In-situ （Al2O3+Al3Zr）p/A356 composites have been synthesized successfully by the direct melt reaction method in the A356-ZrOCl2 system. With the help of X-ray diffraction （XRD）

scanning electron microscope （SEM）

it is found that the formed Al3Zr and Al2O3 particles are fine and well distributed in the matrix. The distribution of in-situ particles in remelted microstructure becomes more homogeneous with the spheroidization of particles with the increase of remelting temperature

however

partial particles can be coarsened with the remelting temperature more than 850 ℃. The optimium remelting temperature is 850 ℃. Meanwhile

with the increase of remelting times

the particles become finer and finer with more homogeneous distribution

however

the volumetric fraction of the particles can be dropped as a result of excessive remelting times

so the optimized remelting times is 5. Tensile testing reveal that tensile strength of the composites is improved with increasing in remelting temperature and in remelting times

however

it is deteriorated with remelting temperature more than 850℃ and remelting times more than 5.