About the Author
My work currently involves developing weldable high strength bainitic steels for use as armour, before this I did various other things with steel and nickel alloys (mostly steel!). Some details of those things can be found here.
My name is Mathew Peet, I have a webpage at mathewpeet.org which has some more of my stuff.
About Bainite – potted history
Bainite is a microstructure of steel that forms at temperatures intermediate between the formation of pearlite and martensite in many steels. First discovered by Davenport and Bain who conducted a series of isothermal transformation experiments.
Historically there has been much discussion in the literature about the mechanism of transformation of bainite, with opinions varying from it being very similar to pearlite, to it being similar to martensite. Results of Ko and Cottrell showed that bainite exhibited a surface relief consistant with a martensitic transformation mechanism. Shortly after Matas and Hehemann introduced the concept of a sub-unit mechanism to explain the apparant inconsistancy between the slow speed of transformation and the high speed the interface would be expected to move.
Microstructures formed as a result of continuous cooling or by welding are often very complex and this leads to lots of scope for errors in identification of microstructures. This leads to more confusion over the appearance of the microstructure an an urge to classify constituents by appearance rather than transformation mechanism.
Generally bainitic ferrite forms austenite as plates before carbon is partitioned to the austenite. Carbide precipitation can also take place either within the ferrite or between the plates of ferrite due to supersaturation. This distinguishes upper-bainite and lower-bainite.
If transformation occurs without the formation of carbides the volume fraction of bainite forming will be limited by thermodynamics. Once the carbon in the austenite reaches a concentration were any new bainite that formed would have the same energy as the parent austenite. This is the ‘incomplete transformation’ and ‘T-zero concept’.
You can find more information on the phase transformations and complex properties group’s page about bainite.
About the blog
I thought It would be useful and fun for me to write this blog. Personally my aim is to develop better writing habits and to document some of the things I think about to render them useful. So far posts have included simple calculations, experimental results, discussion of what is happening in the world, and an attempt to model the revenue of James Bond movies using neural networks.
For the blog I would like to discuss about metallurgy and science and related topics, in the end everything depends on metallurgy so topics may become quite wide reaching at times. From time to time I may persuade other people to contribute to the blog too. Please feel welcome to the site and feel free to leave feedback on the posts, let me know what you want to read about.
This blog now has a companion blog http://troostite.wordpress.com/, who knows what will happen there.
This blog now has another sister blog http://acicularferrite.wordpress.com/, some content from the bainite blog is reblogged there. Maybe it will have it’s own content too.
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