Distinct fatigue limit of a 6XXX series aluminum alloy in relation to crack tip strain-aging
Distinct fatigue limit of a 6XXX series aluminum alloy in relation to crack tip strain-aging
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DOI：
10.1016/j.msea.2020.139378
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发表时间：
2020-05
期刊：
影响因子：
6.4
通讯作者：
Y. Takahashi;R. Kuriki;J. Kurihara;Tomoyuki Kozawa;T. Shikama;H. Noguchi
中科院分区：
文献类型：
--
作者：
Y. Takahashi;R. Kuriki;J. Kurihara;Tomoyuki Kozawa;T. Shikama;H. Noguchi
在这项研究中，常规沉淀硬化A6061-T6合金（基础合金）和含有过量溶质镁（Mg）的改性合金相比，基础合金的高周疲劳性能进行了比较。特别注意疲劳寿命图上出现的一个明显的拐点，以及在各种测试条件下改性合金中随时间变化的强化（coaxing）效应。使用具有不同缺陷尺寸的试样的尝试成功地揭示了在基础合金中不存在的明显的膝关节归因于对小裂纹生长的阈值。无论缺陷大小如何，通过止裂实现的高Δ K值也明确证实了改性合金中的明显的共晶效应。在不同环境和温度条件下进行的对比试验进一步证实，主要由赋予改性合金的应变时效能力引起的裂纹尖端强化在室温下的环境空气中最显著地起作用。通过考虑溶质Mg和氢（H）与裂纹尖端位错的竞争相互作用，合理地解释了这一结果。
In this study, a conventional precipitation-hardened A6061-T6 alloy (base alloy) and a modified alloy containing excess solute magnesium (Mg) compared to the base alloy were compared in terms of high-cycle fatigue property. Particular attention was paid to the emergence of a distinct knee point on the fatigue life diagram together with a time-dependent strengthening (coaxing) effect in the modified alloy under various test conditions. An attempt using specimens with different defect size successfully revealed that a distinct knee, which was absent in the base alloy, was attributed to the threshold against small crack growth. The clear coaxing effect in the modified alloy was also explicitly confirmed in terms of the high ΔKvalue achieved by the arrested cracks regardless of the defect size. The comparative tests conducted under different environments and temperature conditions further confirmed that the crack tip strengthening, essentially caused by the strain-aging capability endowed to the modified alloy, operated most prominently in the ambient air at room temperature. Such results were rationally interpreted by incorporating a competitive interaction of solute Mg and hydrogen (H) with dislocations at the crack tip.