Effect of Titanium Addition and Cooling Rate on Primary α(Al) Grains and Tensile Properties of Al-Cu Alloy

The research was conducted for castings with 3-25-mm wall thicknesses and using AlTi5B1 master alloy as well as AlTi75 additions. A thermal analysis was performed to determine the real cooling rate and the degree of undercooling (ΔTα = Tα − Tmin, where Tα—the equilibrium solidification temperature, Tmin—the minimum temperature at the beginning of α(Al) solidification) of an Al-Cu alloy. It was shown that the Ti-based grain-refining process does not influence the cooling rate. Metallographic examinations were carried out to determine the primary grains (the number of primary α(Al) grains per unit volume). It was found that the grain count can be properly described by the exponential function of the undercooling for castings processed under various cooling and metallurgical conditions. Combining the cooling rate and the efficient grain refiner increased the tensile ductility by up to 150%.