时效制度对2A97铝锂合金腐蚀行为和微观组织的影响

Effect of ageing treatment on local corrosion behavior and microstructure of 2A97 Al-Li alloy

通过拉伸性能测试、晶间腐蚀(IGC)和剥落腐蚀实验(EXCO)以及透射电镜(TEM)观察,研究时效制度对2A97铝锂合金力学性能、晶间腐蚀行为、剥落腐蚀行为和微观组织的影响。结果表明:135℃/36 h+175℃的双级时效比135℃的单级时效更有利于提高2A97铝锂合金的力学性能和耐腐蚀性能;随着175℃下的第二级时效时间延长,合金的力学性能和耐腐蚀性能显著提高;135℃/36 h+175℃/24 h双级时效时,晶内由大量的T1相和少量的δ′相组成,晶界析出物粗大、断续分布,此时合金具有最优的力学性能和抗腐蚀性能,其抗拉强度为605 MPa,伸长率7.7%,平均晶间腐蚀深度29.3μm,剥蚀等级为EB级。

2A97 Al-Li alloy solution hardened and pre-transmuted for 2.5% was monopole aged at 135 ℃ and duplex aged at 135 ℃＋175 ℃,respectively.The effect of aging treatment on tensile properties,intergranular corrosion behavior,exfoliation corrosion behavior and microstructure of 2A97 Al-Li alloy was investigated by using tensile test,intergranular corrosion and exfoliation corrosion experiments,transmission electron microscopy（TEM） observations.The results show that the duplex aging at 135 ℃/36 h＋175 ℃ can enhance the mechanical properties and corrosion resistance of 2A97 Al-Li alloy more effectively than single aging at 135℃.The mechanical properties and corrosion resistance of 2A97 Al-Li alloy increase with increasing the aging time at second-step temperature of 175 ℃.The mechanical properties and corrosion resistance of the alloy are optimal at 135 ℃/36 h＋175 ℃/24 h aging treatment in experiment.Lots of T1 precipitates and a few of δ′ precipitates appear in the matrix,the coarse and discontinuous precipitates appear on the grain boundaries.The tensile strength and elongation of alloy are 605 MPa and 7.7%,respectively.The average intergranular corrosion depth is 29.3 μm,and exfoliation corrosion level in EXCO solution is EB.