不同粒径TiB2/Cu复合材料热传导模拟与实验

采用ANSYS对不同粒径TiB₂/Cu复合材料热传导过程进行模拟。采用粉末冶金法制备了不同粒径TiB₂增强的Cu复合材料，采用LINSEIS LFA1600激光导热仪测试了室温至280℃下的TiB₂/Cu复合材料热传导性能变化，并与模拟结果进行对比。结果表明:热导率模拟结果与实验结果吻合较好。在50~200℃之间，复合材料热导率变化不大，在6%~9%范围内波动。200℃之后，模拟值与实验值均呈现出随温度升高而增大的趋势，且吻合度较高。这是由于温度低于200℃时，在模拟过程中未考虑材料界面处两相不同热膨胀系数的影响，导致模拟值与实验值有较大的差异。当温度高于200℃时，模拟值和实验值吻合程度趋于稳定。在200℃时，由于两相热膨胀系数的影响，复合材料内部界面处等效应力大于Cu基体屈服强度，使其发生塑性变形，从而引起热导率发生较大幅度变化。此外，热导率随着TiB₂粒径的增大呈现出先提高后降低的趋势，在10 μm时达到最大。这是由于当颗粒直径小于临界平均直径时，颗粒直径的增大会减少界面数量，从而降低界面热阻。当颗粒直径大于临界平均直径时，平均自由程l的急剧增加导致热导率降低。 

Thermal conduction simulation and verification of TiB2/Cu composites with different particle sizes

ANSYS was used to simulate the thermal conduction process of TiB₂/Cu composites with different TiB₂ particle sizes. The TiB₂/Cu composites with different TiB₂ particle sizes were prepared by powder metallurgy. LINSEIS LFA1600 laser thermal conductivity instrument was used to determine the thermal conductivity of the TiB₂/Cu composites ranging from room temperature to 280℃, and the measured values were compared with the simulation results. The simulation results are in good agreement with the measured values. In the range of 50-200℃, the thermal conductivities of the TiB₂/Cu composites fluctuate in the range of 6%-9%. When the temperature is above 200℃, both the simulated results and the measured values increase with the increase of temperature, and they match well with each other. This is because the large difference of their thermal expansion coefficients in the interface between TiB₂ and Cu below 200℃ is not considered in the simulation process. When the temperature is above 200℃, the simulation results have good accordance with the measured values. At 200℃, due to the influence of two-phase thermal expansion coefficients, the equivalent stress at the internal interface of the composite is larger than the yield strength of the Cu matrix, thus causing plastic deformation, which leads to a significant change in the thermal conductivity. In addition, the thermal conductivity increases and then decreases with the increase of particle size, and reaches its maximum value at 10 μm. This is because when the particle diameter is less than the critical average diameter, the increased particle diameter reduces the number of interfaces, thus reducing the interfacial thermal resistance. When the particle diameter is larger than the critical mean diameter, the mean free path l greatly increases and the thermal conductivity reduces.