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

In situ particle reinforced Al-4.5Cu/TiB2 composite was fabricated with TiO 2, H3BO3, Na3AlF6 powders and Al-4.5Cu alloy by reaction in melt. The compo site can be directly casted into moulds to make composite parts. TiB2 parti cles distribute uniformly in the matrix. The average size of TiB2 particles is 0.93 mum. At the atomic scale, TiB2 is hexagonal, and exhibits hexagon or quadrilateral shape. The orientation relationships exist in the interfac es between TiB2 particle and alpha -Al, and between the reinforced small Al 2Cu phase and alpha -Al in the composite. They are [0-332](T)iB // [110](<) alpha>-Al, (01-11)(T)iB // (002)(<)alpha>-Al and [-1-32](<)alpha>-Al // [12 3](A)lCu, (211)(<)alpha>-Al // (111)(A)lCu. TiB2 particle is nucleation sit e for alpha -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 exce llent properties: the tensile strength is 416.7 MPa, the yield strength is 316.9 MPa, and the elongation is 3.3 pct.