ETCHING AGENT 2

[mechnano]

May i know for the best etching agaent to study the microstructure of alumina preform and magnesium metal matrix composite in which alumina preform as reinforcement.

thanks

 

[EdStainless]

What are you trying to see? What can you see unetched?
Have you tried polarized and DIC?

Mg is easy to etch. Dilute citric, tartaric and oxalic acids are all used.

I would consider heat tinting first though. Etching may cause too much attack and be hard to control on such a reactive metal.

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[TVP]

I agree with EdStainless-- start by observing the polished cross-section with no etching. Use polarization and DIC, as this is very effective for Mg. Heat tinting with fairly low temperatures can also be used. You should only use an acid-based etchant if you want to reveal the microstructure (grain size, grain boundary constituents, second phases, etc.) of the Mg. Is it pure Mg or an alloy? Other suitable etchants involve picric acid or even the standard 2% nital used for examining steel.