应力控制下7075-T651铝合金的疲劳断裂行为  

Fatigue Fracture Behavior of 7075-T651 Aluminum Alloy under Stress Control

作　　者：陈涛[1] 赵路远 李慧[1] 黄俊[1,2] 吴玉程[1,2] 

机构地区：[1]合肥工业大学材料科学与工程学院,合肥230009 [2]合肥工业大学安徽省有色金属材料与加工工程实验室,合肥230009

出　　处：《机械工程材料》2017年第7期1-5,12,共6页Materials For Mechanical Engineering

基　　金：国家自然科学基金资助项目(51201054);国家51批博士后面上基金资助项目(2012M511400);教育部博士点基金资助项目(20120111120030);安徽省科技攻关计划项目(1301021006)

摘　　要：在不同应力幅下(60%σ_s,70%σ_s,80%σ_s,90%σ_s,σ_s为试验合金屈服强度)对7075-T651铝合金进行了应力控制下的疲劳试验,研究了其循环应变响应,观察了疲劳断口形貌、表面损伤形貌以及显微组织,分析了疲劳裂纹的萌生及扩展机制。结果表明:试验合金中析出了微米级的Al7Cu2Fe颗粒、纳米级的η′(MgZn2)相和尺寸较大的η(MgZn2)相,此外,还存在尺寸为3~10nm的细小球状GP区;在较高应力幅(80%σ_s,90%σ_s)控制下,试验合金表现出先软化后硬化直至断裂的疲劳行为,而在较低应力幅(60%σ_s,70%σ_s)下则先软化后明显硬化并趋于稳定;试验合金主要发生微孔聚集韧窝型断裂,在较高应力幅下,裂纹源位于粗大夹杂物Al7Cu2Fe和第二相MgZn2处,位错大量缠结,而在低应力幅下,裂纹源位于基体轻微撕裂处,位错形态为分散的短或长直位错线。Stress controlled fatigue tests at different stress amplitudes,60%,70%,80% and 90% of yield strength（σs）of the tested alloy,respectively,were conducted on 7075-T651 aluminum alloy.The cyclic strain response of the alloy was studied,the fatigue fracture morphology,surface damage morphology and microstructure were observed and the initiation and propagation mechanisms of fatigue crack were analyzed.The results show that micro-scale Al7Cu2 Fe particles,nano-scaleη′（MgZn2）phase and relatively large sizedη（MgZn2）phase were precipitated in the tested alloy.Moreover,fine and sphere-like GP zones with size of 3-10 nm were observed.Under the control of relatively high stress amplitude（80%σs,90%σs）,the tested alloy showed a fatigue behavior of first softening then hardening until fracture,while first softening then hardening until becoming stable relatively at low stress amplitudes（60%σs,70%σs）.The tested alloy mainly fractured in a micropore gathered dimple manner.At high stress amplitude,fatigue cracks initiated at the coarse inclusion of Al7Cu2 Fe and second phase of MgZn2,with dislocation tangling a lot.Whereas at low stress amplitude,the crack source was at the slightly torn position of the substrate,and the produced dislocation showed shapes of dispersed short or long straight dislocation lines.

关 键 词：7075-T651铝合金 显微组织 疲劳断裂行为 

分 类 号：TG13[一般工业技术—材料科学与工程]