surface during the expansion process, and thereby modifying the stress state of the specimen. The second experiment looked to design an experimental arrangement to test the plane strain, high strain rate behavior of Al 6061-O tubes of different lengths. A 112 mm long solenoid was designed and manufactured, and testing was performed on 30.5 mm diameter Al 6061-O tubes in lengths of 50, 70 and 90 mm. It was observed that the coil behaved similar to shorter ones at low voltages and that the longer the specimen used, the more its deformation path approached a plane strain condition. Finally, a third experiment was performed to develop an experiment to accelerate a plate to high linear velocities, as a means to evaluate the use of a flat spiral coil as the driver for future experiments based upon electromagnetic inductive loading. A prototype coil was manufactured and installed into a converted expanding tube experimental setup. Three samples were tested in several sizes, and materials: aluminum and steel. Speeds in the range of 45 to 251 m/s were obtained, validating the apparatus as a viable method to provide a unidirectional loading. / text

The Cold-Gas Dynamic-Spray process also known as Cold Spray (CS) has been researched for three decades. The CS process is a solid-state deposition technique via supersonic velocity of powder particles at a temperature significantly below the melting point of the spray material. This thesis presents background on the overall CS process parameters, and additional information on the microstructural and mechanical properties of typical Cold Sprayed materials.This Thesis primarily presents a study on the microstructural annealing response of CS Al 6061. It should be noted that for this study, the term “annealing” is used in the sense of the classical metallurgical definition of annealing, and not a specific temper designation for the 6061 alloy. Cross sections of CS Al 6061 were imaged with a scanning electron microscope (SEM) in secondary electron (SE), backscatter electron (BSE), and electron backscatter diffraction (EBSD) imaging mode for quantitative and qualitative information on the grain size and orientation of the CS microstructure. The detailed SE, BSE and EBSD mode images present the grain size and grain orientation of the original powder, as received (AR) state and after heat treating at 200°C for 1 hour, 10 hours, and 100 hours. Three different regions, characterized with distinctly differing microstructures, are labeled as low, medium, and high deformation regions, and their microstructures, and evolving features are discussed. Vickers microhardness testing are performed to examine the differences in hardness values between different heat treatments, and for correlation with the level of deformation and grain refinement in the microstructure. SEM imaging was used in BSE mode to correlate microhardness variation to the different regions within the CS microstructure.

Industrial products of high-strength Al-alloys are currently manufactured by thermo-mechanical processes, which are only applicable in the integrated plants requiring high investment cost. Moreover, reduction of the average grain size not less than 10 &mu / m and re-adjustment of process parameters for each alloy type is evaluated as disadvantage. Therefore, recently there have been many research studies for development of alternative manufacturing techniques for aluminum alloys. Research activities have shown that it is possible to improve the strength of Al-alloys remarkably by severe plastic deformation which results in ultra-fine grain size. This study aims to design and manufacture the laboratory scale set-ups for severe plastic deformation of aluminum alloys, and to characterize the severely deformed samples. The stages of the study are summarized below: First, for optimization of die design and investigation of parameters affecting the deformation finite element modeling simulations were performed. The effects of process parameters (die geometry, friction coefficient) and material properties (strain hardening, strain-rate sensitivity) were investigated. Next, Equal Channel Angular Pressing (ECAP) system that can severely deform the rod shaped samples were designed and manufactured. The variations in the microstructure and mechanical properties of 2024 Al-alloy rods deformed by ECAP were investigated. Finally, based on the experience gained, a Dissimilar Channel Angular Pressing (DCAP) system for severe plastic deformation of flat products was designed and manufactured / then, 6061 Al-alloy strips were deformed. By performing hardness and tension tests on the strips that were deformed by various passes, the capability of the DCAP set-up for production of ultra-fine grain sized high-strength aluminum flat samples were investigated.