Modelling of changes in properties of alloys at elevated temperatures

Long-term exposures of heat-treated metals at sufficiently elevated temperatures (e.g. tempering of quenched steels or age-hardening of supersaturated solid solutions) cause substantial changes in their structures and, consequently, substantial changes in their physical and materials properties. These processes are different in principle but their temporal development as well as their temperature dependence can be modelled by similar types of equations. Their kinetics is generally described by the Johnson–Mehl–Avrami–Kolmogorov equation, the Arrhenius equation expresses their temperature dependence. The paper presents another way more deeply respecting the scheme of processes proceeding in studied materials, which leads to more precise description. The modelling is presented for two cases: for the tempering of quenched bearing steels and for the age-hardening of beryllium bronze.