Mechanical Behavior of Deformable Particles Reinforced Al Matrix Composites

Metal matrix composite reinforced by ceramic particles generally demonstrated a significant improvement in strength, while its ductility is suppressed sharply due to the incompatible deformation between matrix and rigid reinforcements. In this work, the SiCp/2024Al composites particles have been used as deformable reinforcement, which has lower elastic modulus and considerable elongation. Three Al alloys (1050Al, 2024Al, and 7A60Al) have been used as the matrix, respectively. Compared with the uniformly distributed SiCp/Al composites with the same SiC particle amount (30 vol%), the deformable particle/2024Al composites showed comparable tensile strength and higher toughness. In-situ strain observation, fracture surface analysis, and finite element method simulation proved the main deformation mechanism in the composite shifts with the increase of matrix strength. For low-strength matrix, strain concentration occurred in the matrix, while for high-strength matrix, reinforcements could also undergo plastic deformation. It could be inferred that uneven strain distribution and stress localization could be alleviated, even avoided for composites with designed ductile reinforcement, which are crucial factors for composites' ductility and machinability. A semi-empirical model was derived from statistics to describe the strengthening behavior of the composites reinforced by deformable particles. Further discussion revealed that the optimal value of the ratio between the yield strength (YS) of reinforcement and the matrix (sigma py/ sigma my) exists, by which the strength of the composite reaches the maximum value. Accordingly, the optimal ratio could be rationalized by experiments that uniform strain distribution was observed in the deformable particle/2024Al composites.