双级时效对7XXX系铝合金力学性能及晶间腐蚀性能的影响

Influence of two-step aging on mechanical properties and intergranular corrosion performance of 7XXX aluminum alloy

采用常温拉伸、电导率、硬度、金相显微镜、扫描电镜及晶间腐蚀实验,研究了二级时效时间对7XXX系铝合金力学性能和微观性能的影响。结果表明,7XXX系铝合金经双级固溶、二级时效处理后,屈服强度、硬度及电导率随时效时间的增加而增大,抗拉强度变化不明显,断裂伸长率随时效时间的延长不断下降;二级时效165℃、16 h后屈服强度、硬度、电导率、抗拉强度、断裂伸长率分别为661 MPa、70 HRB、34.68%IACS、684 MPa和13.67%;金相照片显示合金内部存在未溶第二相及杂质相,经EDS能谱分析显示为Al7Cu2Fe相和含Si杂质相;二级时效165℃、16 h后,晶间腐蚀深度达到最小值23.34μm,耐晶间腐蚀等级由3级提高至2级。

The influences of the two-step aging time on mechanical properties and microstructure of 7XXX aluminum alloy were studied by the experiments of normal temperature tensile,electrical conductivity,optical microscopy（ OM）,scanning electron microscopy（ SEM）and inter-granular corrosion. The results show that after the two-step solid solution and two-step aging on 7XXX aluminum,its yield strength,hardness and electrical conductivity increase with the increase of aging time,and the tensile strength changes little while the rupture extension decreases with the increase of aging time. The yield strength,hardness,electrical conductivity,tensile strength,and rupture extension reach 661 MPa,70 HRB,34. 68% IACS,684 MPa,13. 67% respectively when two-step aging is at 165 ℃ for 16 h.The undissolved second phases and impurity phase are found in alloy by metallograph,which are confirmed as Al7Cu2 Fe and impurity phase containing Si by EDS. The intergranular corrosion depth reaches the maximum 23. 34 μm,and the grade of intergranular corrosion resistance improves from the third grade to the second grade after two-step aging at 165 ℃ for 16 h.