The influence of Ti on the microstructure and tensile properties of cast Al-4.5Cu-0.3Mg alloy

Current study was undertaken to investigate the effect of different amounts of titanium (0.001-0.5 wt%) on the microstructure, tensile properties and quality index of a high strength aluminum alloy (Al-4.5 Cu-0.3Mg). It was found that this alloy is susceptible to hot tearing and at least 0.05 wt% Ti is necessary to remove such a defect. The microstructural studies of the alloy revealed that Ti addition reduces the grain size from 190 μm to 48 μm, but adding higher Ti content (>0.05 wt% Ti) does not change the grain size considerably. Further investigations on tensile tests revealed that the addition of Ti increases ultimate tensile strength (UTS) but reduces elongation values. T6 heat treatment improved UTS, elongation and quality index values of the casting. Fracture surfaces via scanning electron microscopy (SEM) revealed ductile fracture mode in both as-cast and heat-treated conditions. At higher Ti contents, the presence of Al3Ti intermetallic on grain boundaries was found to be the favored path for crack growth.