I’ve got a historical material science / metallurgy / applied physics itch I’d really like to scratch, but it falls far beyond my (relatively meagre) physics skillz. I’ll describe the challenge as best I can, (hopefully) enough for one or more potential physicist collaborators to step forward to help me move the whole narrative forward. Thanks!
The Alloy Challenge
The scenario: the year is 1937, and you are a highly-skilled metallurgist. You have just been handed an ingot of a little-known (and incredibly expensive) shiny new alloy.
The challenge you have been set by your bosses:
- How would you fashion this into a foil? (You can do this however you like)
- How would you predict (and then measure) that foil’s tensile strength?
- How would you join pieces of that foil together (e.g. brazing or riveting) so that the lap tensile strength isn’t significantly weaker than the foil’s tensile strength.
To help you, you can assume you have a copy of the First Edition of Hansen’s (German, later translated into English) “Constitution of Binary Alloys”, along with a state-of-the-art-for-1937 laboratory / technical library. 😉
Email me (nickpelling at nickpelling dot com) and I’ll tell you the alloy! Thanks!
My first pick would naturally have been duralumin, even though it had been around since 1910 as opposed to Nick’s ‘little known’ in1937 but, I can amagine later versions, probably improvements on the original recipe may have been called hitlerite or something with a nazi connotation.
Napoleon’s baby had an aluminum rattle… even though it might not be the public recipe we are used to, if you looking among guild libraries of the time, you might find a trade secret or two that would be of use. Also, aluminum comes from bauxite. And, if you really want to think out of the box, look among the companies producing clear glass at the time. That was the whole “Star Trek IV” joke about transparent aluminum. (Ok, I’ll hide my pointy “thinking ears” now…!). But, historically, there are other types of foil — such as gold — that always had a lot going on with them. The real question is tensile strength after the first 100 smelts. It is, after all, an alloy — which is a blending of metals. If you play with it too much, it will start to reduce to its base components, especially if you do so at the wrong temperature, because you would be slowly skimming dross…(So what is the ultimate use — Military mass production? Commercial canning industry? Dental fillings?). Just a few thoughts on the question. You can keep this answer private it you want, because it is rambling— but I hope it provides you with a smile and some decent conversation.
At first glance, based on the data, I would guess nickel silver (monel). (Copper, nickel, zinc alloy)
But it is older than 1937.
It is very shiny and looks like silver. But it is an alloy.
It is often used in casting. Many windows and door handles (the silver ones) are made of this material today. Coins were also minted in the past.
It is easy to roll into foil, and as a connection in the foil, overlap and glue. It is difficult to weld. Riveting would be possible, many rivets are made of this material. Especially with non-rusting materials.
https://en.wikipedia.org/wiki/Nickel_silver
Translated with http://www.DeepL.com/Translator (free version)
Children’s rattle made of aluminium in Napoleon’s time.
Yes, aluminium was worth its weight in gold then.
Who would have thought that we would make beer cans out of it?
There seem to have been several tried and tested means of joining metal foil devised so as not to diminish tensile strength from about the period of Nick’s set period., e.g., simple pressure firmed lap folding or rolling, various rivetting and welding techniques that were also around in 1937; But, most efficient of all that comes to mind would be the ultra clever combi rivet/clinching method developed by the nazi’s in the late twenties (?) for their new improved aerodynamic metal skinned Fokker aircraft applications.
From an ET crash? Hmmm…
Matt
Here you would first have to determine the thickness of a film. But here the thickness of exactly this film.
Thin sheets are approximately 3.0 – 0.25 mm.
Aluminium foil is about 0.02 mm thick. It is also available up to 0.005 mm.
Riveting is out of the question here. Welding around 1937, no chance. You need a special plasma process for this.
A spark from a normal lighter would burn a hole in it.
Gold leaf, even without glue, cannot be removed from the fingers without tearing it.
How thick would this foil be?
https://en.wikipedia.org/wiki/Aluminium_foil
Translated with http://www.DeepL.com/Translator (free version)
To stay with the year 1937, I would see the connection of a foil with this procedure.
Before 1940. 1937 possible.
https://de.wikipedia.org/wiki/Kaltverschwei%C3%9Fen
Titanium would be another candidate.
It has been known for some time, but the patent for the processing is confirmed from 1938, 1940.
It is no longer possible to imagine aircraft construction and space travel without it.
Apart from radioactive materials, I’m running out of ideas. They are all from around 1930 -1940.
Don’t know what it’s called but, I’ll hazard another guess and go for something with a high Wolfram content eg., Titanium, nickel and ferous alloy, able to be fused then beaten or rolled and made into a thin foil material. If that doesn’t work for Nick, I’ll take my physisictic credentials elswhere.
Guess I’ll stick with duralumin or a like composit bauxite/copper based alloy if that’s OK with management.
I wonder which companies had the equipment to mill metal to the thickness of foil? Perhaps they had also produced the anti-radar foil used in WWII?
Here’s a photo of WWII anti-radar foil. Not very wide it’s true, but pretty thin.
https://www.warrelics.eu/forum/attachments/docs-paper-items-photos-propaganda/80799d1312773522t-chaff-aluminum-foil-fool-radar-pict0008.jpg
Ok, I’ll bite.
I am a physicist (although this question is really about history of metallurgical engineering), and I am a very occasional lurker of this blog. I notice that most of the other replies are speculating about the nature of the alloy, rather than answering Nick’s questions. So, I’ll have a go. I split this up because each part is somewhat long.
0. The question Nick didn’t ask: if I wanted to know the composition of the alloy, I would use atomic spectroscopy. In 1937 this was a much slower and fiddlier method than today but still an extremely powerful technique. With two caveats, you would get a list of all the elements in the alloy, and their approximate proportions. Caveat 1: you only get composition, not structure; if the alloy is inhomogeneous (e.g. a multilayer foil or a MMC), you won’t discover that fact. But in 1937 no-one knew about such materials anyway. Caveat 2: you could detect elements that had not yet been discovered, but not identify them. However, with the identification the spectrum of technetium in 1937 there were only 3 cis-uranics left. All of which are too unstable to assemble a visible quantity, never mind an ingot.
1. I believe that in 1937 there were only two methods to turn an ingot into a foil: the ancient method of hammering, and the more recent (but still very mature) rolling mill. (There are other methods now, but all the others I can think of were invented post-WW2.) Rolling mills produce superior results to hammering because the stress and deformation of the metal is much more uniform. So, you would more likely see rolling for an industrial process, with hammering used in artisanal processes and small scale tests. There are lots of variations according to the properties of the alloy. Rolling may actually start with (steam) hammering to get a billet into a rough plate shape so it can enter the first stages of the rolling mill. Softer alloys can be cold rolled but most rolling is done hot, which increases the metal’s malleability. Conversely, hammering may start by sawing, cutting or slitting off a small piece of the billet because hand-hammering can only work on small amounts at a time.
For very thin foils, the workpiece might be protected by a supporting material; which generally must be a material that does not adhere to it under pressure.
2. So far as I can determine, in 1937 you couldn’t predict the tensile strength of a new alloy with any useful degree of reliability. Indeed, even today the theory is very incomplete. You would measure the tensile strength with an instrument that goes by the fancy name of “materials testing machine.” This is is simply a machine that applies gradually increasing force to a test sample whilst logging both the force and the deformation in the sample. However, there is a big catch with testing a foil. Test pieces have to be shaped into particular forms that guarantee that there are no concentrations of stress that will cause early failure. The standardised shape used for tension tests cannot be made from a foil, and it is not at all obvious how how a foil could be mounted in 1937. (Today, we would use high performance adhesive to attach either end to a metal plate which would then be bolted to the tester, but in 1937 the glues probably weren’t strong enough.)
I don’t know much about what jointing technologies were available in that era, so this is a bit more speculative. Three suggestions are roll bonding, clamping, and glue. Let’s start with glue.
The thing with gluing the foils is that the area in shear loading in a glued joint is many times larger than the cross-section in tension. Thus the glue can be inherently much weaker than the metal, yet the joint still as strong as the foil. For example, consider an aluminium foil 10 micron thick by 10 cm wide, with a UTS of 275 MPa. Therefore, the maximum tensile load will be 275 N. Now suppose the area overlapped for gluing is 5 cm. This will be at least as strong as the foil if the shear strength of the glue is 55 kPa, which is not very strong at all.