Compositional Dependence of Thermal Conductivity of Molten Cu-Fe Alloy at Low Fe Contents
- PDF / 708,654 Bytes
- 6 Pages / 593.972 x 792 pts Page_size
- 74 Downloads / 150 Views
he liquid–liquid phase separation in alloys, which have a metastable miscibility gap in the undercooled state, is a well-known phenomenon.[1] Cu-based alloys, such as Cu-Fe and Cu-Co alloys, are typical immiscible alloys; thus, they have been used as a model material to investigate the liquid–liquid phase separation phenomena. Furthermore, Cu-based alloys gain much attention because solidified alloys with phase separation structures express novel properties depending on the structures.[2–5] The phase separation phenomena and the resultant solidified structures are affected by some operational factors during undercooling and solidification (e.g., cooling rate,[6–8] degree of undercooling,[9–16] and melt convection[17–23]). The heat and mass transfer mechanism in the molten alloys during undercooling must be clarified to develop and optimize processes (e.g., welding and casting) producing new alloys with novel properties determined by phase separation structures. Therefore, the thermophysical properties of molten alloys in the undercooled state are indispensable.
EITA SHOJI, NAOTO ITO, MASAKI KUBO, and TAKAO TSUKADA are with the Department of Chemical Engineering, Tohoku University, 6-6-07, Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan. Contact e-mail: [email protected]. HIROYUKI FUKUYAMA is with the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University Sendai, Miyagi 980-8577, Japan. Manuscript submitted June 18, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS B
A containerless technique is desired for measuring the thermophysical properties of molten metals and alloys because measurements are difficult to perform due to the high reactivity of molten samples. One solution for this problem is the electromagnetic levitation (EML) technique. The normal spectral emissivity of molten Cu,[24] Fe,[25,26] Co,[27] Cu-Co alloy,[28] and Cu–Fe alloy[29] is measured by utilizing the EML technique. Even excluding measurements by the EML, the emissivity of such molten metals and alloys has been extensively investigated.[30–38] In contrast, the measured data on the thermal conductivity of molten Cu, Fe, Co, and their alloys are scarce[39–42] compared with emissivity because the thermal conductivity measurements are strongly affected by melt convection in the molten sample (e.g., Marangoni convection caused by a non-uniform temperature distribution on the surface and magnetohydrodynamic (MHD) convection caused by the Lorentz force in the EML technique). Thus, the suppression of melt convection has become a key technique for the precise measurement of the thermal conductivity. The author’s research group proposed and developed an electromagnetic levitator superimposed with a static magnetic field to measure the thermophysical properties of various molten metals and alloys. First, the EML can realize a containerless process to avoid contamination from the container wall and heterogeneous nucleation on the wall. Second, the technique enables the measurement of the thermal conductivity of molten mate
Data Loading...
