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Title: Effect of Aging on Microstructure and Mechanical Properties of Aluminum Alloy 6082 Processed by Friction Stir Processing
Authors: Fahad Taysir Asi 
Supervisor: Dr. Khaled Al-Fadhalah
Keywords: Microstructure : Mechanical
Issue Date: 2018
Publisher:  Kuwait university - college of graduate studies
Abstract: Friction stir processing (FSP) has been used in the last decade as an effective surface modification method on several metallic alloys, and in particular aluminum alloys. The heat input caused by the friction between the tool shoulder and the surface of the material, as well as the rotational (stirring) action of the tool pin, modifies the microstructure of the alloy surface. Consequently, this microstructure modification results in grain refinement and enhancement of the mechanical properties. In this thesis work, it has been aimed to examine the effect of post artificial aging on the microstructural development and mechanical properties of aluminum alloy AA6082 subjected to FSP. Aging was conducted at three different temperatures (150, 175 and 200 oC) for a period of 1, 6 and 12 hours. Optical Microscopy (OM), Electron Back- Scattered Diffraction (EBSD), and X-ray Diffraction (XRD) were utilized to analyze the evolution of the microstructure. FSP produced fine equiaxed grains (6.5 m) in the stir zone (SZ) due to dynamic recrystallization. Unexpectedly, applying post aging resulted in additional refinement to the dynamically recrystallized grains due to the occurrence of recovery and recrystallization with increasing either aging temperature and/or aging time. An optimum average grain size of 3-4 m was obtained in the SZ by applying aging at 175 oC. This was accompanied by an increase in the fraction of high-angle grain boundaries. In addition, the microhardness of the SZ was evaluated by using Vickers microhardness. FSP resulted in a reduction in the SZ microhardness due to the dissolution of the hardening precipitates. Compared to other aging temperatures, aging at 175 oC was shown to present the maximum hardness recovery (90 Hv) to the initial value of base metal (92 Hv). Such recovery is most likely attributed to the uniform distribution of fine precipitates in the SZ with increasing aging time to 12 hours.
Appears in Programs:0630 Mechanical Engineering

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