


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.





![SEM micrograph of the third specimen at 3000X 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.](https://www.researchgate.net/profile/Behzad_Nikfar/publication/235971349/figure/fig6/AS:393550115164176@1470841067937/SEM-micrograph-of-the-third-specimen-at-3000X-magnification-Because-of-high-external.png)
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