局部腐蚀对不同热处理状态7055铝合金拉伸性能的影响

Effects of local corrosion on tensile properties of 7055 aluminum alloys after different aging treatments

通过室温拉伸、金相显微镜、扫描电镜和透射电镜研究晶间和剥落腐蚀对T6态、RRA态和T73态7055铝合金板材拉伸性能的影响。结果表明:腐蚀后板材的强度和伸长率均降低,但伸长率的降低程度比强度的降低程度更大;剥落腐蚀后的性能降低程度大于晶间腐蚀后的;腐蚀后,RRA态板材的强度最高,T73板材的伸长率最高;剥落腐蚀后的T6态板材拉伸时发生脆性断裂;T6态板材腐蚀后拉伸性能的降低程度最大,RRA态的其次,T73态的最小;板材腐蚀后,表层产生大量腐蚀缺口和沿晶微裂纹,增大拉伸过程的裂纹源数量,降低拉伸性能;晶界上第二相粒子的尺寸、分布状态影响板材腐蚀后的损伤程度,进而影响拉伸性能的下降程度。

The effects of intergranular corrosion and exfoliation corrosion exposure on the tensile properties of T6-,RRA-and T73-treated 7055 aluminum alloy sheets were investigated by ambient tensile test,optical microscopy,scanning electron microscopy and transmission electron microscopy.The results show that the strength and elongation decrease after exfoliation corrosion,the drop percentage is significantly higher for the elongation than that for the strength.The drop percentage in the tensile properties after exfoliation corrosion is higher than that after intergranular corrosion.After corrosion,the strength is the highest for RRA-treated sheet,and the elongation is the highest for T73-treated sheet.For the T6-treated sheet subjected to exfoliation corrosion,brittle fracture occurs during tensile test.The drop percentage in the properties due to corrosion is the highest for the T6-treated sheet,intermediate for the RRA-treated sheet and the lowest for the T73-treated sheet.Many notches and intergranular microcracks are present on the surface of the sheet due to corrosion,and this increases the number of the crack sources,thus deteriorates the tensile properties.The size and distribution of the second phase at grain boundaries have influence on the degree of corrosion damage,consequently the drop percentage in the tensile properties.