This document discusses materials selection criteria and common materials used in automotive, aerospace, marine, and defense applications. The key criteria for selecting materials include performance requirements, reliability requirements, and size/shape/mass constraints. Common automotive materials are steels, aluminum, magnesium, copper, plastics and carbon fiber. The most used aerospace materials are aluminum alloys, titanium alloys, high-strength steels, and composites. Ceramics are mainly used as armor materials in defense, while alloy steels are most common for tank armor.