Introduction to Aluminum and Aluminum Alloy Materials Aluminum is the most widely distributed and abundant metal element in the Earth's crust, accounting for approximately 7.3-8.3% of the total mass of the crust, second only to oxygen and silicon; Aluminum was discovered in the early 19th century and began to have production scale in the early 20th century; Hard aluminum alloy was invented in the early 20th century and was widely used in the military industry during World War I.