The microstructure of precipitation-hardened alloys: The dispersed phases present in metals; The thermodynamics and kinetics of ageing; Characterization of microstructure of aged alloys; Quantitative metallography; Quantitative metallography. The strength of aged alloys: Alloy designations; Hardness; The tensile yield stress; Process modelling of age-hardening; Work-hardening behaviour of precipitation-hardened alloys; The achievement of strong precipitation-hardened alloys. Fracture behaviour of aged alloys: Introduction; Slip distribution in alloys containing particles; Fracture under tensile load; Failure of precipitation-hardened alloys during forming; Fatigue of precipitation-hardened alloys; Stress Corrosion. The strength of alloys at elevated temperature: Strength of microstructures where particle by-pass by dislocations operates; Yield strength of microstructures where particle shearing by dislocation operates; Creep behaviour of precipitation hardened alloys; High-temperature fracture of precipitation-hardened alloys. Appendix.