In this study, the effects of passes number and cooling during friction stir processing (FSP) on the microstructure and properties of AZ31 magnesium alloy has been investigated. The process was carried out at tool rotational speed, transverse speed and tool tilt angle of 1100 rpm, 52 mm/min, and 3°, respectively. Cooling was performed by water. The microstructure of FSPed samples was explored by optical microscopy, atomic force microscope (AFM), and scanning electron microscope (SEM). Microhardness and tensile tests were used to characterize the mechanical properties of the samples. In addition, wear and corrosion resistance of processed samples were evaluated. Microstructural investigations showed that the cooling process during FSP led to finer and more homogenized grains because of the suppression of grain growth and as a result, hardness and tensile strength were improved. The best properties obtained after 4 passes by an increase in hardness and tension strength equal to 57 and 21%, respectively. In addition, wear characteristics of this specimen was considerably improved and electrochemical tests showed better corrosion resistance due to the decreasing grain size. پرونده مقاله

In the present study, Al5083- Al2O3 nanocomposite was successfully prepared by friction stir processing (FSP) with rotational speed of 710 rpm and travel speed of 14 mm/min. In order to improve distribution of Al2O3 particles, a net of holes were designed on the surface of Al5083 sheet. The samples were characterized by optical and scanning electron microscopy (SEM), microhardness, tensile and wear tests. Results showed that FSP is an effective process to fabricate Al5083- Al2O3 surface nanocomposite. Microstructural observation demonstrated fine and equiaxed grains and homogenous distribution of Al2O3 nanoparticles in the stir zone (SZ). The presence of Al2O3 nanoparticles lead to a decrease in the grain size from 45 to 7 μm and an increase in microhardness from 80 to 140 Hv and tensile strength from 280 to 335 MPa. Wear test results showed improved wear resistance due to its higher hardness and the mode of wear in the all samples was abrasive. پرونده مقاله