High-Temperature Pyrometric Measurement of Thermal Diffusivity by a Flash Method: $\mathrm{Co}$–$\mathrm{Si}$ and $\mathrm{Co}$–$\mathrm{Ge}$ Systems

The paper deals with an automated system for measuring the thermal diffusivity of metals and alloys by a flash method involving the use of a contactless technique of recording the superheat temperature of a specimen. The solution of the heat equation for a cylinder with due regard for the Gaussian distribution of energy over the laser beam cross section forms the basis of the measurement method. The structural scheme of the experimental facility is described using an IBM PC and a GOR-100M type laser. The results of measuring the thermal diffusivity of $\mathrm{Co}$–$\mathrm{Si}$ and $\mathrm{Co}$–$\mathrm{Ge}$ systems in the temperature range of $300$–$1650$ K are presented. The polytherms of the thermal diffusivity in the vicinity of the Curie point and in $\epsilon \to \alpha$ structural transitions exhibit anomalies. These anomalies are smoothed out as the concentrations of $\mathrm{Si}$ and $\mathrm{Ge}$ increase, and are not observed at a concentration of admixtures higher than $10$ at. $\%$. The obtained results are in satisfactory agreement with the diagrams of state for $\mathrm{Co}$–$\mathrm{Si}$ and $\mathrm{Co}$–$\mathrm{Ge}$ alloys.