This question has been posed a lot but there is only one short answer – the Marvel cinema universe has no licensing rights to use a material called "Adamantium". This word was licensed to the X-Men universe (the material that was introduced into Wolverine's body)
The werewolf wolf with Adamantium nails.
Therefore, the word Adamantium is not used by the MCU authors. Because of Captain America's 342 story, the Captain was given a shield by a Black Panther using a Vibranium alloy, which is the right solution for this difficulty.
Excerpt from Captain America No. 342, this is where Steve was handed the shield from Vibranium from T'challa.
For the Marvel cinematic universe, this Vibranium shield also withstands the rigors of war and is enough to be included in the list of legendary weapons of this world – until hit by Thanos's wrath. shattered.
According to 303 was released in 1985, we were able to see MacLain again, in my opinion the creator of Captain America's shield.
Another Captain America shield that is well loved by the audience is the result of a combination of Vibranium and Proto-Adamantium – a mixture that makes it nearly impossible to destroy in the comic universe.
Only creatures with the ability to transform reality can afford to make it unstable enough to destroy – including Molecule Man, Borson brothers (Odin or Cul) or images like Galactus enough to reverse the process of creating this shield.
Cul Borson, brother of Odin.
Finally, because the word Adamantium is associated with Captain America in the comic universe, the film universe's author team must change accordingly because they are also unable to overcome legal and major problems because So, the shield is made from Vibranium.
A symbolic weapon for Captain America's patriotism, the shield survived 21 films.