Metallographic laboratories are commonly used for various materials such as steel, aluminum, copper, titanium, zinc, etc. There are certain differences in the properties and characteristics of these materials. Today, the metalworking team from the Pulse Metallography Laboratory will briefly introduce copper as an example.


1. Sampling stage.


The basic principle of sample selection is to take samples according to relevant standards or technical agreements. If there are no technical documents to refer to, then select representative parts for sampling. Pay attention to minimizing the impact on the sample during sampling to avoid overheating, deformation, and other situations. At the same time, pay attention to removing areas affected by sampling.


To be more specific, if you want to observe grain deformation and grain size, you usually take samples along the processing direction. If you want to observe the radial structure of the billet, then take a vertical sample. If analyzing defects, it is necessary to take samples at both the defect location and the normal location.


In addition, pay attention to the size of the sample, and it is generally recommended to have a cross-sectional area of 2 square centimeters to 10 square centimeters. Of course, this is when conditions permit.


2. Grinding and polishing stage.


Generally speaking, copper alloys have a much softer texture compared to iron alloys and do not require too rough polishing. Instead, it is important to avoid excessive force to avoid deformation.


Preliminary polishing is sufficient to remove sampling traces, which can be done using metallographic sandpaper or tools such as grinding discs. Then fine grind to P800 (lower)~P4000.


Conventional mechanical polishing can be used for polishing. It is recommended to choose a soft and fluffy polishing cloth. Generally, at least two polishing processes are required, with the latter using a polishing agent below 1 micron. Do not use diamond polishing fluid for the end polishing, as it is easy to embed. It is recommended to use alumina or silicon oxide polishing fluid.


3. Sample display.


There are two methods for displaying samples. One method is to directly observe with an optical microscope, which can reveal the impurity phase and the metallography of some copper alloys. Require polishing operations to be in place


The second method is to use chemical etching. It is recommended to refer to YS/T 449-2002 for selecting a suitable etching agent.


There are many types of polishing materials that can be selected based on one's own experience and industry practices. If there are technical standards, protocols, work instructions, and other reference materials available, relevant documents can be referenced for selection.


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