37th John Player Memorial Lecture Design of strong, tough & affordable engineering alloys

Fe Ru Os Hs 6d 2s

ferrite  austenite 

DISPLACIVE RECONSTRUCTIVE

c r  s 1

Surface 1 Surface 2 Srinivasan & Wayman, µm

UPPER BAINITE (High Temperature) LOWER BAINITE (Low Temperature) Carbon supersaturated plate Carbon diffusion into austenite Carbon diffusion into austenite and carbide precipitation in ferrite Carbide precipitation from austenite

Temperature / °C Decarburistion time / s Fe-0.4C wt%

Ae3' T' o x Carbon in austenite Temperature

UPPER BAINITE (High Temperature) LOWER BAINITE (Low Temperature) Carbon supersaturated plate Carbon diffusion into austenite Carbon diffusion into austenite and carbide precipitation in ferrite Carbide precipitation from austenite

0.2 µm

with carbides

1 µm

Carbide-free alloys wt %

Very poor toughness!

50 µm

T-zero curves

50 µm

0.4C-3Mn-2Si 0.4C-4Ni -2Si 0.2C-3Mn-2Si Impact Energy Test temperature / °C

Pearlite Martensite Bainite kilocycles to Crack Initiation Yates, Jerath

Advances in carbide-free bainitic steels Ultimate tensile strength / MPa Fracture toughness / MPa √m 18 wt% Ni maraging steel QT

an apple weighs 1 Newton 1 m = 1 Pa

Scifer, 5.5 GPa with ductility! Kobe Steel

Atom probe image of Scifer, 5.5 GPa steel wire Bhadeshia and Harada, 1993

1 Denier: weight in grams, of 9 km of fibre 10 Denier Scifer is 9 Denier

200 °C for 20 days 2.5 GPa Caballero, Mateo & Bhadeshia

Advances in carbide-free bainitic steels Ultimate tensile strength / MPa Fracture toughness / MPa √m 18 wt% Ni maraging steel QT

Bundy (1965)