Embrittlement

Embrittlement is a process by which a material that is ordinarily ductile becomes brittle, losing plasticity and toughness and fracturing under stresses it would normally withstand. It can arise from environmental exposure, impurities, and changes to temperature or irradiation, and it often leads to premature or unpredictable failure.

Common forms include hydrogen embrittlement, temper embrittlement, environmental embrittlement, irradiation embrittlement, and sulfide stress cracking. Hydrogen embrittlement occurs when hydrogen diffuses into a metal and reduces cohesive strength or promotes crack initiation; it is particularly problematic for high-strength steels and some aluminum alloys, often triggered by corrosion, hydrogen charging, or processing steps such as electroplating. Temper embrittlement is temperature dependent; at intermediate temperatures, elements such as phosphorus, tin, antimony, or arsenic segregate to grain boundaries and weaken intergranular cohesion, lowering toughness. Irradiation embrittlement arises in materials exposed to high-energy neutrons or ions, creating defect clusters that hinder dislocation motion and reduce toughness. Sulfide stress cracking is a hydrogen-assisted phenomenon in sour oil and gas environments, where sulfide ions promote crack growth under load.

Mechanisms are debated; key ideas include hydrogen-enhanced decohesion and hydrogen-assisted localized plasticity, along with grain boundary segregation and irradiation-induced damage. Embrittlement is typically evaluated by fracture-toughness tests such as K_IC or J_IC, and impact tests like Charpy.

Prevention strategies include avoiding exposure to embrittling agents, using alloys with lower susceptibility, heat treatments to reduce impurity segregation, protective coatings, reducing residual stresses, and controlling environmental conditions.