In order to understand effects of shot blasting treatment on surface hardness and roughness of ADC12 aluminum alloy

the surface hardness and roughness of the samples before and after shot blasting treatment on ADC12 alloy sgueezing casting samples with various processes were measured

and their appearance after shot blasting treatment was observed.The results reveal that the roughness of ADC12 alloy sgueezing casting samples after shot blasting treatment is in range of 2.850

6

.515μm

and the hardness（HV）is improved to 107

1

63from 100.In addition

the test results exhibit a certain patterns in roughness and hardness at various processes.The process of shot blasting treatment is equivalent to conduct micro forging on the surface.The constant impact of steel balls on aluminum alloy changes the original surface crystal structure of the alloy

and causes micro-convection on the surface to generate a lot of dislocation in the structure of surface crystal

which in turn harden the surface of alloy sample.The plastic deformation combined with rougher surface can increase effectively the degree of oxidation to improve the surface hardness.Surface hardness can be decreased due to generation of defects during shot blasting treatment

and with increasing in blasting velocity or blasting time

strengthening layer thickness of sample surface is increased

and it is beneficial to forming the more serious surface wave accompanied with defect formation

which is responsible for roughness increase of sample surface.