Effect of Heat Treatment on the Microstructures and Mechanical Properties of Al–4Cu–1.5Mg Alloy

In this work, the influence of different heat treatments (HT) processes on the microstructure and mechanical properties of cast Al–4Mg–1.5 Mg alloy was investigated. To investigate the effect of HT, firstly Al–4Cu–1.5Mg samples were homogenized (solution treatment) at 500 °C/2h, water quenched at room temperature (RT) and then immediately exposed to an artificial aging process at 200 °C for various aging times of 1, 4, 8, 12, 16, 20 and 24 hours. Quantitative examinations after HT processes (solution treatment and aging) have shown that intermetallic phases (AlCu and AlCuMg) were dissolved in the α-Al matrix phase and distributed along the grain boundary. Some mechanical properties (HVσ, σ, σ, σ, E and δ) of a sufficient number of alloy samples exposed to different heat treatments were examined in detail. The data obtained show that the conditions of solution treatment and aging in some conditions show superior mechanical properties than the sample in the form as-cast. The highest microhardness value (126 HV) was obtained for the α-Al matrix phase, which was subjected to solution treatment (only homogenization). After aging for 1h at 200 °C, the peak value of microhardness was achieved as 289.5 HV for intermetallic phases. The highest tensile strength (σ) was obtained as 328 MPa for the sample which aged for 8h at 200 °C after solution treatment for 2h at 500 °C.