Fast heating and melting of alumina under the effect of concentrated laser radiation

The results are given of calculations of temperature fields in a plane layer of $\text{Al}_2\text{O}_3$ crystal under conditions of combined radiative-conductive energy transfer under fast heating by concentrated radiation of a $\text{CO}_2$ laser with the formation of a thin layer of melt on the surface. Experiments are performed in the heating of ceramic samples of $\text{Al}_2\text{O}_3$ and samples remelted from $\text{Al}_2\text{O}_3$ powder; in these samples, the intensities of outgoing radiation and the reflectivity are measured for different wavelengths. The experimental results are compared with the calculation results. It is demonstrated that the adopted mathematical model, which fails to reflect the important part played by kinetics in the abrupt variation of the absorption coefficient in $\text{Al}_2\text{O}_3$ melt, needs to be refined.