Abstract: Using M40J-6K laminated punctured structure carbon fiber as reinforcement and ZL301 alloy as matrix, a laminated punctured C_f/Al composite was prepared by vacuum pressure infiltration method. The effects of single cryogenic treatment time (6, 12, 48 h) and cryogenic treatment cycles (1, 3, 9) on microstructure and tensile properties of the composites were studied, and the reasons for the improvement of tensile properties were analyzed. The results indicate that cryogenic treatment can improve the tensile properties and microstructure of the laminated punctured C_f/Al composites. Cryogenic treatment for 1 cycle can improve the tensile strength of the composites, while the impact on tensile modulus is relatively small. The maximum increase in tensile strength is achieved when the cryogenic time is 6 h, which increases from 559 MPa(without cryogenic treatment) to 664 MPa, by an increase of 18.8%. When the treatment time is further extended to 12 and 48 h, the effect is not significant. Compared with 1 cycle cryogenic treatment, cyclic cryogenic treatment can further improve the tensile strength and modulus of the laminated punctured C_f/Al composites. After 3 cycles of cryogenic treatment, the tensile strength and elastic modulus increase to 706 MPa and 138 GPa, respectively, compared to 676 MPa and 125 GPa under cryogenic treatment for 1 cycle, by an increase of 4.4% and 10.4%, respectively. When cryogenic treatment further increases to 9 cycles, the tensile strength and modulus are stabilized. The stress release and state change, increased density, preferred grain orientation, and increased matrix dislocation density after cryogenic treatment are the reasons that affect the improvement of macroscopic tensile properties of the laminated punctured C_f/Al composites.

Key words: cryogenic treatment, laminated punctured C_f/Al composites, tensile properties, microstructure characteristics