Superbainite

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

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’.

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Audi’s audacious aluminium advertising artifice

Audi’s advert for their A6 is really beautifully made…

Suppose you could make metal do anything you wanted,
use it in ways no one thought possible,
at Audi that’s what we do,
the new Audi A6 with Aluminium-hybrid body,
engineered for a lighter touch.

The way the metal forming is done in the advert is really nice, just shaping the parts by hand, just like the clay model can be formed when producing models of the car.

The technology is interesting, and challenging, a combination of aluminium and steel parts are used to make the car body. About 20% of aluminium by weight of the car body is aluminium, that means about 40% by volume. Non-load bearing parts such as body panels are aluminium (which benefit from good stiffness/weight ratio). All of the car body is made from cold formed and warm formed steels as in conventional car body. Interesting, aluminium sections seem to be present as side impact bars and bumper. From the advert you might be left with the impression that the whole body is aluminium, or that this is something that would be desirable, especially confusing since ‘hybrid’ is also now commonly used to refer to automobiles which use combinations of different power sources for the engine.

This video shows which parts of the car body are aluminium and steel.

However these cars overall are not much lighter due to the use of aluminium. From the previous model of A6 the weight saving is 30 kg, the weight if the total car is 1575 kg unladen or 2,155 kg gross weight (figures for 4 door 2.0 diesel). I want to look up the weight of Audio A6 since they are first introduced, that’s because in all cars there has been a trends towards increasing weight, despite all the advances in decreasing the weight of the car body.

Japanese Swords are medieval nanotechnology

During Japanese sword making the steel is folded repeatedly. Each time the steel is folded the structure is refined.

The folding is a key process in sword making. Folding and striking the metal forges the surfaces back together. This process of folding, then forge welding, can be repeated as many as 16 times. The process removes impurities and helps even out the carbon content, and controls the scale of chemical segregation, and it is this which results in alternating layers of hard and ductile material.

So how can folding the steel result in a nanoscale structure?

When the steel is folded the number of layers obviously increases geometrically. 1 fold result in 2 layers, 2 folds results in 22 = 4 layers, 3 folds results in 23 = 8 layers. By the time we get to 15 or 16 layers we have 32768 layers or 65536 layers. After that the sword is forged out to have a width of around half a centimetre.

5 mm divided by 65536 = 76 nm.
(5e-3/65536=7.629e-8)

So each layer is 76 nm. So we can legitimately argue that Japanese Swords are bulk nano materials, with structure controlled on the ‘nano’ level, for metallurgists this is just routine stuff.

Edo period Forge Scene

Edo period Forge Scene

Of course Japanese swords are not true examples of nanotechnology, despite the validity of the maths the folding doesn’t really result in a controlled structure on the nanoscale due to the changes that occur during the welding process… I plan to talk more about that in a later post.

As you can see below, the laminations are typically visible on the millimetre scale.

Lamination on Japanese Sword

Lamination on Japanese Sword

Steel Poll 2

To maximise clear up any confusion I bring you the second poll. Please justify your selection in the comments section.

Second Steel Poll

Second Steel Pole
North Korean Flag Pole

Latex Poster/ Modelling Thermal Conductivity

Norman Gray and Graeme Stewart at Glasgow have provided useful examples to make posters using Latex.

I used these to make a tex file, which produced a poster using pdflatex. Should also be possible using latex command if you include graphics as eps rather than pdf. Make sure if you convert graphics to pdf or ps that you have a bounding box (use pstoeps command for example), otherwise your poster will break horribly. It was important to convert from eps to pdf using the epstopdf command rather that ps2pdf.

This saved me time by allowing me to use the equations from latex directly, and allowed me to include my graphs at high resolution – it doesn’t make sense to convert to jpg or other bit map to include in a powerpoint presentation file.

You can find the poster here: Poster (best viewed with xpdf)
and the latex file to make it here: Poster source file

Thanks to the people who showed an interest in the poster. I wish I had taken picture at the conference to make this post more dynamic!

You can also see this poster on my website http://mathewpeet.org/publications/posters/

Steel Mind Map

Mind Mapping is a method for arranging your thoughts, taking notes, and brain storming. Freemind is a java software for making mind maps. Steel is a material of major importance to society.

Steel Mind Map

My Steel Mind Map can be downloaded from http://mathewpeet.org/mind_map/Steel.mm

Recent Podcasts

Recent Pt-podcasts.

Podcast: Texture Review

Podcast: Fine Grained

Podcast: Low Carbon Superbainite

Podcast: Silicon in cementite

Podcast: Modelling

Podcast: Synchrotron

Podcast: Residual Stress

If you have software for listening to podcasts you can point it at the RSS feed for the site or for categories Podcasts or pt-podcasts.

Hmm i’m not sure that is the best way to do things and Podcasts or pt-podcasts doesn’t produce RSS feeds.

Advice appreciated, otherwise I just have to host these feeds at mathewpeet.org and edit them manually, or write something to make the feeds for me :). I’m at a bit of a loss what people want, since I don’t use any software for listening to podcasts.