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Microstructural characteristics and mechanical properties of Al-2024 alloy processed via a rheocasting route

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International Journal of Minerals,Metallurgy and Materials 2015年第1期22卷 59-67页

作者： Behnam Rahimi hamed khosravi Mohsen Haddad-Sabzevar Department of Metallurgy and Materials Engineering Faculty of EngineeringFerdowsi University of Mashhad Faculty of Materials Science and Engineering K.N.Toosi University of Technology

This article reports the effects of stirring speed and T6 heat treatment on the microstructure and mechanical properties of Al-2024 alloy synthesized by a rheocasting process. There was a decrease in grain size ofα-Al particles corresponding to an increase in stirring speed. By increasing the stirring speed, however, the globularity of matrix particles first increased and then declined. It was also found that the hardness, compressive strength, and compressive strain increased with the increase of stirring speed. Microstructural studies revealed the presence of nonsoluble Al15（CuFeMn）3Si2 phase in the vicinity of CuAl2 in the rheocast samples. The required time for the solution treatment stage was also influenced by stirring speed;the solution treatment time decreased with the increase in stirring speed. Furthermore, the rheo-cast samples required a longer homogenization period compared to conventionally wrought alloys. Improvements in hardness and compres-sive properties were observed after T6 heat treatment.

关键词： aluminum alloys rheocasting microstructure mechanical properties

Correlation between microstructural features and tensile strength for friction welded joints of AA-7005 aluminum alloy

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Journal of Central South University 2016年第8期23卷 1839-1846页

作者： Seyyed Mostafa Tahsini Ayyub Halvaee hamed khosravi School of Metallurgy and Materials Engineering College of Engineering University of Tehran Department of Materials Engineering Faculty of Engineering University of Sistan and Baluchestan

Similar friction welded joints of AA-7005 aluminum rods were fabricated using different combinations of process parameters such as friction pressure(1.0, 1.5 and 2.0 MPa) and friction time(10, 15 and 20 s). Interfacial microstructure and formation of intermetallic compounds at the joint interface were evaluated via scanning electron microscopy(SEM) equipped with energy dispersive spectrum(EDS), and optical microscopy(OM). Microstructural observations reveal the formation of intermetallic phases during the welding process which cannot be extruded from the interface. Theses phases influence the tensile strength of the resultant joints. From the tensile characteristics viewpoint, the greatest tensile strength value of 365 MPa is obtained at 1.5 MPa and 15 s. Finally, the role of microstructural features on tensile strength of resultant joints is discussed.

关键词： friction welding AA-7005 aluminum alloy microstructure intermetallics tensile strength

Effects of compocasting process parameters on microstructural characteristics and tensile properties of A356-SiC_p composites

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Transactions of Nonferrous Metals Society of China 2014年第8期24卷 2482-2488页

作者： hamed khosravi hamed BAKHSHI Erfan SALAHINEJAD Faculty of Materials Science and Engineering K.N. Toosi University of Technology

The effects of compocasting process parameters on some structural and tensile characteristics of the A356-10% SiCp (volume fraction) composites were studied. Semisolid stirring was carried out at temperatures of 590, 600 and 610 °C with stirring speeds of 200, 400 and 600 r/min for 10, 20 and 30 min. The distribution of the SiC particles within the matrix, porosity content and tensile properties of the obtained samples were examined. The structural evaluations show that by increasing the stirring time and decreasing the stirring temperature, the uniformity in the particle distribution is improved;however, by increasing the stirring speed the homogeneity firstly increases and then declines. It is also found that by increasing all of the processing parameters, the porosity content is enhanced. From the tensile characteristics viewpoint, the optimum values of the speed, temperature and time are found to be 400 r/min, 590 °C and 30 min, respectively. The contribution of the reinforcement distribution uniformity prevails over that of the porosity level to the tensile properties.

关键词： A356-SiC_p composite semisolid stirring compocasting porosity reinforcement distribution tensile properties

Modeling and optimization of cooling slope process parameters for semi-solid casting of A356 Al alloy

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Transactions of Nonferrous Metals Society of China 2014年第4期24卷 961-968页

作者： hamed khosravi Reza ESLAMI-FARSANI Mohsen ASKARI-PAYKANI Department of Materials Engineering Faculty of Mechanical EngineeringK. N. Toosi University of Technology School of Metallurgy and Materials Engineering College of EngineeringUniversity of Tehran

Semi-solid processing （SSP） of A356 aluminum alloy was discussed via cooling slope （CS） method. The D-optimal design of experiment （DODE） was employed for experimental design and analysis of results. 38 random experiments obtained by software were carried out. In experimental stage, the molten aluminum alloy was poured on an inclined plate with different lengths of 100, 300 and 500 mm set at 30°, 45° and 60° of slope angles respectively. Three different pouring temperatures of 660, 680 and 700 ℃ were also used. After the casting process, the partial re-melting treatment was carried out at 590 ℃ for different isothermal time of 5, 8 or 12 min. The combined effect of these factors on globularity of the primary α（Al） crystals was investigated and optimized using DODE. The results indicated that the primary dendritic phase in the conventionally cast A356 alloy was transformed into a non-dendritic one in ingots cast over a cooling plate. The CS processed samples exhibited a globular structure only after re-heating to semi-solid region. The optimum values of pouring temperature, cooling length, slope angle and isothermal holding time were found to be 660 ℃, 360 mm, 48°, and 9 min, respectively. In this case, the globularity of primary crystals was obtained, about 0.91. The obtained model is highly significant with a correlation coefficient of 0.9860.

关键词： vA356 aluminum alloy cooling slope process modeling D-optimal design of experiment