Non-contact measurements of thermophysical properties of titanium at high temperature

Abstract

Four thermophysical properties of both solid and liquid titanium measured using the high-temperature electrostatic levitator at JPL are presented. These properties are density, thermal expansion coefficient, constant pressure heat capacity, and hemispherical total emissivity. For the first time, we report the density, the thermal expansion coefficient, and the ratio of the constant pressure heat capacity to the hemispherical total emissivity of undercooled titanium over a wide range of temperatures. Over the 1650 K to 2000 K temperature span, the liquid density can be expressed asρ (T)/(kg · m−3)= 4.208 · 103− 0.508 · (T−Tm)/K withTm= 1943 K, and the corresponding volume expansion coefficient asα= 1.169 · 10−4K−1. Similarly, over the 1540 K to 1940 K temperature range, the measured density of the solid can be expressed asρ (T)/(kg · m−3)= 4.321 · 103− 0.212 · (T−Tm)/K, giving a volume expansion coefficient α= 4.76 · 10−5K−1. The constant pressure heat capacity of the liquid phase could be estimated as Cp, m(T)/(J · K−1· mol−1)= 45.5 − 3.21 · 10−3· (T−Tm)/K if the hemispherical total emissivity of the liquid phase ϵTremains constant at 0.34 over the 1650 K to 2000 K temperature range. Over the 1540 K to 1940 K temperature span, the hemispherical total emissivity of the solid phase could be rendered asϵT (T) = 0.297 + 5.952 · 10−5· (T−Tm)/K. The enthalpy of fusion has also been calculated as 14.3 kJ · mol−1.