Metastable–Stable

Most metallic materials are often cast. This is a highly dynamic process where composition and solidification conditions can become a challenge due to the appearance of porosity, shrinkholes, segregations, and the formation of intermetallic phases. Heat treatments are applied to get rid of segregations, stable, and metastable intermetallic phases for homogenization purposes and to obtain a material that is homogeneous with an adjustable property profile. However, often it is observed that the dissolution especially of metastable phases really takes long times (hundreds or even thousands of hours) and high temperature which is accepted in the academic world but not acceptable for real industrial applications due to time and costs. Especially for biodegradable metals, metastable phases perhaps could be regarded as “stable” when the time of absorption is in range of a few weeks only and could be used to adjust properties.