Metal that grows stronger in the sun

Metal that grows stronger in the sun Australian CSIRO scientists have discovered a process that could lead to the production of aluminium cars and planes that get stronger as they bake in the sun.

Dr Roger Lumley of CSIRO Elaborately Transformed Metals says the new process involves age-hardening aluminium to a point where the process can be completed by exposure to sunlight rather than in a furnace. The discovery arises from CSIRO's work in light alloys and advanced metals.

"We found in the course of this work that if the high-temperature aging process used to strengthen aluminium components, such as castings or motor vehicle body panels, is interrupted, and the material is allowed to undergo secondary aging at ambient temperature, the material became 20% tougher" Lumley said.

At the same time, the total-energy-to-rupture point can also be extended by up to 800%, resulting in safer cars with crumple zones able to absorb much more energy as they deform or rupture on impact.

"Significantly it means aluminium car body panels, for example, can be assembled and painted, (the baking cycle used to harden the paint adds to the process) and they will continue to strengthen in the sun.?

"The process would continue, albeit at a slower rate, for the life of the vehicle" Lumley said.

Reply to
mastic
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On Thu, 03 Jun 2004 23:23:44 +1000, mastic vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email

What's the use of that in cars? The body is supposed to crumple?

We already get cancer from the sun. So now we get brain damage and broken bones?

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Sometimes in a workplace you find snot on the wall of the toilet cubicles. You feel "What sort of twisted child would do this?"....the internet seems full of them. It's very sad

Reply to
Old Nick

That's code for "collapse with progressive resistance." Yes, a unibody structure is supposed to crumple.

Age-hardening or age-strengthing aluminum is nothing new. What appears to be new is an alloy that hardens so much at those temperatures, quickly enough to be useful.

Ed Huntress

Reply to
Ed Huntress

I gathered that it was a change in the process: namely that stopping the articifial hardening in its tracks and letting it complete at ambient gives better results.

So what, will we have 6061-T7? ;)

Tim

Reply to
Tim Williams

More than likely the body panels you are speaking of are not load bearing from a crash perspective. Hoods, fender, outer sheet metal in general doesn't play a role in crash energy management. In the auto business, hoods and fenders are increasingly made out of aluminum. The underlying body structure is still very much steel. There are of course exceptions but in general most/all high volume mass produced vehicles have a steel body structure.

Reply to
gradstdnt

Well, I think the idea here is that a practical, low-cost form of age-hardened aluminum would likely replace a lot of structural pieces in a unitized body/chassis structure, as well as the skin.

The skin is not much of a problem to begin with. Age-hardening doesn't make aluminum any stiffer, only stronger.

Ed Huntress

Reply to
Ed Huntress

It gets stiffer, too. We use 2017 AD rivets in aircraft repair, and those suckers are supposed to be stabilized. However, if they are in stock too long they get pretty hard and won't buck properly at all. Some outfits will warm them up to 300 or 400 degrees to bring them back to the softness they had when new, and they'll stay that way for a few days.

Dan

Reply to
Dan Thomas

You need to distinguish between hard and stiff. Stiffness is dependent on elastic modulus which is approximately 10E6psi for all aluminum alloys in all tempers. Hardness and strength can be all over the map.

Ted

Reply to
Ted Edwards

This is an age-old problem in explaining metals properties, and in definitions. Ted gave the engineers' answer. The meaning of it is that "stiffness," in this context, means the ability to resist bending up to the point where the metal is permanently deformed.

Most metals are equally "stiff," in these terms, no matter how hard or strong they are. Steel and aluminum are among them. If you make a body panel of a certain thickness out of one of these metals, its resistance to springy bending and oilcanning is the same whether you harden it or not. Its resistance to taking a permanent dent, or a permanent bend, on the other hand, will vary widely depending upon how hard (and thus, how strong) it is.

Rivets are a confusing example because you're looking at permanent deformation, which is a function of strength, not of stiffness.

It's a subject that requires a lot of examples before the concepts sink in. It took a lot of study before I was ready to accept it, because it isn't intuitive at all.

Ed Huntress

Reply to
Ed Huntress

Damn. There's an example of why it's hard to explain this subject clearly. I think I just gave a misleading impression.

I meant to say that an *individual* metal has roughly the same stiffness, regardless of hardness or strength. But steel, in all grades, is roughly three times as stiff as aluminum (in *almost* all grades). The stiffness (elastic modulus, or Young's Modulus) of mild car-body steel is almost exactly the same as fully-hardened tool steel, even though their strength may differ in a ratio of 8 or 10 to 1.

Ed Huntress

Reply to
Ed Huntress

Thanks for the clarification. As you say, it's not intuitive.

Dan

Reply to
Dan Thomas

On Thu, 03 Jun 2004 16:03:38 GMT, "Ed Huntress" vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email

Sorry. Should have smilied this one.

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Sometimes in a workplace you find snot on the wall of the toilet cubicles. You feel "What sort of twisted child would do this?"....the internet seems full of them. It's very sad

Reply to
Old Nick

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