Effects of Zn additions and aging process on microstructure and mechanical properties of 2056 aluminum alloy

The effects of Zn additions and aging process on the microstructure and mechanical properties of 2056 aluminum alloy were investigated by micro-hardness test, tensile test, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that the tensile strength (σ b) and yield strength (σ 0.2) of 2056 aluminum alloy are higher than those of the alloy without Zn while the elongation is almost the same in T6, T8 and T3 temper. This is because with the addition of Zn, Zn-rich clusters form, which accelerates the precipitation of GPB zone and the precipitation of S' phase further, thus improving the strength of the alloy. The order of σ b and σ 0.2 of 2056 aluminum alloy in T3, peak-aged T6 and T8 temper from large to small is T8, T3 and T6. The predeformation before aging makes plenty of dislocations form. Due to the strong interaction between the solute atoms and dislocations, there exists large quantity of dislocation pile-up while dislocations become tangled up, which improve the strength in T3 temper. In T8 temper, the dislocations become the precipitation sites of S' phase, making fine, dense and uniform S' phase in the matrix. The strength of the alloy in T8 temper improves a lot compared with that of T6 and T3 temper.