i was given this sample piece by a retired naval architect ,he is very old and can't remember details but it's some kind of friction weld process with "teeth" it's clever can anyone expand on my limited explanation? Happy new year to all.
I used to have a sample of that on the desk as a paperweight, its a transition joint for joining steel to aluminium, a piece of ally and a piece of steel explosive welded together, commonly used in shipbuilding for welding ally cabins onto steel decks.
Here you are http://triplate.com/