Cu含量对Al-Mg-Si-Cu合金微观组织和性能的影响

Effect of Cu content on microstructures and properties of Al-Mg-Si-Cu alloys

采用DSC热分析、硬度、电导率、拉伸和晶间腐蚀等测试及透射电镜组织观察,研究Cu含量对Al-Mg-Si-Cu合金微观组织和性能的影响。实验表明:180℃时效时,4种合金硬度上升至峰值后持续下降,且随着Cu含量增加,合金的时效硬度随之提高,硬化速率加快而软化速率降低;时效时电导率先下降至最低值后又持续上升,且Cu含量越高,电导率越低。随着Cu含量增加,T6和T4态合金的强度随之提高,晶间腐蚀抗力下降,但无Cu合金不发生晶间腐蚀;T6态合金析出相类型随Cu含量增加而变化,Cu含量较低时(0.6以下),析出β″相;而Cu含量为0.9时,析出相为β″相和Q′相共存;且随着Cu含量增加,析出相数量和体积分数增加而尺寸减小,T4态合金析出相为原子团簇。

The microstructures and properties of Al-Mg-Si-Cu alloys were investigated by differential scanning calorimetry,Vickers hardness,electrical conductivity,tensile properties test,intergranular corrosion and transmission electron microscopy.The hardness of the alloys aged at 180 ℃ increases to a peak value and decreases subsequently.The hardening rates of the alloys increase with the increase of Cu content,and the softening rate decreases due to overageing.The electrical conductivity of the alloys firstly decreases to a minimum value and increases subsequently.The electrical conductivity decreases with the increase of Cu content.With the Cu content increasing,the tensile strengths of the alloys in T6 and T4 increase,and the resistance to intergranular corrosion decreases,but the alloy without Cu does not present intergranular corrosion sensitivity.The kind of the precipitates in the T6 alloy varies with the Cu content increasing.β″ phase dominates in the alloys at the Cu content lower than 0.6,but β″ and Q′ coexist in the alloys with Cu content of 0.9.The number density and volume fraction of the precipitates increase with the increase of Cu content and the size decreases.The precipitates are solute clusters in the T4 alloy.