The aim of the present research is to manipulate the amenability between composition-microstructure-property relationships in two kinds of Al-4Cu-xMg-0.3Ag alloys (where x = 0.4 and 1.4) having different Cu/Mg ratios (~9.54 and ~2.87). The effect of artificial ageing (T6) on the precipitation hardening behavior and resulting mechanical properties were also assessed and compared to two different scenarios of composition. Experimental results revealed that the modification in Magnesium concentration from 0.4 to 1.4 wt.% has a marked effect in increasing the micro hardness, ultimate tensile stress, and elongation of the alloy. Based on the microstructural analysis, the enhancement in mechanical properties was explained and addressed by considering the dual role of Mg content in the base alloy. On one hand, a large size of Mg atom produces a solid solution hardening effect, while on the other hand, a high content of Mg further promotes the formation of second phase S-type precipitate (Al2CuMg) with various mixed morphologies. This unraveling co-precipitation phases within the matrix provide an obstacle for the dislocation glide thereby increasing mechanical strength and strain hardenability.

The present study aimed to investigate the influence of magnesium (Mg) on the mechanical properties and corrosion behavior of wrought Al–4Cu–xMg–0.6Ag alloys. The results from Optical Microscope, SEM, XRD analysis, and Thermo-Calc simulation were used to identify the microstructure formed after the aging process. Testing for hardness and tensile strength was conducted, in addition to corrosion testing. It was found that Mg significantly impacts the hardness of the alloys, with a high Mg content (low Cu/Mg ratio) increasing the hardness but reducing the tensile strength and ductility. This study attributed this to the formation of the S phase, which is dependent on both the quantity in the bulk and the size of the phase. The grain size was found to be finer with a higher Mg content, since the particle size inhibits grain growth during the artificial aging process. Counterintuitively, the corrosion activity was reduced in the high-Mg-content alloy due to its large particle size and the reduced galvanic cell effect. This study highlighted the importance of considering the effects of Mg on the mechanical properties and corrosion behavior of Al–Cu–Mg–Ag alloys.