Materials Engineering Puzzle

With all of the tech prowess around here, I’ll bet there are a few out there that can identify what this sample of steel and copper represent.
Close up of cross section interface of 1/2" thick steel and 1/8" copper.
Hint; a method of joining dissimilar metals.


I remember watching an episode of Beyond 2000 back in the day (one of the coolest shows ever!), and some scientists found that you can unexpectedly combine dissimilar metals by using explosives. Fused them together as if they were one piece, even titanium + aluminum.

But those ridges don’t match up with that, I don’t think. Sooooo…I dunno.


I want to say it’s some type of cold / pressure welding. But I’m not totally sure.

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Fry pan? :stuck_out_tongue_winking_eye:

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Friction welding?


Generally you braze one metal to another using flux of some kind, don’t you?

So what is it? (Inquiring minds want to know.)

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Here is a little more on that.

its a sweet process but i dont think you would get the toothed pattern you see.

Personally i have no idea what would form that funny pattern, but then also have that void.

Not friction welded
not explosion welded
not regular welded

Ultrasonic weld?


Electromagnetic pulse welding?

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All good guesses.
@nunzioc - Bingo! Explosive welding.

A final project in my Son’s metallurgy and materials engineering class at Colorado School on Mines.
The metal plates were 12" square, and the copper “flyer” plate was spaced 1/8" above the steel.
The explosive was spread evenly across the top to 1/2" deep, and topped off with sandbags.
After detonation everything was gone.
After a few minutes the plate was located 50’ away. Bear in mind, the plate wasn’t blown up into the air, it was bounced off the ground!

The process is fascinating. The explosive was triggered at a convergent point off of the plate so that it spread to the width of the plate before propogating across it.
So the flyer is slapped down from one side to the other, violently evacuating the space between the plates, creating the “jet” of gas that scours both surfaces as it is forced out.

Electron scanning microscope of the interface shows how the metals mixed. I was astounded to see spheres of each metal in the other! I couldn’t believe there was time for that to occur in the instant it took.

I expect the difference in surface texture you saw @nunzioc was due to different material characteristics.
the void there is one of the sites where a sample of metal with a known melting point was positioned.
The experiment was an attempt to determine the Max temperature reached, but results were inconclusive.

Thanks for playing!


One of these days I want to dissolve/etch away the copper to see the wave pattern on the steel!


Explosive welding is so neat. I wish I could have gone to this camp when I was young:

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I have a welder friend that used to weld 1/4" aluminum and steel angle together along the seam to the amazement of all observing. It is the different thermal expansion characteristics that make this so difficult. Upon cooling, one would normally see the joint self destruct due to the mismatched forces. The secret is to use a welding rod with intermediate expansion characteristics that can bridge the two dissimilar materials. In my mind, using explosives creates a similar effect at the interface between the materials, allowing them to join.


In my hometown they build destroyers and it’s used where they need to weld steel and aluminum together. I heard it’s made out in a desert somewhere. It must be a lot of fun to make!


Interesting! I would have bet money he couldn’t do it!

@mad_macs, considering the nature of the operation I can understand doing it in the middle of nowhere!
I guess cladding is one of the few applications where it shines!


:grin: :grin: This was fun! Thanks for posting it…

And soooo cooool…had no idea about the ridges; thought that it was proof that this was something different instead.

And if I recall correctly, I think it actually started out with an artist using it to make cool designs in metal; two pieces that would be slammed and create a cool indentation / engraving, and then it was realized that it could weld dissimilar metals.

Btw, this is the second thing that I’ve been able to name from that show…I remember in the building where I worked as an intern in an office, there was also a Doctor’s Office…and one day I’m coming back from going to drop off the mail, and I see a couple of doctors with a patient in the lobby, and his foot is hooked up to a computer and monitor, and it’s displaying the pressure on his foot as he stands and walks in different colors (sort of like an infra red pic). They were trying it for the first time, saying how amazed they were at what it revealed, etc. I shouted out in my excitement: “HEY!! I KNOW WHAT THAT IS FOR…DIABETES TREATMENT!”. (There was no one else there, so no privacy concerns).

The look on the doctors’ faces was priceless…like “How, in the name of God’s good green Earth, does this 19 year old kid know what this piece of cutting edge super technology is???”

I don’t remember if I told them how I knew, or if I just walked away smiling…lol :smiling_imp:


That is an amazing feeling, to be sure. I once got into a bit of trouble by offering an intuitive guess as to how a defense contractor had achieved a super high pressure gas cylinder for space use. I blurted out it must be via titanium aluminide super alloy and was immediately taken aside and grilled as to how I could know such things. I shocked him when I said “If you think that’s something, you should see what it does when exposed to microwave plasma”. It was both a very good and very bad day for me after that.


That’s epic! Would love to have the brains to work in such a field. If you don’t mind me asking, how did you know / what do you do (if you’re even at liberty to say)?

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Surprised there wasn’t a job offer involved…

I am an independent researcher, you know kind of a MacGyver/DaVinci/Indiana Jones wannabe. I have traditionally excelled at, and were inspired by, things others said were impossible to achieve. My mistakes are many, but I learn from all of them and I dare to dream big. This specific research was centered around a thought experiment to speculate how one could propel a spacecraft using only the materials alleged to have been found at Roswell, i.e. memory alloy foils, fiber optics, etc, and to advance my theory that coherent fields modify spacetime and that the technologies required for warp drive exist today.


Oh…well, yeah, of course…duh!

LOL. Second time today that I’m speechless on this forum…amazing.