Improving the castability, mechanical properties and modifying the microstructure of the A201 alloy (Al - 4.97wt. % Cu – 0.56 wt. % Ag) were done by adding Si, Ti and B elements. The four alloys of A201 with additions of: (1) Si, (2) Ti and B, (3) Si, Ti and B, (4) non, were investigated in the as-cast, solution treated at 550°C for 20 hr and aged at 170°C up to 32 days conditions. Combination of different microscopes (HRSEM/EDS, TEM) and microhardness tests were used to investigate how the alloy properties influenced by the precipitation. Additions of Si resulted in the grain coarsening and an increase in the amount of near-grain boundary secondary phases. Additions of Ti and B resulted in the grain refinement, prevented hot tears, but caused a large amount of Al3Ti phase which makes the melt more viscose, and less fluid and castable. The mechanisms of the influence were recognized as facilitating the GP zones nucleation: Si atoms provide more probable homogeneous nucleation of the <001>α GP zones transforming to θ″ phase during aging; TiB2 particles serve as the sites for heterogeneous nucleation of <111>α GP zones which then transform to Ω phase. The precipitation sequence during aging was the following: SSSS → GP zones → θ″+ Ω → θ′ + Ω → θ′ → θ. The maximum microhardness was achieved with two kinds of semi-coherent precipitates in the structure: θ′ (Al2Cu-tetragonal) and Ω (Al2Cu-orthorhombic). Therefore, joint additions and corresponding thermal treatment can provide optimal microstructure and mechanical properties of the A201 based alloys.