Thermal Diffusivity of Iron at High Temperature in Both the Liquid and Solid States

Thermal diffusivity measurements of pure iron have been made using a laser flash apparatus (LFA) over the temperature range 25 to 1 640°C. These measurements are compared with existing data and recommended values are given. In the γ-Fe phase region the thermal diffusivity can be represented by a=6×10-6+3.13×10-9×(T–911). In the δ-Fe phase region the thermal diffusivity can be represented by the constant 0.07×10-4m2s-1. In the liquid region up to 1 640°C, the thermal diffusivity can be represented by a=6.2×10-6+1.79×10-9×(T–1538). T in both equations is temperature in Celsius and the thermal diffusivity equation units are m2s-1. To improve the LFA measurement characteristics of a metal, it is often coated with graphite. Unfortunately, due to the solubility of carbon in iron, at high temperatures, the coating does not remain on the surface of the iron. The effect of using a zirconia coating as opposed to a graphite coating was tested. The efficacy of this change was evaluated by comparing thermal diffusivity measurements on Cu using both coating materials.