Development of Interpenetrating Phase Structure AZ91/Al2O3 Composites with High Stiffness, Superior Strength and Low Thermal Expansion Coefficient

Abstract

Mg alloys have the defects of low stiffness, low strength, and high coefficient of thermal expansion (CTE). The composites strategy and its architecture design are effective approaches to improve the comprehensive performance of materials, but the processing difficulty, especially in ceramics forming, limits the control and innovation of material architecture. Here, combined with 3D printing and squeeze infiltration technology, two precisely controllable architectures of AZ91/Al₂O₃ interpenetrating phase composites (IPC) with ceramic scaffold were prepared. The interface, properties and impact of different architecture on IPC performance were studied by experiments and finite element simulation. The metallurgical bonding of the interface was realized with the formation of MgAl₂O₄ reaction layer. The IPC with 1 mm circular hole scaffold (1C-IPC) exhibited significantly improved elastic modulus of 164 GPa, high compressive strength of 680 MPa, and good CTE of 12.91 × 10^–6 K⁻¹, which were 3.64 times, 1.98 times and 55% of the Mg matrix, respectively. Their elastic modulus, compressive strength, and CTE were superior to the vast majority of Mg alloys and Mg based composites. The reinforcement and matrix were bicontinuous and interpenetrating each other, which played a critical role in ensuring the potent strengthening effect of the Al₂O₃ reinforcement by efficient load transfer. Under the same volume fraction of reinforcements, compared to IPC with 1 mm hexagonal hole scaffold (1H-IPC), the elastic modulus and compressive strength of 1C-IPC increased by 15% and 28%, respectively, which was due to the reduced stress concentration and more uniform stress distribution of 1C-IPC. It shows great potential of architecture design in improving the performance of composites. This study provides architectural design strategy and feasible preparation method for the development of high performance materials.