Microstructure and Thermal Conductivity of the As-Cast and Annealed Al–Cu–Mg–Si Alloys in the Temperature Range from $25\,^{\circ }\hbox {C}$ to $400\,^{\circ }\hbox {C}$

Abstract

Four Al-based Al–Cu–Mg–Si alloy ingots were prepared by electrical resistance furnace. Microstructures and phase identification of the alloys were investigated by using electron probe microanalysis and X-ray diffraction techniques, respectively. The temperature dependences of thermal diffusivity and thermal conductivity of the as-cast and annealed alloys were investigated within the temperature range from $25\,^{\circ }\hbox {C}$ to $400\,^{\circ }\hbox {C}$, and the estimated thermal conductivity was correlated with the microstructure and (Al) matrix phase compositions of the alloys. According to the results, the thermal conductivity of Al–Cu–Mg–Si alloys increased with temperature. The formation of precipitates, which consumes solute elements in the (Al) phase, contributes to the improvement in thermal diffusivity and thermal conductivity of annealed Al–Cu–Mg–Si alloys. The complex interconnection precipitates with a lower thermal conductivity than (Al) phase may affect the continuity of the matrix phase in microstructure and decreasing the thermal conductivity of the alloys significantly.