Embrittlement

Embrittlement is a significant decrease of ductility of a material, which makes the material brittle. Embrittlement is used to describe any phenomena where the environment compromises a stressed material's mechanical performance, such as temperature or environmental composition. This is oftentimes undesirable as brittle fracture occurs quicker and can much more easily propagate than ductile fracture, leading to complete failure of the equipment. 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. Embrittlement is a series complex mechanism that is not completely understood. The mechanisms can be driven by temperature, stresses, grain boundaries, or material composition. However, by studying the embrittlement process, preventative measures can be put in place to mitigate the effects. There are several ways to study the mechanisms. During metal embrittlement (ME), crack-growth rates can be measured. Computer simulations can also be used to enlighten the mechanisms behind embrittlement. This is helpful for understanding hydrogen embrittlement (HE), as the diffusion of hydrogen through materials can be modeled. The embrittler does not play a role in final fracture; it is mostly responsible for crack propagation. Cracks must first nucleate. Most embrittlement mechanisms can cause fracture transgranularly or intergranularly. For metal embrittlement, only certain combinations of metals, stresses, and temperatures are susceptible. This is contrasted to stress-corrosion cracking where virtually any metal can be susceptible given the correct environment. 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. For neutron embrittlement, the main mechanism is collisions within the material from the fission byproducts. Hydrogen embrittlement One of the most well discussed, and detrimental, embrittlement is hydrogen embrittlement in metals.