Materials
Materials science links a material's structure to its mechanical, thermal, electrical, and chemical properties, guiding selection for a given application.
Mechanical Properties
Stiffness is the modulus of elasticity (about 200 GPa for steel, 70 GPa for aluminum); strength is the stress at yield or fracture. Ductile materials deform substantially before failing, while brittle materials fracture with little warning.
Thermal Behavior
Materials expand when heated: delta = alpha·L·(delta T), where alpha is the coefficient of thermal expansion. Restrained expansion produces thermal stress, an important consideration in bridges, rails, and piping.
Phase Diagrams and Selection
Phase diagrams show which phases exist at a given temperature and composition, governing heat treatment of alloys. Material selection balances strength, weight, cost, corrosion resistance, and manufacturability.