Fatigue properties of 5056 Al-Mg alloy produced by equal-channel angular pressing

Nanostructured Materials Pub Date : 1999-10-01 DOI:10.1016/S0965-9773(99)00392-X

A Vinogradov , S Nagasaki , V Patlan , K Kitagawa , M Kawazoe

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引用次数: 139

Abstract

The fatigue behaviour of the fine-grain 5056 Al-alloy processed by equal-channel angular pressing (ECAP) is explored. This material exhibits a slightly enhanced fatigue life at low stress amplitudes. However, no improvement in the fatigue limit is observed. Fatigue performance is discussed in terms of fatigue life, crack nucleation and propagation. Structural changes during fatigue are investigated by transmission electron microscopy. It is shown that the fine structure achieved during processing is unstable and tends to relax with cycling, resulting in local recovery of the pre-deformed material. Structure relaxation during fatigue is supposed to provoke notable cyclic softening which is particularly pronounced at higher applied stresses. It is found that the crack growth rate is greater in the fine-grain ECAP material than in its coarse-grain counterpart. The latter is attributed to the roughness-induced crack closure and crack deflections which is more significant in conventional alloy. The improvement of fatigue properties at low-cyclic regime is believed to be due to a higher resistance to crack nucleation in the fine-grained material having a larger yield stress value.

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等径角挤压5056 Al-Mg合金的疲劳性能

研究了细晶粒5056铝合金等径角挤压(ECAP)的疲劳行为。这种材料在低应力幅下的疲劳寿命略有提高。然而，没有观察到疲劳极限的改善。从疲劳寿命、裂纹形核和扩展等方面讨论了疲劳性能。通过透射电镜研究了疲劳过程中的结构变化。结果表明，在加工过程中获得的精细结构是不稳定的，并且随着循环趋于松弛，导致预变形材料的局部恢复。疲劳期间的结构松弛应该引起显著的循环软化，在较高的施加应力下尤其明显。结果表明，细晶ECAP材料的裂纹扩展速率大于粗晶ECAP材料。后者主要是由粗糙度引起的裂纹闭合和裂纹偏转引起的，这在常规合金中更为明显。在低循环状态下疲劳性能的改善被认为是由于具有较大屈服应力值的细晶材料具有更高的抗裂纹形核能力。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Nanostructured Materials

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