I would like to know what combination of ingredients resulted in the formation of Proto-Adamantium?
Captain America's circular shield is composed of an unknown alloy dubbed Proto-Adamantium. Technically, the explanation is the material was being designed to be a super-strong metallic alloy that Vibranium was added to. After the scientist creating it took a nap, he woke to discover his mixture of Vibranium-altered meta-material was somehow viable and he poured it into a mold before it hardened.
He later attempted to recreate the process with no apparent success until he stumbled upon his next greatest creation, Adamantium. Virtually indestructible but still apparently no match for his first creation, Proto-Adamantium of which there was only one supply on Earth: Captain America's shield.
Captain America's shield has been destroyed on very few occasions and in its most recent destruction it was reforged by the Dwarves of Asgard with a bit of recently added Uru metal). This has returned the shield to its position as one of the most indestructible items on Marvel's Earth-616, the primary continuity of the comic Marvel Universe.
The shield from the Marvel Cinematic Universe, Earth-199999 is composed entirely of a vibranium metallic alloy. It is proven to be tough enough to survive a strike from Thor's hammer, Mjolnir. It has never been determined if it is as strong as the Proto-Adamantium shield of the comic universe.
In 1981′s Captain America #255, we learn that Cap’s shield was the result of a metallurgical accident…
The process that lead to the creation of the circular shield has never been able to be duplicated and the scientist who discovered it would later be credited with the creation of the next best, most indestructible metal of the Marvel Universe, adamantium.
Given that the Dwarven smiths of Asgard were able to reforge and repair the shield, it can be inferred their level of technological capacity exceeds Human technology significantly since Adamantium cannot be forged, altered or even affected by anything less than significant cosmic energy, matter manipulation or reality-altering powers.
Through retroactive continuity, it is established that the shield was presented to Rogers by President Franklin D. Roosevelt. The shield is created by a fictional American metallurgist named Myron MacLain, who had been commissioned by the US government to create an indestructible armor material to aid the war effort. MacLain experiments with the vibration-absorbing metal vibranium. (Captain America vol. 5, #5; May 2005)
During one of his experiments to fuse vibranium with an experimental iron alloy, MacLain falls asleep and awakens to find the experiment a success. This is due to an unknown catalyst entering the process during his slumber, and he is unable to duplicate the result.
The vibranium-iron alloy mix is then poured into a mold for a tank's upper hatch to create the disc shape and painted to become Captain America's symbol. MacLain would later attempt to recreate the shield's metal to no avail, his experiments instead eventually yielding the super-metal adamantium.
The extra-terrestrial material vibranium bestows by nature of the curvature and density of the element within the shield its ability to either deaden or absorb vibration-based energy used against the shield when struck along the front of the shield.
The shield is capable of absorbing incredible energies and preventing them from reaching the wielder. Cap has even used it to absorb the impact of falling from a skyscraper and absorbing the energy of his landing with the shield escaping serious injury.
The adamantium/iron/uru element of the shield supposedly renders the shield relatively invulnerable to almost any energy or effect not considered cosmic or reality-altering in nature.
The nigh-indestructible shield has been broken five or six times, in continuity, by the Molecule Man, Doom, imbued with the Beyonder's powers, Thanos, wielding the Infinity Gauntlet, Thor using the Odinforce and by the Serpent, brother to Odin. Its breaking is usually a monumental event and when its replaced or repaired it is often by the same force that destroys it.
In 1985′s Captain America #303, we meet MacLain again, who, we learn, created Captain America’s shield…and yes, in MacLain notes we learn the shield is composed of something-something/vibranium/iron alloy. We are never told what the X-element which allowed proto-adamantium to exist.
The exact origin of Pro-Adamantium was never mentioned in comics. But I believe that the unknown catalyst/X-factor in the mixture must have caused a chemical-molecular reaction between Vibranium and the experimental iron alloy. The process must have converted the iron alloy into Proto-Adamantium and at the same time allowing the Vibranium to fuse. That scenario could be the reason behind the existence of Proto-Adamantium.
None of the Adamantium existed before Vibranium. These two metals have a mutual relationship at a molecular level even though they have different physical properties. Since Vibranium can only be fused with Adamantium that includes Proto-Adamantium.
In early days scientists named the shields composition as Vibranium-iron alloy. But now it is referred to as Proto-Adamantium and Vibranium alloy, with the discovery of Proto-Adamantium. It was revealed that the experimental iron alloy ultimately became Proto-Adamantium in the bonding process since there is a historical link between Proto-Adamantium and True Adamantium which resulted accidentally in an attempt to replicate the shield.
According to Marvel Comics Database the official metal found in Captain Americas Shield is Proto-Adamantium and the official composition is Proto-Adamantium and Vibranium alloy. When the shield was reconstructed after being shattered by the Serpent it was infused with the Asgardian metal Uru making it stronger than ever. With the addition of Uru to its composition the shield is now an alloy of Proto-Adamantium, Vibranium and Uru.
Proto-Adamantium is the original Adamantium created by Dr. MacLain. It is even denser and stronger than True Adamantium and it can never be replicated.
The two metals in the shield works in concert with each other. The Vibranium in Cap's shield absorbs vibrations and kinetic energy. At the same time Proto-Adamantium in the shield makes it almost completely impervious. Together these two metals in Captain Americas Shield makes it the most invulnerable item in all of existence in terms of pure durability. Only a godly force can actually damage the shield other than tampering with its molecular structure. The star and stripes of the shield are made of an enamel, that can stand temperatures of up to 9,000 degrees Fahrenheit.
This ultra tough super alloy in the shield has its own unique properties that neither metals (Adamantium or Vibranium) seem to posses. Such as being able to deflect energy waves, including certain mystical energies and being lightweight as well as aerodynamic. The recent addition of Uru to the shield could have the possibility of carrying an enchantment.