• ## Bainite

It's not pearlite or martensite. A blog written by Mathew Peet.

## Bainite in Steels

Harry Bhadeshia’s book Bainite in Steels has reached it’s third edition. It’s available on pre-order at a price of 80 UKP and will be available from April. The third addition has an additional 40% more content to cover the developments of the 15 years of research since the previous edition.

This book is highly recommended for those who have an interest in the physical metallurgy of steels, alloy design, and solid-solid transformations.

http://www.oxbowbooks.com/oxbow/other-subjects/materials-science-engineering/bainite-in-steels-3rd-edition.html

Cover image for Bainite in Steels, 3rd Edition.

## Making a welded Damascus Knife

John Neeman Tools have posted a beautiful video of manufacturing a welded Damascus patterned knife.

5 layers of 3 different steels were forge-welded, folded, and forged. With each step being repeated 8 times. This produces a patterned with 320 layers. Finally twisting and forging the steel produces a more complex pattern.

Just checking the number of layers, I get their total to be different. My calculation of the number of layers is 5 × 28 = 1280, that is 4 times more than claimed (320 layers should be the result of folding 6 times (6 folds 5 × 26).

With 1280 folds, if we assume the thickness of the knife is 2 mm, that means each layer is 1.6 μm, 320 folds would be 6 μm layers. These are both lower than what can be resolved using the naked eye. It’s very close to the wavelength of visble light — if the metal were folded one more time, or the final thickness of the knife is less than 1 mm you would be there.

## Superbainite

Structure of superbainite. Inset is a same-scale image of a carbon nanotube. [1]

According to archaeologists, the Iron Age began in 1300 BC and lasted for around two millennia. Today, steels (alloys of iron and carbon) comprise 95% of global metal consumption and this trend shows no sign of declining.

Glancing at the media, however, one would be forgiven for assuming that steel is now a has-been. We are bombarded with stories of novel materials: carbon nanotubes, metallic glasses, graphene, carbon fibre, nickel superalloys. . . all of which are “stronger than steel”.

“Now we can construct space elevators!” claim the articles. “Let’s build a climbing frame to the moon! We’ll use this stuff to make everything!”

The observant among us, however, will note that most cars, trains and buildings still don’t feature superalloys, metallic glass or magic nanotubes. Neither are they invisible; nor do they fly; nor do they do any of the other things that journalists tend to ‘predict’.

Instead, steels somehow remain the best — and cheapest — materials for the job. Also, they are stronger than steel. This is because ‘steel’ is a vague construct used by sensationalists, with an unspecified strength guaranteed to be less than that of a novel material. Metallurgists rarely refer to ‘steel’, just as the Inuit have fifty words for snow, not one of which is ‘snow’.

## Naked Scientists on Super Bainite — Harry Bhadeshia Naked with Alan Bagg

Harry Bhadeshia and Alan Bagg appeared with the Naked Scientists (interviewed live on BBC Cambridgeshire) to talk about ‘Super Bainite’. and it’s potential applications for bearings A transcript of the interview can be read and the interview downloaded as an mp3. A seperate transcript is available for the part of the interview with Alan Bagg.

Later on in the program (around 45 mins–53 mins) there is an interview with Prof. Peter Brown about the use of Super Bainite as a armour. After which Harry and Alan field tweeted questions.

Photos of the BBC studio used for the interview can be seen on Harry Bhadeshia’s website.

## Surface relief at 200 Centrigrade, 392 F, gas mark 6

My paper has received page numbers and been published on paper, it also now has a page on phase transformations website.

http://www.msm.cam.ac.uk/phase-trans/2011/relief.html

This strange video appeared discussing the so-called bainite controversy.

## Shear Relief

I’m very happy that my paper was accepted for publication in Metallurgical and Materials Transactions A. It took a long time from performing the experiment to presenting the results, mainly because I needed to repeat the analysis which was something I wasn’t able to make time for until I had to submit the thesis.

Surface relief caused by shear transformation of bainite

In the paper atomic force microscopy is used to measure the shear component of extremely thin plates of bainitic ferrite in superbainite. The shear component is surprisingly large compared to the value we expected of 0.23–0.28 based on previous experiments carried out after transformation at higher temperatures (such as the results by Swallow and Bhadeshia).

It seems like the higher strain may help to explain why the bainitic ferrite plates are so thin and slender. It would now be really interesting to test if that is true or not, which is something I couldn’t really do by looking at the TEM and SEM images I have already.

More details on my web-page at Mathew Peet| Papers| Surface Relief Due to Bainite Transformation at 200°C

Article is currently available electronically by using DOI