The microstructure and mechanical properties of carbon fiber/aluminum composites fabricated by Friction Stir Processing

摘要

Carbon fiber is a low cost engineering material with superior mechanical properties, which has been used as an important reinforcement for the metal-matrix composites to improve their mechanical properties. There are two major challenges in fabricating carbon fiber reinforced aluminum composites: the uniform dispersion of carbon fiber in aluminum matrix and strong bonding at aluminum/carbon fiber interface, which are possible to be solved by direct Friction Stir Processing (FSP). In this study, carbon fiber reinforced Aluminum2024 bulk composites are fabricated by multiple-pass FSP. It is found that the carbon fiber is broken owing to the severe deformation during FSP, and the carbon fiber segments in random orientation with the length of 20 to 40μm are dispersed in the matrix homogeneously. The HREM images demonstrate that sufficient bonding is formed between carbon fiber and aluminum matrix, and no layer is found at the interface between carbon fiber and aluminum matrix. It is showed that the hardness of the composites is significantly higher than the base metal and FSPed matrix metal. The tensile test reveals that the ultimate tensile strength of the composites rise with the increasing of rotation speed. The ultimate tensile strength of the composite increases by 12.2% at the FSP parameter of 1800 rpm and 100mm/min in comparison with the base metal. The strengthening mechanisms are analyzed by using Orowan looping strengthening and load transfer strengthening.