Comments on “cluster hardening in an aged Al-Cu-Mg alloy”
Comments on “cluster hardening in an aged Al-Cu-Mg alloy”
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DOI：
10.1016/s1359-6462(98)00365-0
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发表时间：
1998-11
影响因子：
6
通讯作者：
A. Zahra;C. Zahra;C. Alfonso;A. Charaï
中科院分区：
文献类型：
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作者：
A. Zahra;C. Zahra;C. Alfonso;A. Charaï
最近，Ringer et al. [1-3]利用原子探针场离子显微镜、高分辨电子显微镜（HREM）和微束电子衍射对Al-1.1 at% Cu-1.7 at% Mg合金中的沉淀现象进行了研究。在高于100 ℃的温度下的极快的初始硬化反应被认为是由于Cu-Mg共簇的形成。由于它占总硬化的60%左右，提出了一种新的簇硬化机制。棒状相干Guinier-Preston-Bagaryatsky（GPB）区仅在老化过程后期（150 ℃下100 h）检测到，并被认为是硬化第二阶段的来源。此外，无论老化时间（长达500小时），没有观察到S相。本文的目的是证明在低于200 ℃的所有温度下，即使在短时效时间内也会形成GPB区，以证实通常不被承认的亚稳S相的存在，并指出过去已经观察到簇硬化。我们的论点是基于以前的[4-6]和使用量热法，HREM和能量色散光谱（EDS）进行的新实验。研究了三种高纯度铝基合金：-合金A含有0.87原子% Cu和1.44原子% Mg，与Ringer等人研究的合金相当;-具有0.90原子% Cu、1.46原子% Mg和0.03原子% Zr的合金B（由于Zr-空位优先结合，Zr的添加降低了过饱和固溶体的分解速率）-具有0.85原子% Cu的合金C。
Recently, Ringer et al.[1–3] published results on precipitation phenomena in an Al-1.1 at% Cu-1.7 at% Mg alloy obtained by atom probe field ion microscopy, high-resolution electron microscopy (HREM) and microbeam electron diffraction. The extremely rapid initial hardening reaction at temperatures higher than 100 C was identified as being due to the formation of Cu-Mg co-clusters. As it amounts to some 60% of total hardening a new cluster hardening mechanism was proposed. Rod-like coherent Guinier-Preston-Bagaryatsky (GPB) zones were detected only late in the ageing process (100 h at 150 C) and considered to be the source of the second stage of hardening. In addition, whatever the ageing time (up to 500 h), no S phase was observed. The aim of this comment is to demonstrate the formation of GPB zones even for short ageing times at all temperatures below 200 C, to confirm the existence of a metastable S phase which is not generally admitted, and to point out that cluster hardening has already been observed in the past. Our arguments are based on previous [4–6] and new experiments performed using calorimetry, HREM and energy dispersive spectroscopy (EDS). Three high-purity aluminium-based alloys were investigated:—alloy A contains 0.87 at% Cu and 1.44 at% Mg and is comparable to the one studied by Ringer et al.;—alloy B with 0.90 at% Cu, 1.46 at% Mg and 0.03 at% Zr (the Zr addition lowers the decomposition rate of the supersaturated solid solution due to preferential Zr-vacancy bonding)—alloy C with 0.85 at% Cu.