Microstructure and property evolution during solution and aging treatments of an Al-8.9Zn-2.0Mg-1.8Cu alloy
Solution treatment enables 7xxx series alloys to achieve a supersaturated solid solution,which precipitates strengthening phases during aging,ultimately resulting in high comprehensive properties.This experiment studied the evolution of the microstructure and mechanical properties of an Al-8.9Zn-2.0Mg-1.8Cu alloy during solution and aging treatments,and based on these findings,optimized solution and aging treatment regimes were determined.The results indicated that after solution treatment at 470℃～480℃for 1 hour,the Mg(Zn,Cu,Al)2 phase in the alloy completely dissolved,with only Fe-rich phases remaining.Extending the solution treatment time at 470℃showed no significant change in the Fe-rich phases,and the tensile properties of the alloy remained essentially unchanged.The suitable solution treatment regime for the alloy was determined to be 475℃/1h.During single-stage aging,with the extension of aging time,the hardness of the alloy initially increased rapidly and then stabilized,showing an overall increasing trend.The higher the single-stage aging temperature,the faster the initial increase and the higher the values.The evolution of the alloy strength followed a similar pattern to that of hardness.With prolonged aging time,the electrical conductivity showed an increasing trend;the higher the aging temperature,the greater the electrical conductivity.During aging at 120℃,as the aging time increased,the size of the matrix precipitates in the alloy grew,and the size distribution range of the precipitates widened.The main precipitates transitioned from GPI zone,GPII zone and η'phase in the early stage to GPII zone,η'phase and η phase.The suitable peak aging regime was determined to be 120℃/48h.
7xxx aluminum alloySolution treatmentAging treatmentMicrostructure and property
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