应力控制下7075-T651铝合金的疲劳断裂行为

发布时间：2018-07-04 10:40

  本文选题：-T铝合金 + 显微组织　； 参考：《机械工程材料》2017年07期

【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。
[Abstract]:The fatigue tests of 7075-T651 aluminum alloy under stress control were carried out under different stress ranges (60% 蟽 _ S _ S _ (70%) 蟽 _ S _ S _ (80%) 蟽 _ s _ (90)% 蟽 _ S, 蟽 _ s as experimental alloy yield strength). The cyclic strain response of 7075-T651 aluminum alloy was studied, and the fatigue fracture morphology, surface damage morphology and microstructure were observed. The mechanism of fatigue crack initiation and propagation is analyzed. The results show that micrometer Al _ 7Cu _ 2FE particles, nanoscale 畏'(MgZn _ 2) and larger 畏 (MgZn _ 2) phases are precipitated in the test alloy, and there is a small globular GP region with the size of 3~10nm, which is controlled by a higher stress amplitude (80% 蟽 s ~ (90%) 蟽 ~ (2). The test alloy shows the fatigue behavior of softening and hardening before fracture, while at the lower stress amplitude (60% 蟽 / s, 70% 蟽 / s), the alloy softens and harms obviously and tends to stabilize, and the microporous aggregate dimple fracture occurs in the test alloy, and the fracture occurs at a higher stress amplitude. The crack source is located at the coarse inclusions Al _ 7Cu _ 2FE and the second phase MgZn _ 2, and there are a lot of dislocation entanglement. At the low stress amplitude, the crack source is located at the point where the matrix is slightly torn, and the dislocation morphology is a short or long straight dislocation line.
【作者单位】： 合肥工业大学材料科学与工程学院;合肥工业大学安徽省有色金属材料与加工工程实验室;
【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)
【分类号】：TG146.21
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本文编号：2095805