spinodalkäyrä

A spinodalkäyrä, meaning "spinodal curve" in Finnish, is a concept used in thermodynamics and materials science. It describes a boundary in a phase diagram separating a stable phase from a region where the phase is metastable. Beyond the spinodalkäyrä, a homogeneous phase is unstable and will spontaneously decompose into two or more phases. This decomposition occurs through a process known as spinodal decomposition, which is a nucleation-free mechanism.

The spinodalkäyrä is distinct from the binodal curve, which represents the boundary between a stable single phase and a region of metastability where phase separation occurs via nucleation and growth. Within the spinodal region, small fluctuations in composition are amplified, leading to the formation of interpenetrating, interconnected domains of the new phases. This process results in a characteristic fine-grained microstructure.

The location of the spinodalkäyrä depends on factors such as temperature, pressure, and composition. It is often determined experimentally or through theoretical modeling of the free energy landscape of the system. Understanding the spinodalkäyrä is crucial for controlling the microstructure and properties of materials, particularly in alloys, polymers, and glasses, as it dictates the pathways for phase transformations.