第二级时效工艺对7E49铝合金组织性能的影响

Effect of the secondary aging process on the properties and microstructure of 7E49 aluminum alloy

研究了第二级时效工艺对7E49铝合金硬度、导电率、拉伸性能和抗剥落腐蚀性能的影响,分析了合金时效析出相与断口形貌的演变规律。研究结果表明:随着第二级时效温度的升高或时间的延长,合金析出相以η′相和η相为主,晶内析出相尺寸增大,晶界析出相呈现断续分布,相间距增大,晶界无析出带(PFZ)变宽;合金强度降低但抗剥落腐蚀性能提高,韧性和塑性增强,断裂模式由脆性断裂演变成韧性断裂。第二级时效工艺分别为150℃(8~48)h、160℃(6~36)h和170℃(2~16)h时,合金屈服强度都在450 MPa以上,剥落腐蚀评级EA级以上,能够满足产品性能需求。

The effects of the secondary aging process on the mircohardness,conductivity,tensile properties,and exfoliation corrosion of 7E49 aluminum alloy have been studied and the precipitates evolution and fracture morphology of the aged alloys have been analyzed.The results show that with the increase of secondary aging temperature or the extension of time,the precipitates in the alloy are mainly η′and n phases.The size of the intragranular precipitated phases increases,the precipitated phases at the grain boundaries exhibit intermittent distribution,the interphase spacing increases,and the precipitated free zone(PFZ)widens.The strength of the aged alloys decreases,while the performance of anti-exfoliation corrosion improves,the toughness and plasticity increase,and the fracture mode evolves from brittle fracture to dimple type ductile fracture.When the secondary aging processes are 150℃(8-48)h,160℃(6-36)h,and 170℃(2-16)h,respectively,the yield strength is above 450 MPa,and the exfoliation corrosion rating is above EA level,which can meet the alloy product performance requirements.