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Comment by Cthulhu_ | Hacker News Reader

Well, they knew the effect existed, so applications are already in use; this just explains the how, which I'm sure makes the effect more predictable - and allows for researchers to find more alloys with this effect in a focused manner, instead of via trial and error.

As for applications, it probably won't be garden variety appliances, thermal expansion isn't much of an issue there and designs for all of the things you mentioned have been tweaked a hundred years ago to deal with thermal expansion (although railroad tracks are still an issue sometimes). And of course there's other parameters, like wear resistance; nickel is a pretty soft metal I believe.

But, things like precision industry or space will find a use for this. Sattelites have to deal with hundreds of degrees of temperature variation.

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Invar is actually a very bad material for most uses, because having zero CTE usually won't match the rest of your system's nonzero CTE. So things will fail pretty quickly.

Matching CTE is a big deal in careful engineering. "Alloy 42" is a great example of that in action: it's an invar-like alloy with its CTE matched to silicon, so chip lead frames expand with silicon dies as they heat up during operation. Not that many things use lead frames anymore....

What do you mean? MOST ICs use lead frames still. Although there is a large push in consumer electronics to use flip chip or CSP devices, I would suggest that most devices are still using lead frames. Any plastic packaged device is lead frame based.

Sorry, you're right, I was thinking of the newer stuff (flip-chip, wafer-scale, nearly-bare-die, etc). It's also interesting just how few leadframes are magnetic these days, even for something ancient like a SOIC-8. I don't know what they use; I guess it's not very important if there isn't much power dissipation.

I disagree, even modern cars have a lot of unsolved problems with thermal expansion and cracking causing failures of cylinder heads, gaskets, exhaust manifolds, turbochargers, etc.

It may be solved in principle, but certainly not in practice.

There are problems that are game stoppers and there are problems that are unavoidable. Cars work. Yes, if you drive 1 million miles you will have cracks in the engine due to thermal expansion, but who cares? Make a new engine and get over it.

Now consider a space elevator. Material problems are a game stopper.

These problems are already solved for very high end aftermarket exhaust systems, which use Inconel.

"Modern" cars run on electricity and don't have any of those parts or their corresponding problems.

Your "modern" cars have cooling loops for their battery, therefore cyclic thermal fatigue.

Plus the bearings, heat from (regenerative) braking, and I'm sure a few other parts.

I think the important bit is that this isnt 'a lot' of systems, it is comparatively few.

I haven't looked it up, but I'm sure the magnitude of thermal cycling in a battery is way less than in a combustion engine.

I didn't even know that they didn't have a good explanation related to magnets, as invar for example has a curie point, above which it loses it's neutral thermal expansion properties.

I've seen it used for low temp things or tooling but for that reason it can't be used for anything really high temperature.

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