Effects of Different Ageing Processes on Microstructure and Mechanical Properties of 2023 Aluminum Alloy Containing Trace Additon of Sc and Zr

The effects of different ageing processes on microstructure and mechanical properties of 2023 aluminum alloy containing trace addition of Sc and Zr were studied by microhardness testing, tensile testing, optical microscopy and transmission electron microscopy. The results show that the hardness, tensile strength and yield strength of the 2023 alloy in T8 peak ageing state were higher than those in T6 peak ageing state by 25 HV, 37 MPa and 108 MPa, respectively, but the elongation of the alloy decreased by 67%. With the addition of Sc and Zr, fine and dispersed Al3(Sc1-xZrx)particles precipitated in the alloy, and thus to promote S′ phase precipitation with homogeneous and small grains. The Al3(Sc1-xZrx)particles could pin the dislocations and refine grains, also inhibit the recrystallization and growth of the grains, so the alloy obtained the microstructure with fairy few of recrystallization. Trace addition of Sc and Zr could accelerate the ageing responce rate of the alloy in T6 state, increase its ageing harding performance and promote the strength and plasticity of the alloy. But the effects of Sc and Zr were weakened in T8 state because a lot of dislocations were introduced in that state.