Effects of Ti addition on microstructure and mechanical properties of 7075 alloy

In the present research, aluminium metal matrix composites (AMMCs) with different weight percentages of TiAl3 particles were fabricated by in situ stir casting process. A heterogeneous nucleation phenomenon in the cast AMMCs was studied. Microstructural characterisation was investigated by optical microscopy, X-ray diffraction and scanning electron microscopy. Tensile test was carried out in order to identify the mechanical properties of composites after aging. The primary aluminium phase which nucleated heterogeneously on TiAl3 particles has been identified with a small lattice disregistry while their crystallographic orientation relationship was (001)(TiAl3) // (100)(Al). The microstructure analysis revealed uniform distribution of reinforcements, grain refinement and clean TiAl3/Al interface in specimens. The mechanical results showed that the addition of up to 1 wt%-Ti led to an improvement in the tensile strength and ductility as compared against matrix. Fractography of the specimens showed that the fracture surfaces of as cast composite exhibited mixed rupture characteristics of quasi-cleavage and tough.