Effects of Ti–B and Si additions on microstructure and mechanical properties of Al–Cu–Mg based aluminum matrix composites

Abstract Ti–B and Si were added to an Al–Cu–Mg alloy to form various reinforcement phases. Various methods for characterizing reinforcement and bulk materials of the aluminum matrix composite (AMC) were investigated. A primary α-Al lamellar structure composed of α-Al and Al2CuMg (S) and Al3Zr phases was formed in Base alloy. The formation of the Al3Zr phase was suppressed and the Al3(Zr,Ti) phase and TiB2 particles were additionally observed in the Ti–B added alloy. Meanwhile, Mg2Si (β), Al2Cu (θ) and Al5Cu2Mg8Si6 (Q) phases were formed, and the Al2CuMg (S) phase disappeared in the Si added alloy. We deduced that Mg2Si (β) and Al5Cu2Mg8Si6 (Q) phases are preferentially formed over the Al2CuMg (S) phase, with the result that the total fraction of Mg in the matrix is decreased in Si added alloy. Several methods for measurement of mechanical properties in AMCs were attempted. Strength was evaluated by compression tests and tensile tests, in which was difficult because of the formation of a brittle Al3(Zr,Ti) phase in the AMCs. Micro Vickers and Brinell hardness tests were conducted to evaluate the hardness of the reinforcement and bulk material, respectively. Nanoindentation has advantages in evaluating the properties of each reinforcement phase, and RUSPec is suitable for evaluation of the bulk unit characteristics of AMCs.