Dislocations, Crystal morphology, Grain morphology, Microstructure, Carbon steel, Low-alloy steel, Structural steel, Hardenability testing, Precipitation hardening, Annealing, Austenitizing, Normalizing, Oil quenching, Water quenching, Austempering, Martempering, Tempering, Chemical composition, Rate of decomposition, Hardenability, Fracture toughness, Hardness, Plastic deformation properties, Tensile properties, Heat transfer properties, Recrystallization temperature, Phase, Phase transformations, Heat treatment