Aluminum alloys are applied in many aspects of daily life, from the food industries to automobiles and aviation industries. Aluminum alloys show several properties such as high specific strength and corrosion resistivity in which have made them one of the most desired and applicable alloy systems. Although many aluminum alloys offer typically low to intermediate strength, alloys containing precipitation-hardening elements, particularly Cu (2XXX) can have proper mechanical properties similar to some hard materials.

In this work, the as-cast and thermal treated Al-Cu (Mg-Ag-TiB₂) alloys were prepared in the medium cooling rate (solidification) for the evaluation of mechanical properties (room and elevated temperature). Furthermore, for Al-Cu (Mg-Ag) class, tensile tests were carried out at the ambient and elevated temperature for all slow, medium, and fast cooling rates. Mechanical properties and deformation behavior of alloys were evaluated by tensile test results.  Alongside the fracture surface mechanisms, the microstructure of each sample was studied by scanning electron microscopy (SEM) for both as-cast and heat-treated conditions.

In general, yield and ultimate tensile strength (YS, UTS) were promoted after the heat-treatment process, while elongation to failure is reduced compared to as-cast alloys. Results at ambient testing temperature revealed that based on the solid solution and dispersoid strengthening mechanisms, the presence of alloying elements improves mechanical properties for as-cast alloys. Also, heat-treated alloys showed higher YS, UTS compared to as-cast alloys resulted in a precipitation hardening mechanism. Because of the TiB₂ component, the as-cast and heat-treated A205 alloy represented the highest mechanical properties arising from forming continuously rigid, fine, and coherent precipitate particles in the aluminum matrix. Furthermore, the influence of the artificial aging process on A205 alloy showed that over-aged alloys tested at ambient temperature had higher YS and UTS compared to as-cast and under-aged specimens. Besides, the influence of grain size on mechanical properties for Al-Cu -Mg-Ag alloy demonstrated that the rapid solidification rate (fine grain size) has been made the alloy with higher YS and UTS.

Moreover, for elevated testing temperature (250°C), based on the easier movement of dislocations, the YS and UTS decreased or remained stable. Also, the value of elongation to failure showed a significant increase compared to ambient testing temperature.

 Furthermore, SEM images illustrated that as-cast and heat-treated Al-Cu (Mg-Ag) and Al-Cu (Mg) alloys underwent a brittle deformation with intergranular and transgranular fracture mechanisms (cleavage) at ambient temperature, where at elevated testing temperature, forming of some dimples was observed (higher elongation). Besides, for as-cast and heat-treated Al-Cu and A205 alloys at ambient temperature, small dimples with higher depth were seen in which it approves ductile deformation. However, at elevated temperatures, SEM images of Al-Cu and A205 indicated deeper dimples in the as-cast fracture surface (higher elongation). Also, for heat-treated alloys at the elevated testing temperature, the fracture surface consists of shallow micro dimples. It is attributed to less elongation compared to as-cast samples.