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توليد نانوکامپوزيت آلومينيوم تيتانيوم روش پرس داغ

- HAX - طراحی، مهندسی و ساخت خودروهای الکتريکی و قطعات وابسته

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توليد نانوکامپوزيت آلومينيوم تيتانيوم روش پرس داغ
توليد نانوکامپوزيت آلومينيوم تيتانيوم روش پرس داغ

Abstract and Figures

Aluminum reinforced with a large amount (up to about 55 vol.%) of Al3Ti particles can be fabricated from Al-20Ti elemental nanometer-sized powder mixture via in-situ two step hot press sintering (TSS). For production of intermetallic reinforced in-situ composite, TSS can provide elevated temperature to facilitate the formation of intermetallic phase in situ and hot consolidation to form a fully dense solid. The first step sintering was employed at a higher temperature to obtain an initial high density, and the second step was held at a lower temperature by isothermal sintering for more time than the first one to increase bulk density without significant grain growth. The optimum TSS regime consisted of heating at 625°C for 5 min (1st step) and 570°C for 40 min (2nd step) with applied pressure of 470 MPa, resulting in the formation of near full dense microstructure (0.97 TD) with suppressed grain growth.


لینک دانلود مقاله

 SEM picture of Al-20 wt.%Ti powder after 12 hours of MA
SEM picture of Al-20 wt.%Ti powder after 12 hours of MA
 SEM micrograph of the first specimen.
SEM micrograph of the first specimen.
 SEM micrograph of the second specimen.
SEM micrograph of the second specimen.
 SEM micrograph of the third specimen. SEM pictures of the specimens with 2000X magnification are shown in Fig. 10 and 11. In the pictures, the dark gray, light gray and white areas are related to the Al matrix, Al 3 Ti phase and remained Ti respectively. results of image analysis test on the SEM pictures are shown in Table 2.
SEM micrograph of the third specimen
 EDS test on the second specimen.
EDS test on the second specimen.
 SEM micrographs of the first specimen at 2000X magnification. Finer and homogeneously dispersed particles of Al 3 Ti, Al matrix and Ti phase is seen in the figure. But external pressure increase in the third specimen has caused abnormal grain growth in some areas. With respect to the results of Table 2, percentage of remained Ti in the specimens one to three is 3.8, 5.6 and 4.0% respectively which is about one fifth of the preliminary content and shows that more Al 3 Ti could be formed with giving more time to the specimens specially the third one which has finer and more homogeneously dispersed Ti which has more contact surface with Al matrix thus atomic exchange will be faster. Specially with respect to the lower temperature for the third specimen there is less concern about grain boundary diffusion which is the main reason of grain growth at high temperature. In the third specimen since external pressure was high, high density was gained but in some areas big porosities are seen which are of course smaller than in the first two specimens and has a reason that is well-known as Kirkendall
SEM micrographs of the first specimen at 2000X magnification.
 SEM micrograph of the third specimen at 3000X magnification. Because of high external pressure, grains are plastic deformed and in some cases are rotating [12] that this deformations cause the formation of supersaturated vacancies. Then these vacancies gradually move towards the grain boundaries during sintering and cause growing of the cavities [15] which is one of the main reasons of low micro hardness results for the third specimen. SEM micrograph of the third specimen at 3000X magnification is shown in Fig. 12. As can be seen in the picture, size of Al 3 Ti phases are less than micron but for seeing the phase clearly more magnification is required.
SEM micrograph of the third specimen at 3000X magnification.
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