Solidification and interfacial structure of in situ Al-4.5Cu/TiB2 composite

In situ particle reinforced Al-4.5Cu/TiB2 composite was fabricated with TiO2, H3BO3, Na3AlF6 powders and Al-4.5Cu alloy by reaction in melt. The composite can be directly casted into moulds to make composite parts. TiB2 particles distribute uniformly in the matrix. The average size of TiB2 particles is 0.93 μm. At the atomic scale, TiB2 is hexagonal, and exhibits hexagon or quadrilateral shape. The orientation relationships exist in the interfaces between TiB2 particle and α-Al, and between the reinforced small Al2Cu phase and α-Al in the composite. They are $$egin{gathered} left[ {0ar 332} ight]_{TiB_2} //left[ {110} ight]_{alpha - AI} leftlangle {01ar 11} ight angle _{TiB_2} //leftlangle {002} ight angle _{alpha - AI} andleft[ {ar 1ar 32} ight]_{alpha - AI} //left[ {123} ight]_{AI_2 Cu} , hfill \ leftlangle {211} ight angle _{alpha - AI} //leftlangle {111} ight angle _{AI_2 Cu} hfill \ end{gathered}$$ . TiB2 particle is nucleation site for α-Al matrix growth in the composite. The interface between TiB2 particles and the matrix is clean and well bonded. No reaction product has been found through HREM observation. This is beneficial to the strength of the composite. The as-cast Al-4.5Cu/TiB2 composite exhibits mechanical excellent properties: the tensile strength is 416.7 MPa, the yield strength is 316.9 MPa, and the elongation is 3.3 pct.