Mechanical Property of M40J_f/5A06Al Composite at Elevated Temperatures

Abstract

In this work, aluminum alloy with a high concentration of magnesium (5A06) was reinforced with 55 vol% unidirectional ultra-high modulus and highly graphitized carbon fiber (M40J) using pressure infiltration method. The effect of temperature on the bending strength of the C_f/Al composites was investigated from room temperature to 500 °C. The experimental results showed that the strength of M40J_f/5A06Al composites was not affected by temperature from room temperature to 200 °C. The bending strength of the composite at 300 °C was decreased by 30% compared with that at room temperature. In order to evaluate the extent of interface weakening, the length of fiber pullout was measured. The results showed that the pullout length reached the maximum at 300 and 500 °C, which indicated weak interface at the corresponding temperature. The DSC curve presented obvious heat absorption peak at around 300 °C, which may be attributed to the dissolution of the interfacial product β (Al₃Mg₂) phases at the C/Al interface. The bending fracture surfaces of the composites after three-point bending tests were observed by SEM, plastic-viscous flow of the matrix were observed at the samples tested at 500 °C. The predominant mechanisms for high-temperature damage of M40J_f/5A06Al composites are matrix softening caused by dislocation recovery and interface weakening caused by the dissolution of interfacial products.