A vacuum-assisted die-casting experiments of SiC/6061 composites were carried out

and the formation mechanism of the surface layer and the internal pores of samples with different wall thicknesses

and their influence on the mechanical properties of the samples were investigated.The results show that there exists a surface layer with a thickness of about 0.5 mm in the samples with different wall thicknesses

and the 2 mm wall thickness samples are dominated by scattered gas pores.When the wall thickness is increased to 4 mm

the pores are dominated by gas-shrinkage pores.Large-sized shrinkage pores are discovered

and most of pores are concentrated in the central area of the sample axis.During the tensile test process

large shrinkage pores can induce brittle fracture of the sample

and the internal particles can cause brittle failure of the surface layer

resulting in a decrease in the tensile properties of the HPDC SiC/6061 composites.