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Titanium is an extremely ductile metal. For that reason, it is tricky to polish, grind, and cut in preparation for microscopic observation. In this guide, we hope to outline the most efficient ways of prepping pure titanium and its alloys for metallographic examination.
Microstructure and metallurgy of titanium
Metallography plays a pivotal role in titanium’s quality control. This includes everything from overseeing the initial production procedure to inspecting porosity on cast parts and managing heat treatment. Not to mention, it plays a major role in the development and research of titanium alloys and items.
At a temperature of 882ºC, titanium has an allotropic shift. It goes from a low-temperature, close-packed hexagonal structure (α) to a body-centred cubic phase (β). Such a change makes it possible to generate alloys with β or mixed α/β microstructures. This permits the use of thermo-mechanical and heat treatment. As a result, you can obtain various properties from a relatively compact number of alloy compositions.
To guarantee the right mix of properties and microstructure though, you must keep close control of the treatment process. This makes metallography vital.
However, you need to think about prep when you are taking samples. There are a number of things to keep in mind here. Then you can contact us if you need titanium grade 2 round bar, plate, and sheet items.
Cutting
Thanks to the high ductility, cutting or machining tends to generate long chips. Due to this, cutting with standard aluminium oxide cut-off wheels is ineffective. It often results in heat damage. The solution here is using silicon carbide cut-off wheels. They have been specifically developed to section titanium.
Mounting
In primary production control labs, large titanium samples are usually processed unmounted. But, smaller parts always need to be. What this does is simplify the preparation. It will also ensure that you receive the best results in relation to reproducibility and accuracy. For that, it is a good idea to use cold mounting with slow-curing epoxy or phenolic resin.
Polishing and grinding
Thanks to the extreme ductility, titanium is vulnerable to mechanical scratching and deformation. This is during metallographic preparation. You should avoid diamond polishing, particularly with commercially pure titanium. It can cause deformation on the exterior in the form of smearing and scratching. That can be hard to remove. Instead, it is preferable to use a chemical mechanical polish to avoid the problem.
There is a three-step method you can use here. It is an automatic one that has been proven to offer excellent and reproducible results.
- With the first step, you plane grind with resin-bonded diamonds in a rigid disc.
- For step two, you perform fine grinding on a hard exterior using an abrasive 9 µm diamond suspension.
- As for the final step, this would be chemical-mechanical polishing with a mix of hydrogen peroxide and colloidal silica.
Preparation time here will rely on the titanium and sample area. The purer your metal and larger your sample, the longer the final polishing step is going to take.
Carry on polishing until your exterior appears white in an optical microscope. Titanium and its alloys should typically appear extremely clean after you polish. This means that any compact black dots you see are most often because of grinding deformation. You need to remove them with chemical-mechanical polishing.
After the polishing you should be able to see the structure in polarised light without etching. It will ensure you can confirm the quality of the titanium.
Come to us for stellar titanium grade 2 round bar, plate, and sheet
At Brindley Metals, we provide first rate products to all our customers. This is true whether you need primary materials like bars, plates, and sheets or final parts like rings. Also, we have a rapid delivery service that we use to ensure you are not waiting long for orders.
As specialists in our field, you can rely on us for all your needs. Therefore, if you need titanium grade 2 round bar, plate, and sheet, make sure you come to us. Get in touch for any info on grades and more.