To whom it may concern:

The purpose of this memorandum is to discuss some of the sources of variation in anodizing response of aluminum plate products.  Anodizing can be influenced by local variations in composition, precipitate distribution, and grain structure that develop naturally during fabrication.

这个文件的目的是讨论铝板阳极氧化现象变化的来源。在制造过程中，阳极氧化自然会受到局部成分变化，沉淀的分布，和晶粒结构的影响。

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Aluminum wrought plate is fabricated from thick, direct chill cast ingot.  During the solidification process, solute elements (in the case of 7075, predominantly Zn, Cu, and Mg) are pushed out of the initial metal to solidify and into the remaining liquid, which results in a composition gradient through the thickness (and across the width) of the ingot.  This gradient persists through fabrication, and influences the subsequent formation of precipitates, such that the final plate will have differences in composition and precipitation throughout.

 铝锻板是直接由厚，冷硬铸块锻造的。在凝固过程中，溶质元素（在7075的情况下，主要是锌，铜，镁）从原材料金属凝固到剩余的液体，结果导致铸块合成物在厚度和宽度方向有个梯度变化和分布。这种梯度变化在制造过程中一直存在，而且影响后面形成的沉淀物，正因为如此最终凝固的板材在构造和沉淀物上都有差异。 

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Another factor is that grain structure within the plate also varies through the plate thickness and across the width.  These gradients are due in part to composition differences (in this case, the dispersoid former, Cr, is the important element) and in part due to the thermomechanical processing to which the plate is subjected during hot rolling.  As gauge decreases, temperature control is more difficult to maintain, and gradients in grain structure may become more pronounced.

另一个因素是，板材内在的晶粒结构会随着厚度和宽度发生变化。这些梯度变化由于部分构造不同而产生（在这种情况下，最先析出的元素，铬是主要的影响因素），部分原因是由于热轧过程中的热处理产生的。随着尺寸减小，温度控制更难以保持，晶粒结构的梯度变化也会更加明显。

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Finally, when aluminum plate products are quenched after solution heat treatment, the quenching medium (generally water) impinges on the metal surface, efficiently removing heat.  In the interior of the plate, heat must be transferred outward to the surface, resulting in a through thickness gradient in quench rate.  This gradient in quench rate also contributes to local variations in precipitate distribution and anodizing response.
最后，当铝板产品从固溶热处理中冷却出来，淬火介质（通常是水）喷淋在金属表面上，

有效地去除热降温。在板的内部，热量必须向外传递到表面，导致在一个通过厚度梯度的淬火速率。这个淬火速率的梯度也会影响晶体的成长、沉淀的分布和阳极氧化反应。

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Given the gradients discussed above, it is not unusual to have different parts from within the same lot respond differently to anodizing, depending on their location within the lot.

鉴于上述梯度的讨论，阳极电镀时，不同一个点有不同成分是常见的，这取决于它们在这个点所处的位置。

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Because it is a natural outcome of the manufacturing process, anodizing performance in plate is not guaranteed, although Kaiser Aluminum has done a great deal of research over the past several years in an effort to minimize through-thickness differences in anodizing behavior.  This research has culminated in the recent introduction of Kaiser Select^® 6061-T651 plate, offering improved uniformity in through-thickness anodizing response.

因为这是制造过程中的自然结果，阳极氧化板材的性能不能保证，尽管Kaiser铝业在过去几年里尽量减少厚度差异对阳极电镀反应的影响进行了大量研究。本研究最终成果在Kaiser 6061-T651板最近推出，通过不同厚度的阳极氧化反应，改进板材的均匀性。

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Brian A. Cheney

Senior Staff Product Engineer

Kaiser Aluminum – Trentwood Works