WWII ship and tank explosive bonding discovery

Post-explosion discovery that bomb blasts had perfectly bonded sheets of metal. DuPont (Revolutionary-War-era gunpowder origin in Pennsylvania-Delaware) led postwar research.

There are other types of cold welding I'd forgotten I had. One is explosive bonding. This was discovered during World War II — bombs would go off on ships, or blow a tank apart, and they would find two sheets of material bonded together perfectly by the explosion. They did a bunch of research after World War II. DuPont did a lot of it, because DuPont started in the Revolutionary War making gunpowder, and they are still a big — most of the explosive plants in the United States are in the Pennsylvania-Delaware area, because that's the home of DuPont, where explosives manufacturing got its start in the late 18th century.