Aluminium (Al) alloys are employed, from aerospace, automotive body panel, building industry to kitchen wares. This paper attempts to close an existing gap in the usage and variation in the percentage weight (% w.t.) of two constituents [Magnesium (Mg) and Copper (Cu)] in Al alloy and evaluate the impact of such variations on yield strength in N/mm 2 and percentage elongation (% e) at ambient temperature. Experimental X7475 alloy was prepared from constituents drawn from 6 % Zn, 2.5 % -3.5 % Mg, 1.8 % -3.0 % Cu, 0.03 % Mn, 0.23 % Cr and Al as balance in all cases. The result revealed that yield strength increased with increase in Mg and decreased with increase in Cu as a maximum yield strength of 384.57 N/mm 2 was displayed by an alloy of 2.5 % Mg, 3.0 % Cu while the least yield strength of 130.00 N/mm 2 was recorded by an alloy of 3.5 % Mg, 3.0 % Cu. Ductility (% e) increased with increase in Cu. The paper submitted that mechanical properties of Al alloys depend not only on the content of alloying elements, but also on their relative chemistries with each other, impact of impurities and heat treatments.