Haurausmuutos

Haurausmuutos, often translated as brittleness transition or ductile-brittle transition, is a phenomenon observed in certain materials, particularly metals, where their behavior under stress changes significantly with temperature. Below a specific temperature, known as the transition temperature, the material tends to fracture in a brittle manner, meaning it breaks suddenly with little or no plastic deformation. Above this temperature, the material exhibits ductile behavior, undergoing significant plastic deformation before fracturing.

This transition is crucial in engineering design, especially for structures that operate at varying temperatures. For instance, the choice of steel for ships, pipelines, or bridges must consider the lowest expected operating temperature to avoid brittle fracture, which can lead to catastrophic failure. Factors influencing the transition temperature include the material's composition, microstructure, and the presence of defects. Alloying elements and heat treatments can be used to lower the transition temperature, making the material more ductile at lower temperatures.

The underlying mechanism involves changes in the material's deformation and fracture modes. At low temperatures, crack propagation is easier due to limited atomic mobility and dislocation movement, favoring brittle fracture. As temperature increases, atomic vibrations become more energetic, facilitating dislocation slip and allowing for more plastic deformation before fracture, leading to ductile behavior. Understanding and controlling haurausmuutos is therefore essential for ensuring the safety and reliability of structures and components.