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Suppose an advanced technological civilization colonizing a planet/planetoid which has very little iron. Suppose the surface is mostly rocky with a lot of $\text{SiO}_2$. There is also some carbon and limited amounts of other metals (Nickel, Zinc, Manganese), but only silicon and carbon are available in large amounts.

Would it be possible to fully replace iron and other metals as structural materials in building habitats, bridges, vehicles, machinery, machine tools, electrical equipment, jet propulsion engines etc?

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    $\begingroup$ Iron is abundant throughout the universe. It would be very odd if a planet large enough to be habitable had negligible amounts of accessible iron, and even odder if other bodies in the same solar system (particularly asteroids) couldn't make up for it. If a civilization is advanced enough to colonize other worlds then asteroid mining should be straightforward. (Not saying you couldn't have this in a SF scenario, just that it needs substantial explanation/hand-waving.) $\endgroup$ – Royal Canadian Bandit Nov 9 '14 at 22:25
  • $\begingroup$ @Royal Canadian Bandit it is possible the planet is covered with ica with only some $\text{SiO}_2$ rocks available here and there from under ice. And they have no functional spacecraft. $\endgroup$ – Anixx Nov 9 '14 at 23:52
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The other answers largely deal with the structural aspects of iron. But there is another property of iron which is widely used: it's magnetic permeability. If you wrap a conductor, such as a copper wire, around a chunk of iron, then pass a current through it, the iron atoms will align themselves with the resulting weak magnetic field, thus amplifying it into a much stronger field. This is the basis behind electric motors and generators, and without abundant iron this line of technology will be severely stunted.

It looks like there are some other metals that may provide a similar, but weaker, effect -- such as nickel, manganese, or gadolinium. But most of the magnetic cores we use are based to some degree on iron, whether in pure form, as an alloy, or as a ceramic. Even if you find alternative materials, the fact that they aren't as ubiquitous or efficient as iron means any such technology is likely to be rare and/or expensive.

It is also the basis behind magnetic storage, such as tapes and hard drives. I was going to suggest that such a civilization might jump straight from vinyl records to optical CDs. But then I remembered that microphones and speakers also rely on magnets, so audio systems in general might not be very common (and this is just one example of how common magnetism is).

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  • $\begingroup$ There is such thing as electrostriction that may be used to produce sounds. $\endgroup$ – Anixx Nov 10 '14 at 9:35
  • $\begingroup$ And also solid state hard drives. But, more than just replacing iron with a different material, this is replacing the functionality of some types of devices with alternate devices that work on possibly different principles. $\endgroup$ – Caleb Hines Nov 10 '14 at 20:51
  • $\begingroup$ Traditionally, microphones and speakers use electromagnetism, but there are alternatives. Early microphones used carbon granules as a pressure-sensitive resistor, and piezoelectric materials can be used as either a microphone or a speaker. $\endgroup$ – Mark Nov 10 '14 at 23:39
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Sure. In fact humanity on earth had similar stages - the copper and bronze ages. You don't need iron for storing electricity or producing it electrochemically (though modern mechanical power generation, and transformers do rely on soft iron cores - an air core is plausible but less efficient).

If you had electricity, you might be able to directly go from a copper based civilisation to one that uses aluminum or titanium (which are extracted electrochemically)

An alternative might be to forgo metals altogether and go for a ceramics based civilisation. While they're brittle (with more primitive designs), they're easy to make, fairly hard wearing, and you can build off a ceramics based tech base to start with. You might also use glass cutting tools - glass knives are used in surgery, and ceramic knives are 20th century technology.

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The answer in general is yes: you can do metallurgy without iron. Iron based metallurgy just yields alloys that have good price/weight matches in a modern Earth economy. There's plenty of other alloys, some are much more impressive than iron based ones!

However, when you start talking about "replacing iron," now you're making life harder on yourself by insisting they develop the same kinds of technologies we did, and in the same order. I would expect everything they build would reflect the availability of different strength/weight/cost materials. They could build the things they need, but they would choose to approach designing them differently.

I am reminded of The Neil Stephenson book, Diamond Age. In there, nearly everything was made out of diamond because their nanotech tools made it easy to make carbon bonded objects in any shape they please.

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  • $\begingroup$ Suppose the civilization like ours (iron-itilizing) land on rock-only planet. I wonder what exactly alloys of silicon and/or carbon with small amounts of other metals they may use. I hears silicon is very hard so not always suitable for iron replacement. $\endgroup$ – Anixx Nov 9 '14 at 23:15
  • $\begingroup$ What technology level? Obviously we are not at a spacefareing technology yet. And also, how long after landing do they have to adapt to new materials? If their technology is advanced enough, metamaterials offers a WHOLE different direction to go in as well, less focused on the alloys and more on the structure. $\endgroup$ – Cort Ammon Nov 9 '14 at 23:32
  • $\begingroup$ I just did some minor wikidiving: Sililum is a very popular alloy in the automotive buisness - Silicon and Aluminum $\endgroup$ – Cort Ammon Nov 9 '14 at 23:39
  • $\begingroup$ Do u mean silumin? It has more aluminium than silicon. $\endgroup$ – Anixx Nov 9 '14 at 23:43
  • $\begingroup$ Alternatively, if you want to focus on details of how to replace steel with other alloys, and only consider that approach, we might want to open up multiple questions for replacing different things "such as one question for bridges." It is highly unlikely that one alloy would replace steel in all possible uses. Focusing on one use would permit much more detailed exploration. Focusing on "replace everything iron does" requires a more cursory high-level pass. Answering that question satisfactorily might take decades of research. $\endgroup$ – Cort Ammon Nov 9 '14 at 23:51

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