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6124-金相样品制备的缺陷：划痕

2016-11-14 16:06阅读：

http://blog.sina.cn/dpool/blog/u/1732474030

金相样品制备的缺陷：划痕
------ Scratches：are grooves in the surface of a sample；也就是说，是指“机械划痕”










我们常说的样品上的划痕，即，Scratches，一般就是在说“grooves in the surface of a sample”。不过，这里有一个前提条件：未腐蚀。
砂纸造成的划痕称之为，机械划痕，就是沟槽；抛光后看不见而腐蚀后看见的划痕，称之为腐蚀划痕，未必一定是“沟槽”。机械划痕、腐蚀划痕，两者形成的机制、原理本质上是不同的；不过，一般而言，所有的划痕都是源自于“磨光”，机械划痕很简单，而腐蚀划痕的实质是，没有消除的磨砺造成的内部损伤带的“显现”。

http://www.steeldata.info/etch/demo/help/sample_preparation/scratches.html Scratches


Example: After diamond polishing, scratches from grinding still remain, Mag. 200×. Stratches are grooves in the surface of a sample, produced by points of abrasive particles.
Reference: Metalog Guide, page 64-67, Struers A/S, 2610 Rodovre, Dennmark. Note: Image and text by courtesy of Struers A/S company.

金相样品的腐蚀划痕，一般，也是源自砂纸，也就是磨光环节，主要原因是最后一道砂纸未能完成必要的任务，或者，之前的每一道砂纸也出现了“怠工”。结果造成抛光费时不讨好，总是抛不掉较深的沟槽或者内部损伤层。

实际上，最好每一道砂纸完成后都应当仔细检查，如果，仍存在上一步骤残留的划痕，则必须采取措施，比如制备时间延长 25% 到 50%。

当然，大家提及划痕，实际上的含义是“狭义”的，就是“机械划痕”。不过，腐蚀以后在提及“划痕”最好是带有修饰定语，机械划痕，或者腐蚀划痕。



参考资料：
[1] http://www.struers.com/Knowledge/Grinding-and-polishing Scratches - troubleshooting
Scratches are grooves in the surface of a sample, produced by the points of abrasive particles.
Make sure that after PG the surface of all samples in the specimen holder shows the same uniform scratch-pattern over the whole surface.
Repeat PG if necessary.
To avoid contamination of the grinding/polishing surface through large abrasive particles from a previous step, clean the samples and sample holder carefully after every step.
If there are still scratches left over from the previous step after finishing the current step, increase the preparation time by 25% to 50% as a first measure. If that does not help, use the expert system.
Look at the examples and expert system as follows:

6124-金相样品制备的缺陷：划痕
After FG, scratches from PG are still visible. Mag: 200×
FG 之后，PG 中存在的刮痕仍然可见。放大：200×

6124-金相样品制备的缺陷：划痕
After diamond polishing, scratches from FG still remain. The very deep vertical scratch might even be left over from PG. Mag: 200×
金刚砂抛光之后，FG 中的刮痕仍然存在。PG 之后甚至可能残存非常深的垂直刮痕。放大：200×

刮痕- 故障排除
刮痕是指样品表面由磨料颗点引起的凹槽。
确保在 PG 之后，试样夹具座中的所有样品在整个表面上具有相同且统一的刮痕图案。
根据需要重复 PG。
为避免上一步骤中的大磨料颗粒污染研磨/抛光表面，请在每一步骤之后仔细地清洁样品和样品架。
如果当前步骤完成之后，仍存在上一步骤残留的刮痕，则首要措施是将制备时间延长 25% 到 50%。如果问题仍然存在，则使用专家系统。
查看以下示例和专家系统：

Plane Grinding, PG
This is normally the first step in the grinding process. Plane grinding ensures that the surfaces of all specimens are similar, despite their initial condition and their previous treatment. In addition, when processing several specimens in a holder, care must be taken to make sure they are all at the same level, or 'plane,' before progressing to the next step, fine grinding. To obtain a high, consistent material removal rate, short grinding times and maximum flatness, totally fixed grains with a relatively large grain size are preferred for plane grinding. Suitable PG surfaces will provide perfectly plane specimens, thus reducing the preparation time on the following fine grinding step. In addition, some surfaces can provide good edge retention. During wear, new abrasive grains are revealed, thus ensuring a consistent material removal.
Fine Grinding, FG
Fine grinding produces a surface with little deformation that can easily be removed during polishing. Because of the drawbacks with grinding papers, alternative fine grinding composite surfaces are available, in order to improve and facilitate fine grinding, A high material removal rate is obtained by using grain sizes of 15, 9.0 and 6.0 µm. This is done on hard composite disks（rigid disks）with a surface of a special composite material. Thus, the diamond grains, which are continuously supplied, are allowed to embed the surface and provide a fine grinding action. With these disks, a very plane specimen surface is obtained. The use of a diamond abrasive on the fine grinding disks guarantees a uniform removal of material from hard, as well as soft, phases. There is no smearing of soft phases or chipping of brittle phases, and the specimens will maintain a perfect planeness. Subsequent polishing steps can be carried out in a very short time.
平面研磨 （PG）
这通常是研磨过程的第一步。无论样品的初始状况如何以及之前经过何种处理，平面研磨可确保所有样品表面都保持相似程度。此外，当加工同一样品夹中的几个样品时，须格外注意，在开始下一步，即精细研磨之前，必须确保这几个样品处于同一水平或“平面”上。对于平面研磨而言，为获得较高的统一材料去除率、缩减研磨时间和获得最大的平直度，最好选用尺寸相对较大的完全固定的颗粒。适当的 PG 表面可提供完美平直度的样品，进而缩减后续精细研磨步骤花费的制备时间。此外，有些表面可保留良好的边缘。在研磨期间，将释放新的研磨颗粒，以确保一致的材料去除率。
精细研磨 （FG）
精细研磨可提供变形度较小的表面，并且可在抛光期间轻松去除由此产生的变形。由于研磨纸存在缺陷，提供了替代的精细研磨复合表面，以便改进并且促进精细研磨。通过使用 15、9 和 6 µm 大小的颗粒来实现高材料去除率。这适用于配有由特殊复合材料所制成表面的硬复合研磨盘（刚性研磨盘）。这有助于不断供应的金刚砂嵌入表面中，进而完成精细研磨操作。使用这些研磨盘，可获得平直度非常卓越的样品表面。在精细研磨盘上使用金刚石研磨剂可确保硬相位以及软相位的材料去除率保持一致。不仅软相位不会出现拖尾现象，脆性相位不会出现碎屑，并且样品可保持最佳的平直度。可以在极短的时间内完成后续的抛光步骤。

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