Role of retrogression and reaging in suppressing hydrogen-induced transgranular cracking in 7xxx Al alloys

IF 5.3 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Scripta Materialia Pub Date : 2024-09-19 DOI:10.1016/j.scriptamat.2024.116383

Yafei Wang , Hiroyuki Toda , Hiro Fujihara , Kazuyuki Shimizu , Kyosuke Hirayama , Akihisa Takeuchi , Masayuki Uesugi

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Abstract

Retrogression and reaging (RRA) treatment is a distinctive approach to counteract hydrogen embrittlement in 7xxx Al alloys without compromising strength. However, the mechanistic understanding of RRA has long centered around grain-boundary-related phenomena, while the roles of grain-interior microstructures in hydrogen embrittlement have remained unclear. Here, we demonstrate the beneficial effect of RRA in reducing transgranular cracks in a specially selected high-Zn alloy that exhibits fully quasi-cleavage cracking, thereby enabling the precise decoupling of grain-interior and grain-boundary mechanisms. Using synchrotron radiation 3D observations, we identify a significant delay in the initiation of transgranular cracks in RRA-treated specimens as compared to those in the peak-aged condition. Atomic-resolution electron microscopy observations confirm the grain-interior partial transformation from the coherent η’ phase to the semi-coherent η phase. It is proposed that the increased fraction of semi-coherent η/Al interfaces reduces hydrogen coverage at coherent interfaces, thereby suppressing transgranular hydrogen-induced debonding on the slip planes.

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逆变和再时效在抑制 7xxx Al 合金中氢诱导的跨晶格裂纹中的作用

退火和再时效（RRA）处理是一种独特的方法，可在不影响强度的情况下消除 7xxx Al 合金中的氢脆。然而，人们对 RRA 的机理理解长期以来一直集中在与晶界相关的现象上，而晶粒内部微结构在氢脆中的作用仍不清楚。在这里，我们展示了 RRA 在减少专门选定的高锌合金跨晶格裂纹方面的有益效果，这种合金表现出完全的准脆化裂纹，从而实现了晶粒内部和晶界机制的精确解耦。通过同步辐射三维观测，我们发现经 RRA 处理的试样与峰值时效试样相比，跨晶格裂纹的产生时间明显推迟。原子分辨率电子显微镜观察证实了晶粒内部从相干η'相向半相干η相的部分转变。据推测，半相干 η/Al 界面比例的增加降低了相干界面的氢覆盖率，从而抑制了滑移面上的跨晶粒氢致脱粘。

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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来源期刊

Scripta Materialia 工程技术-材料科学：综合

CiteScore

11.40

自引率

5.00%

发文量

581

审稿时长

34 days

期刊介绍： Scripta Materialia is a LETTERS journal of Acta Materialia, providing a forum for the rapid publication of short communications on the relationship between the structure and the properties of inorganic materials. The emphasis is on originality rather than incremental research. Short reports on the development of materials with novel or substantially improved properties are also welcomed. Emphasis is on either the functional or mechanical behavior of metals, ceramics and semiconductors at all length scales.