For a full explanation of what ductility is and why it matters as a physical property of aluminium, see our dedicated guide: Why ductility is an important physical property of aluminium.
Why aluminium's crystal structure keeps it ductile and tough in the cold
Aluminium is known to sustain or even improve both ductility and toughness at very low temperatures. This is due to negligible yield-strength temperature sensitivity of the face-centered cubic (FCC) crystal structure of aluminium.
FCC aluminium does not show the ductile-to-brittle transition of body-centered cubic (BCC) materials, in which the dislocations Peierls stress can rise to such high levels at low temperatures that brittle fracture intervenes.
Young's modulus of aluminium at cryogenic temperature
Young's modulus, the measure of aluminium's stiffness, typically increases slightly as temperature decreases toward cryogenic levels. This happens because interatomic bonding forces strengthen marginally as thermal vibration in the lattice decreases, making the material modestly stiffer, not more brittle, in the cold. Combined with aluminium's FCC crystal structure, this is part of why aluminium components retain predictable structural behavior in low-temperature environments rather than becoming unpredictable or prone to sudden failure, the pattern that makes BCC metals like carbon steel risky in the same conditions.
Aluminium safe for offshore installations
Aluminium is therefore considered a safe material for offshore installations – especially when the oil and gas industry is moving north.
Other factors that favor aluminium in cold climates are low weight, no surface treatment necessary and low maintenance costs.
One challenge related to the use of aluminium alloys in the oil and gas industry is related to controlling the mechanical strength of joints, particularly the strength of weldments. Recent results confirmed, for example, that there is no reduction in strength at low temperatures for welded thick plates as compared with thin plates.
