Attack Speed is a property of Weapons. Despite the name, it is not used to determine the actual attacking speed of weapons in-game. Different weapons have different displayed Attack Speed. The related Attack Speed Modifier is a Property of Materials that changes the attack speed of Weapons that are made from the Material.
The Attack Speed Modifier affects weapons that can be made from different Material types, and changes their displayed attack speed number. The Attack Speed of a weapon does not affect the actual speed at which the weapons attack[1], nor does it affect the Artifacts that are made from the Weapons.