Metallurgy and the iron–carbon diagram – Metal Technology and Design notes (ZIMSEC A Level)

Metals are crystalline: body-centred cubic (BCC – ferrite, chromium), face-centred cubic (FCC – austenite, aluminium, copper; more ductile), and close-packed hexagonal (zinc, magnesium). Grains form as metal solidifies; smaller grains give higher strength and toughness. Dislocations moving along slip planes allow plastic deformation; cold working increases dislocation density (work hardening).