Liquid-Metal Embrittlement (LME)
Definition
Brittle fracture of a normally ductile metal when it is in contact with a specific liquid metal. Not hydrogen-related but mechanistically analogous: adsorption of a foreign species reduces grain-boundary cohesion.
- Requirement
- Ductile metal in contact with a specific liquid metal
- Mechanism
- Adsorption reduces grain-boundary cohesion
- Related concept
- Mechanistically similar to hydrogen embrittlement
Common questions
How can investigators distinguish LME from hydrogen embrittlement at a fracture site?+
LME requires physical contact with a specific liquid metal at the time of cracking, often leaving trace deposits of that metal at the fracture surface, whereas hydrogen embrittlement leaves no such metallic residue.
Why is LME described as mechanistically similar to hydrogen embrittlement?+
Both involve a foreign species adsorbing at grain boundaries and weakening the bonds between grains, causing brittle failure in a metal that would otherwise fail in a ductile manner.
Related terms
- Hydrogen-Assisted Cracking (HAC)
- The general term for crack initiation and propagation facilitated by absorbed atomic hydrogen. Encompasses hydrogen embrittlement, sulfide stress cracking, and hydrogen-induced cracking.
- Hydrogen Embrittlement (HE)
- Loss of toughness and ductility in a metal due to absorbed atomic hydrogen, resulting in brittle fracture at stress intensities below the...
- Hydrogen-Induced Cracking (HIC)
- Planar crack arrays that form parallel to the steel rolling direction when high levels of hydrogen are absorbed. Common in pipeline steels...
- NACE MR0175/ISO 15156
- The international standard for materials selection and qualification for sour oil-and-gas service. Sets hardness limits, alloy restrictions, and testing requirements to prevent...
- Sulfide Stress Cracking (SSC)
- Hydrogen-assisted cracking specific to H2S-containing environments. Sulfide ions poison the recombination reaction at the steel surface, forcing more atomic hydrogen to enter...