Interface design and engineering in Al matrix composite with low CTE and high strength reinforced by barium strontium titanate particles

Al matrix composites with both low coefficient of thermal expansion (CTE) and excellent mechanical property has important application value in the fields of aerocraft, precise instruments. However, obtaining both low CTE and high strength simultaneously is still a challenge. In this work, huge negative thermal expansion effect derived from ferroelectric-paraelectric phase transformation of barium strontium titanate (BST) ceramic is designed and utilized in Al matrix. Low CTE is obtained in BST/Al composite at the condition of a low volume fraction of BST particles. Annealing treatment is carried out to improve the interface bonding and to reduce residual stress, therefore the negative thermal expansion effect in the process of phase transformation of the BST particles is more thoroughly brought into play, and then the CTE of BST/Al composite is further decreased. Finally, the average CTE of BST/Al composite annealed at 600 degrees C for 2 h between room temperature and 250 degrees C reaches as low as 12.04 x 10(-6) degrees C-1, while achieving a high compressive strength as high as 800 MPa. The microstructure around the interface and the phase transformation behavior are also investigated.