Study on aging process of new high-strength Al-Cu-Li-Mg-Ag alloy
Al-Cu-Li alloys are precipitation-strengthened aluminium alloys,which are widely used in aerospace and other fields due to their high specific strength,corrosion resistance and good fatigue resistance.The third-generation Al-Li alloys enhance the mechanical properties by increasing the Cu/Li ratio,which was contrary to the original intention of Al-Li alloys to reduce the mass,so it is a hotspot of research to made the alloys show higher properties while maintaining the Li element ratio as much as possible.In view of this,this article reduced the Cu content on the basis of the typical third-generation aluminum lithium alloy AA2195,and self-made a new Al-3.18Cu-0.89Li-0.37Mg-0.15Ag(mass fraction)alloy.The aging behavior and performance evolution of this type of alloy under different aging processes were compared through microhardness testing and tensile performance testing.The phase precipitation under different aging processes was analyzed based on transmission electron microscopy(TEM),including the composition of precipitated phases,the proportion and size changes of main strengthening phases.The results show that during single-stage aging,the increase in aging temperature makes the precipitated phase finer and more dispersed,inhibits the formation of δ'phase,increases the proportion of T1 phase and its diameter to thickness ratio,advances the time for artificial aging to reach the peak,and improves the alloy strength.Natural aging leads to an increase in T1 phase and δ'/θ'/δ'phase during subsequent artificial aging,significantly improving the diameter to thickness ratio of T1 phase and suppressing the precipitation of δ'phase and σ phase.There is no obvious precipitation zone at the grain boundary.Relative to single-stage aging,the yield strength increases by 12%,the tensile strength increases by 9%,the elongation slightly decreases,the peak hardness remains unchanged,and the overall performance of the alloy is better.
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