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Thermal interface material (TIM) that exists in a liquid state at the service temperature enables efficient heat transfer across two adjacent surfaces in electronic applications. In this work, the thermal conductivities of different phase regions in the Ga-In system at various compositions and temperatures are measured for the first time. A modified comparative cut bar technique is used for the measurement of the thermal conductivities of GaxIn1−x (x = 0, 0.1, 0.214, 0.3, and 0.9) alloys at 40, 60, 80, and 100 °C, the temperatures commonly encountered in consumer electronics. The thermal conductivity of liquid and semi-liquid (liquid + β) Ga-In alloys are higher than most of the TIM’s currently used in consumer electronics. These measured quantities, along with the available experimental data from literature, served as input for the thermal conductivity parameter optimization using the CALPHAD (calculation of phase diagrams) method for pure elements, solution phase, and two-phase region. A set of self-consistent parameters for the description of the thermal conductivity of the Ga-In system is obtained. There is good agreement between the measured and calculated thermal conductivities for all of the phases. Due to their ease of manufacturing and high thermal conductivity, liquid/semi-liquid Ga-In alloys have significant potential for TIM in consumer electronics. 

Abstract Transitioning current cooling and refrigeration technologies to solid-state cooling leveraging the magnetocaloric effect would improve efficiency and eliminate a harmful influence on the environment. Employing additive manufacturing as a production method would increase geometrical freedom and allow designed channels and porosity in heat exchangers made from magnetocaloric materials, to increase surface area for heat transfer via a fluid. This study is the first to demonstrate a successful deposition of the Ni43Co7Mn39Sn11 magnetocaloric material by direct laser deposition. Samples were defined as either properly- or overbuilt, and representative ones were characterized for microstructural features before and after homogenization heat treatment, as well as magnetic behavior and constituent phases. As-built microstructures consisted of dendrites, columnar grains, and elongated cells, with a mix of both austenite and 7M martensite phases. Homogenization increased the fraction of 7M martensite, and encouraged distinct equiaxed and columnar grains, eliminating dendrites and cellular structures. The increased fraction of the weak magnetic martensitic phase also resulted in a strong reduction of the saturation magnetization. Some differences in structure and performance may be related to an energy density difference causing higher Mn loss in the properly built sample, with a lower powder-to-energy input ratio. As a whole, it is found that direct laser deposition (DLD) additive manufacturing of Ni-Mn-based magnetocaloric material is very promising, since representative transformation, phase state, and magnetic properties have been achieved in this study.