The effect of Al−5Ti−1B on the microstructure, hardness and tensile properties of a new Zn rich aluminium alloy

The aim of the present study is to investigate the effect of Al−5Ti−1B grain refiner on the microstructure, hardness and tensile properties of a new Zn-rich Al−Zn−Mg−Cu alloy. The microstructural observations revealed that Ti addition refines the grain size (up to 95%) and dispersion of the second phase and subsequently forms rosette-shape grains. In addition, the grain refinement by Al3Ti particles resulted in an increase in the area fraction of the recrystallized regions as compared to unrefined specimens. After grain refinement and thermomechanical processes, the improvements of the tensile strength, yield strength and elongation values were nearly 33%, 25% and 1930% respectively, when compared to as-cast specimens. Computer simulation used to determine the strain and stress patterns showed a plastic strain gradient from the edge to the center of the hot worked specimen. The microscopic examination of the fracture surfaces showed dimple-like mechanism in deformed specimens while the presence of coarse eutectic constituent in interdendritic regions was responsible for brittle fracture in not deformed ones.