SiO

2

aerogel（SA）reinforced aluminum matrix composites were prepared by casting

cold rolling and T6heat treatment.The effects of SA content on the microstructure（as-cast and cold-rolled and T6）and mechanical properties of Al-4Cu-0.1Sn alloy were investigated.The results indicate that the SA can be effectively added to the Al-4Cu-0.1Sn alloy

which is uniformly distributed into the crystal grain in form of sphere.In the as-cast state

the microhardness of the alloy shows an upward trend with the increase of SA.When the SA content is 0.02%

the average hardness reaches the highest of HV85

which is 49% higher than that of the alloy without SA

while the tensile properties of the alloy are slightly decreased with SA in the as-cast state.In the cold-rolled T6 state

when the SA content is 0.02%

the hardness of alloy is HV138.With the increase of SA

the yield strength and tensile strength of the alloy are firstly increased and then decreased.When the SA content is 0.04%

the yield strength and tensile strength of the alloy reach 320MPa and 401MPa

respectively

which is 10.3% and 10.7% higher than those of the alloy without SA.The mechanism SA enhancing the as-cast hardness of the Al-4Cu-0.1Sn alloy is to refine grains of the as-cast alloy and lead the second phase at the grain boundary to converting from a coarse skeletal shape to a fine discontinuous shape.The mechanism of adding SA to increase the strength of the T6state is to refine the Al

2

Cu phase and eliminate Al

7

Cu

2

Fe phase.