High frequency alternative electromagnetic field was implemented on the in-situ （Al2O3+Al3Zr）p/Al composites with 15% volume fraction and particle size of 2～3 μm at 870 ℃for 30 s

in which skin effect depth is 5.314 mm

and input current in coil is 80A

and alundum crucible is set on side of the coil with magnetic flux of 0.1T. The microstructure of water quenched （Al2O3+Al3Zr）p/Al composites was analyzed by scanning electron microscope （SEM）. The results reveal that the particle volume fraction in the center hardly changes while it is decreased by 10%with the distance from coil 5mm

and it is increased by about 20%nearby side of coil

exhibiting gradient effects to a certain

which is attributed to the electromagnetic force. The factors influencing particle evolved effects include particle volume fraction

particle diameter

melt temperature

magnetic induction flux and magnetic field time.