航空铝合金材料腐蚀裂纹扩展性能试验

Tests for corrosion crack propagation behavior of aeronautical aluminum alloys

腐蚀环境下的裂纹扩展性能是航空金属结构损伤容限设计的重要前提,为此,试验测定了3种航空铝合金材料(即2E12-T3、2E12-T42和7050-T7451)在2种腐蚀环境(3.5wt%NaCl溶液和油箱积水)下的裂纹扩展性能,在试验数据的基础上进行性能对比,并对试样断口进行SEM分析,研究了腐蚀和载荷联合作用对裂纹扩展的影响机理,研究结果表明:油箱积水环境对航空铝合金材料裂纹扩展的影响比3.5wt%NaCl溶液严重,铝合金2E12-T3和2E12-T42的腐蚀裂纹扩展性能优于铝合金7050-T7451,腐蚀环境下的氢脆效应和阳极溶解机制是造成腐蚀裂纹扩展加速的主要原因。

Fatigue crack propagation behavior in typical corrosion environments is the precondition of damage tolerance design for metallic structures in aircraft; therefore,in order to determine corrosion fatigue crack propagation behavior,fatigue tests were performed on three categories of aluminum alloys（ i. e.,2E12-T3,2E12-T42 and 7050-T7451） in two kinds of corrosion environments（ 3. 5wt% NaCl solution and fuel tank ponding） under constant amplitude loading. Corrosion fatigue crack propagation properties in different corrosion environments were analyzed and compared with each other,and the interaction mechanisms between corrosion and fatigue were deduced from fractographic studies by using SEM analysis. It is showed that the effect of fuel tank ponding on fatigue crack propagation behavior is more significant than that of 3. 5wt% NaCl solution,and aluminum alloys 2E12-T3 and 2E12-T42 hold superiority over aluminum alloy 7050-T7451 in corrosion fatigue crack propagation behavior. Corrosion crack propagation is enhanced due to the hydrogen embrittlement effect and anodic dissolution mechanism.