Effect of Cu content on quenching sensitivity of Al-Cu-Li alloy
The effects of Cu content(3.15%,3.63%and 3.88%)on the quenching sensitivity of Al-Cu-Li alloy were studied by means of strength test,continuous cooling transformation and time-temperature-transformation curves calculation and microstructure characterization methods such as X-ray diffraction,scanning electron microscopy and transmission electron microscopy.Combined with theoretical analysis,the mechanism of Cu content affecting quenching sensitivity was analyzed from the perspective of precipitation driving force and nucleation site.The results show that,with the increase of Cu content,the lattice distortion energy increases,the solubility of Li decreases,the dislocations and residual second phases in the quenched alloy increase,the driving force of precipitation and sites of heterogeneous nucleation of Li-containing phase increase,and the quenching-induced phase increases.When the critical cooling rate increases,the incubation period of nose tip temperature is shortened,the strength residual rate decreases,and the quenching sensitivity of Al-Cu-Li alloy increases.The strength of T8 alloy is affected by Cu content and quenching rate.It is mainly affected by Cu content when the quenching rate is high,and the influence of Cu content decreases when the quenching rate is low.
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