The effects of different double ageing processes on the mechanical properties and microstructural evolution in the 1460 alloy were investigated. The corresponding microstructure and mechanical properties of the heat-treated specimens were studied by means of transmission electron microscopy, differential scanning calorimetry, hardness testing and tensile testing. The results show that the elongation of two-step aged (130 °C/84 h + 160 °C/24 h) samples can be increased to 8 % with a minor decrease in tensile strength (450 MPa). Throughout the two-step ageing process, the precipitation behaviour of the alloy exhibited the following characteristics: the δ′ phase formed at lower temperature dissolved into the matrix instead of coarsening and becoming over-aged at the beginning of the second ageing step; finely distributed θ′(Al2Cu) and δ′(Al3Li) at a steady state were obtained, resulting in a significant improvement in tensile strength; and the peak ductility occurred with the precipitation of T1(Al2CuLi) and consumption of δ′(Al3Li), as small δ′ particles caused a co-planar slip, resulting in lower ductility.
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