• ## Bainite

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

## British library Oral History Collection

Harry Bhadeshia fans shouldn’t overlook this important resource:

Harry Bhadeshia – Oral history of British science

## 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.

## Audi’s audacious aluminium advertising artifice

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.

## Only one million UK jobs rely on Physics

Incredibly only 1 million of UK (The United Kingdom of Great Britain and Northern Ireland) jobs depend on physics according to the institute of physics (IOP) IOP – One million UK jobs depend on physics. This seems an incredibly low number, they must have very stringent criteria about what counts as physics. This headline produced from a report that was conducted with auditors Deloitte (Deloitte Touche Tohmatsu Limited).

The IOP try to differentiate jobs which rely on “the physics base” or need employees with an advanced understanding of physics, and says employees in these physics-based businesses add to the UK economy is almost double that of the average UK employee. With a Gross Value Added (GVA) of £70,000 compared to the average of £36,000.

This should mean that these physicists make up 4% of UK employees, and their added value is (70,000-36,000)*1 million = 34,000 million or 34 trillion pounds or 0.034 trillion pounds. This compares to GDP of \$2.480 trillion \$2480 trillion (2011 – wikipedia) 2.4 trillion (2012 – google world development indicators).

Article updated on 27 Oct 2012

## 100 percent alloy

Great pedantic comment on the Amazon website.

100% alloy rant.

Component was made of “100% aluminium alloy”. If people don’t know what alloy means, why are they so keen to claim they are using it? Just because they think ‘alloy’ means it is good.

## Fictional Materials: Transparant Aluminium

Transparent aluminium is used in ‘the Star Trek Universe’ to make exterior windows of star ships. This material features strongly in the plot of the movie Star Trek IV: The Voyage Home. The crew of the enterprise has gone back in time to bring back a pair of whales to communicate with an alien probe. Once they have travelled to the past set about building a giant aquarium, but not having any earth money with which to buy the materials needed. In the end the aquarium isn’t made from transparent aluminium but from a giant sheet of perspex they get by trading the recipe for the transparent aluminium.

Despite mention of transparent aluminium, this aquarium built inside a Klingon starship actually used perspex in its construction.

Fairly realistic claims have been made about the mechanical properties of transparent aluminium, it claimed to be as clear as glass, and have the strength and density of high-grade aluminium. Star Trek science consultant André Bormanis has reasoned that the transparent aluminium is unlikely to be a conductor of electricity, presumably because it lacks free electrons that would usually give a metal it’s metallic appearance. If that is the case then this material is mis-named.

Transparent aluminium seems to be a popular meme. Aluminium Oxynitride is a polycrystalline ceramic with spinel structure which is said to have similar mechanical properties to transparent aluminium (made from aluminium, oxygen and nitrogen and processed by powder technique), which is used for high temperature viewing windows and for armour. In 2009 scientists from Oxford lead an experiment at the DESY facility in Hamburg Nagler et al. (“Turning solid aluminium transparent by intense soft X-ray photoionization”, Nature Physics 5, 693–696, 2009), in which aluminium was rendered transparent for short periods of time by bombardment with a very strong light source, which allowed exotic states of matter to be investigated. More recently Röhlsberger et al. (“Electromagnetically induced transparency with resonant nuclei in a cavity”, Nature, 482, 199–203, 2012),  have reported a similar phenomena for small clusters of atoms where the optical properties of or interest.

## Tin Pest Observation

The transformation of tin from it’s metallic state into a powdered state is increasing important due to the use of lead-free solders, which are almost pure tin.

The transformation involves two naturally occurring forms (allotropes) of tin, the semi-conducting powder form is labeled the alpha-tin and the metallic form is a beta-tin. The transformation usually occurs at low temperatures, it’s auto-catalytic, and has been observed in church organs in cold northern European countries and the buttons of Napoleon’s army when invading Russia. The auto-catalytic nature of the transformation lead to the name ‘tin pest’ because the reaction looks to eat into the metal.

The reaction can usually take several months but Davide Di Maio and Chris Hunt at the National Physics Laboratory, accelerated the transformation by seeding the tin with a cadmium-telluride powder. Cadmium-telluride has the same (diamond cubic) crystal structure as the powdered form and can therefore act to nucleate alpha-tin from the (tetragonal structured) metal.

The results of the acceleration were captured using time lapse photography in a microscope.

There results are published Time-lapse photography of the β-Sn/α-Sn allotropic transformation in the Journal of Materials Science: Materials in Electronics, doi: 10.1007/s10854-008-9739-5. Seems to currently be published ‘online first’.