Embrittlement
Embrittlement is used to describe any phenomena where the environment compromises a stressed material's mechanical performance, such as temperature or environmental composition.
Various materials have different mechanisms of embrittlement, therefore it can manifest in a variety of ways, from slow crack growth to a reduction of tensile ductility and toughness.
Yet this mechanism is much slower than that of liquid metal embrittlement (LME), suggesting that it directs a flow of atoms both towards and away from the crack.
One of the more conventional ways is to place coatings around the metal, which will act as diffusion barriers that prevents hydrogen from being introduced from the environment into the material.
Duplex stainless steel is widely used in industry because it possesses excellent oxidation resistance, but it can have limited toughness due to its large ferritic grain size and embrittlement tendencies at temperatures ranging from 280 to 500 °C, especially at 475 °C, where spinodal decomposition of the supersaturated solid ferrite solution into Fe-rich nanophase (
), accompanied by G-phase precipitation, occurs,[3][4][5] which makes the ferrite phase a preferential initiation site for micro-cracks.
[7] If the material is under creep (under low strain rate and high temperature condition), the voids will coalesce into vacancies which compromises the mechanical strength of the workpiece.
At low temperatures, some metals can undergo a ductile-brittle transition which makes the material brittle and could lead to catastrophic failure during operation.
However, only BCC and some HCP metals meets the third condition as they have high Peierl's barrier and strong energy of elastic interaction of dislocation and defects.
All FCC and most HCP metals have low Peierl's barrier and weak elastic interaction energy.
Historically, there are multiple instances where people are operating equipment at cold temperatures that led to unexpected, but also catastrophic, failure.
In Cleveland in 1944, a cylindrical steel tank containing liquefied natural gas ruptured because of its low ductility at the operating temperature.
[9] Another famous example was the unexpected fracture of 160 World War II liberty ships during winter months.
The most common sources of polymer embrittlement include oxygen in the air, water in liquid or vapor form, ultraviolet radiation from the sun, acids, and organic solvents.
An increase in the number of cross-links (due to an oxidative environment for example), results in stronger, less ductile material.
When silicone rubber is exposed to air at temperatures above 250 °C (482 °F) oxidative cross-linking reactions occur at methyl side groups along the main chain.
The solvent diffuses into the bulk, swells the polymer, induces crystallization, and ultimately produces interfaces between ordered and disordered regions.
