| With the advantages of high thermal conductivity,low expansion coefficient and low density,diamond/Al composites can well meet the demand for heat dissipation in electronic packages and is expected to solve the problem of chip heat dissipation.However,the current research on diamond/Al composites cannot meet the demand for large-scale industrial production of diamond/Al composites.In addition,due to the extremely high hardness of diamond,there are difficulties in cutting and processing of diamond/Al composites,which affects the wide application of this material to a certain extent.Therefore,it is crucial to study the preparation process,thermal properties and cutting performance of diamond/Al composites.In this paper,we use squeeze casting method as the preparation method to study the prefabricated block preparation process and aluminum infiltration process in the production of diamond/Al composites,and investigate the thermal and cutting properties of the prepared diamond/Al composites products.The main research contents are as follows:1.The maximum volume fraction of diamond in the prefabricated blocks is determined according to the accumulation state of different grain size diamond,and the problem of small grain size diamond accumulation easy to agglomerate is solved.According to the block formation and the residual quality of thermal degreasing,polyvinyl alcohol(PVA)aqueous solution is selected as the binder for the preparation of prefabricated blocks.The preparation process of the prefabricated blocks is optimized to solve the problem of block formation and sticking to the mold.By analyzing the thermal degreasing process of the prefabricated blocks,the optimal temperature rise rate during the thermal degreasing process is determined.2.By investigating the variation of hydrogen content at different molten aluminum temperatures,the temperature range of molten aluminum is determined and the aluminum refining process is completed.The cause of defects after aluminum solidification is analyzed and the corresponding process optimization is carried out.The effects of preheating temperature,aluminum liquid temperature and infiltration pressure on the thermal conductivity of aluminumbased diamond are investigated through preparation experiments,and suitable preparation process parameters are selected.The immersion experiments are carried out using a large depth immersion mold to investigate the immersion effect at different immersion depths and to ensure the high density of the prepared diamond/Al composites.3.The variation patterns of thermal conductivity and thermal expansion coefficient of diamond/Al composites with diamond grain size and volume fraction are revealed by finite element simulations.The experimental measurement results are compared with the finite element simulation results to ensure the accuracy of the simulation results.Temperature impact experiments are conducted on the diamond/Al composites to study the changes of thermal conductivity of diamond/Al composites before and after the temperature impact experiments.4.Milling and EDM wire cutting are used for cutting and machining of diamond/Al composites to analyze the feasibility of cutting and machining of diamond/Al composites with different grain sizes.Polycrystalline diamond(PCD)milling cutters are used for milling smallgrained diamond/Al composites,and the variation of tool wear with milling time is studied under specific cutting parameters to determine the tool life.A structure of three-layer diamond/Al composite is proposed,which can ensure good thermal properties of the material while providing certain cutting performance of the surface layer.The above research can solve the problems related to the production and preparation of diamond/Al composites,provide an effective way to improve the thermal and cutting properties of diamond/Al composites,and provide theoretical and technical support for the large-scale industrial production and practical application of diamond/Al composites. |
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