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۱INFLUENCE OF PHOSPHORUS ADDITION ON THE MICROSTRUCTURE OF IN–SITU Al–25 WT.% Mg2Si COMPOSITE
اطلاعات انتشار: اولین همایش بین المللی و ششمین همایش مشترک انجمن مهندسی متالورژی ایران، سال
تعداد صفحات: ۱۱
In current research, the effects of different concentrations of P (0, 0.05, 0.1, 0.3, 0.5, 0.7 and 1 % wt.) on the microstructures of Al–25%wt. Mg2Si composite have been investigated. Microstructural examination was carried out by using optical and scanning electron microscopy (SEM). As–cast microstructure analysis of the composite indicated that the primary Mg2Si phases are very coarse with average size of 200μm. Also the results show that P addition changes the morphology of primary Mg2Sifrom irregular to polygonal or spherical shapes and decreases size of primary Mg2Si particles from200μm to 20 μm in 1%wt. added P specimen. Furthermore, the morphology of eutectic Mg2Si phases changes from fibriform to short fibriform or dot–like. With the addition of P, it reacts with Al to produce particles of AlP phase. The AlP particles can be appropriate sites for heterogeneous nucleation of Mg2Si. It is believed that P addition has strong influence on the nucleation process of primary Mg2Si particles and the subsequent formation of the α–Al phase and the eutectic matrix.<\div>

۲THE EFFECT OF Al–5Ti–1B AND Al–15Zr MASTER ALLOYS ON THE MICROSTRUCTURE AND TENSILE PROPERTIES OFEXTRUDED AA2014 Al ALLOY
اطلاعات انتشار: اولین همایش بین المللی و ششمین همایش مشترک انجمن مهندسی متالورژی ایران، سال
تعداد صفحات: ۱۲
This study was undertaken to investigate the effect of Al–5Ti–1B and Al–15Zr master alloys on the structural characteristics and tensile properties of extruded AA2014 aluminum alloy. The results revealed that the optimum Ti and Zr contents to achieve a fine–grained were found to be 0.03 wt.% and 0.5 wt.%, respectively. The average grain size decreased from 1000 μm to 162 μm and 203 μm,respectively with adding 0.03 wt.%Ti and 0.5 wt.% Zr. The results of tensile testing of the extruded specimens showed enhanced ultimate tensile strength (UTS) and elongation (%El) values of the 2014 alloy after Ti and Zr additions in optimum levels. Furthermore, with adding 0.5 wt.%Zr, tensile strength and elongation values of the extruded refined sample increased from 282 MPa and 12% to 379 MPa and17%, respectively. Also, with adding 0.03%Ti, tensile strength values of the extruded refined samplewere enhanced from 282 MPa to 370 Mpa, but elongation decreased from 12% to 8%. This could be attributed to uniform distribution of Al3Zr & Al3Ti particles in the α–Al matrix and the breakdown of Ɵ & S phases by applying of extrusion process<\div>

۳THE EFFECT OF HOT EXTRUSION ON TENSILE PROPERTIES OF Al– 25%Mg2Si COMPOSITE
اطلاعات انتشار: اولین همایش بین المللی و ششمین همایش مشترک انجمن مهندسی متالورژی ایران، سال
تعداد صفحات: ۱۰
Current study investigates the effect of hot extrusion on the microstructure and tensile properties of Al–25%Mg2Si composite by using optical microscopy and scanning electron microscopy (SEM). The small ingots were extruded at 520°C at extrusion ratio 6:1 and ram speed of 1mm\s. The microstructural studies of extruded samples by (SEM) revealed that the extrusion process changes the morphology of primary Mg2Si phase from irregular to polygonal or spherical shape. Further results demonstrated that the average size of primary Mg2Si decreases from 200μm to 50 μm after hot extrusion. Also, the ultimate tensile strength (UTS) and elongation values were increased from 108 MPa and 1.8% to 137 MPa and 2.3 %, respectively. Also, hot – extrusion can be due to the fragmentation of Mg2Si phases from continuously structure to dot–like structure, and lead to improvement in tensile properties<\div>

۴EFFECTS OF HOT EXTRUSION RATIO ON MICROSTRUCTURE OF Al – 25 WT.%Mg2Si IN–SITU METAL MATRIX COMPOSITE
اطلاعات انتشار: اولین همایش بین المللی و ششمین همایش مشترک انجمن مهندسی متالورژی ایران، سال
تعداد صفحات: ۷
This study was undertaken to investigate the effects of hot extrusion ratio on the microstructure of cast aluminum metal matrix composite (MMC) containing 25 wt.% coarse Mg2Siprimary particles. Different extrusion ratios (6:1, 12:1 and 18:1) were applied on the small cast composite ingots at 520 ºC. Microstructural data were assessed by the use of optical microscope (OM) equipped with quantitative data analyzer and scanning electron microscope (SEM). The results showed that hot extrusion with the ratio of 18:1 has the maximum effect on the size reduction of Mg2Si particles. Particle fracturing during hot extrusion changes the size of coarse Mg2Si particles from 92 μm to 24 μm, which shows about 75% reduction. Due to high stress–concentrated areas around Mg2Si particles, reduction in the size of primary Mg2Si particles reduces the stressconcentrated areas and results in enhancing mechanical properties.<\div>

۵Effect of Al–15Zr master alloy on the microstructure of a 2007 aluminum alloy produced by strain–induced melt activation (SIMA) process
اطلاعات انتشار: سومین کنفرانس بین‌المللی آلومینیوم ایران IIAC2014، سال
تعداد صفحات: ۹
In current research, the influence of Al–15Zr grain refiner on the microstructural of Al–4.0Cu–1.2Pb–1.1Mg–0.8Mn Al alloy has been investigated. The optimum content of Zr to obtain fine–grained structure was found to be 0.3 wt.%. Then SIMA process was applied to the unrefined and Zr–refined alloys. A pre–strain of 30% was applied to all samples and then pre–strained samples were subjected to a various holding times (5–20 min) and temperature (600–625 °C) regimes. Microstructural study was carried out on the alloy by using an optical and scanning electron microscopy (SEM) in both unrefined and 0.3 wt.% Zr–refined samples. The results showed that to achieve desired microstructure during SIMA process, the optimum temperature and time were found to be 615°C and 10 min, respectively. The results show that by applying SIMA process at optimum conditions, the average grain size decreases to 54.7 μm and 52.9 μm in unrefined and 0.3 wt.% Zr–refined samples, respectively. The sphericity of grains also increases to 0.754 in unrefined and 0.82 in 0.3 wt.% Zr–refined specimens<\div>
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