Materials Science: Why Things Break

A perfect copper crystal should yield at 7 GPa and real copper gives way at 10 MPa, and closing that gap took thirty years and produced most of modern metallurgy. This path builds mechanical behaviour from defects: dislocations that let metals bend and ceramics shatter, cracks that make a part fail far below its yield strength, and the material index that ranks candidates for a job instead of ranking them in the abstract.