AFAK the specific heat capacity per weight of aluminium is app. double that of steel. Since the density is app. half, similar cooling curves shoud be expected if the convection is the same.
yes Per u r right, i applied lumped capacitance method for this problem and it proved sw simulation
after eliminating same values for aluminium and steel, remaining values are density and specific heat
at my simulation this variables are;
2700 kg/m^3 * 1300J/(kg.K) = 3510000
7800 kg/m^3 * 440J/(kg.K) = 3432000
owing to multiplications of these values are close to each other, cooling curves are also close too.