Effects of parameters of pulsed magnetic field and cooling conditions on size

morphology and distribution of primary Mg

2

Si phase in Mg

2

Si/Al composites were investigated.The results show that the primary Mg

2

Si phase shows coarsening tendecny

segregation and gradient distribution under pulsed magnetic field.In most conditions

the volume fraction of the primary Mg

2

Si phase is increased gradually from the center to the edge of the specimen

and gradient materials with continuous change of primary Mg

2

Si phase could be prepared sucessfully.With the pouring temperature of 760℃

the volume fraction of the primary Mg

2

Si phase is decreased at the edge of the sample.With the pulse voltage of 100V

the pulse frequency of 10Hz or the mold temperature of 400℃

absence of primary Mg

2

Si phase in the central region of the sample can be observed

while the primary Mg

2

Si phase is distributed mainly on the edge of specimen

so surface reinforced in-situ gradient composites can be prepared.In the range of 0

3

00V

with the increase of pulse voltage

the size of the primary Mg

2

Si phase is increased at first and then decreased

and the turn point is 200 V.When the pouring temperature is at 670

7

60℃or the mould temperature is at 200

6

00℃

with the increase of pouring temperature or the decrease of mould temperature

the size of the primary Mg

2

Si phase is decreased.