二级时效时间对7050铝合金组织和性能的影响

Effects of Secondary Aging Time on Microstructure and Properties of 7050 Aluminum Alloy

利用TEM、SEM、维氏硬度计、电子万能试验机、涡流导电仪和剥落腐蚀试验等手段研究了不同的二级时效时间对7050铝合金组织和性能的影响。结果表明,随着二级时效时间的增加,合金的硬度、抗拉强度均呈现单调下降的势态,且下降幅度有所增大;合金的电导率呈现单调上升的势态;从组织形貌来看,二级时效时间的增加使晶内η′相不断转化为η相,η相的数量不断增多;晶界上析出了η相,随着二级时效时间的增加,η相不断粗化,间距有所增大,PFZ宽度略微增加;从腐蚀结果来看,二级时效时间越长,合金的耐腐蚀能力越强,剥落腐蚀试验评定等级越高;综合而言,7050铝合金在经过(475±3)℃×40min的固溶处理和120℃×6h+165℃×(23~26)h的双级时效处理后获得了更优异的综合性能。

Effects of different secondary aging time on the microstructure and properties of 7050 aluminum alloy were studied by means of TEM,SEM,Vickers hardness tester,electronic universal testing machine,eddy current conductivity tester and exfoliation corrosion test.The results show that,the hardness and tensile strength of the alloy decrease monotonously with the increase of the secondary aging time,and the electrical conductivity of the alloy increases monotonously.From the view of microstructure,with the prolongation of the secondary aging time,theη′phase in the crystal is continuously transformed intoηphase,and the number ofηphase is increasing.Theηphase is precipitated at the grain boundary,it also becomes coarser continuously,the width of the precipitates and PFZ(precipitate-free zone)are increased slightly.From the corrosion results,the longer the secondary aging time is,the stronger the corrosion resistance of the alloy is,and the higher the evaluation grade of exfoliation corrosion test is.In a word,7050 aluminum alloy obtains better comprehensive properties after solution at(475±3)℃×40 min and two-step aging at 120℃×6 h+165℃×(23~26)h.