The effects of different cryogenic holding times（12、24、36、48 h）were mainly investigated on the residual stress

density

microstructure and mechanical properties of 3D orthorhombic C

f

/Al composites with a fiber volume fraction of 50% prepared by vacuum infiltration

and the influence mechanism was analyzed.The results indicate that cryogenic treatment can improve the microstructure and density of 3D orthorhombic C

f

/Al composites

which also has a significant effect on the residual stress and mechanical properties.After cryogenic treatment

the residual stress of 3D orthorhombic C

f

/Al composites is decreased

and it is decreased continuously with the increase of the cryogenic holding time.The cryogenic treatment can significantly enhance the tensile strength and elastic modulus of the 3D orthorhombic C

f

/Al composites

which can reach maximum value of 841.33 MPa and 132.19 GPa after 36 h

and increased by 13.9%、24.9%compared with those in the as-cast state

respectively.Besides

the microstructure improvement and the residual stress release are the main reasons for enhancing mechanical properties of 3D orthogonal C

f

/Al composites.