| The working distance and performance of the phased array radar are often proportional to the power of the T/R components,and the high power T/R components will cause heat loss and thermal mismatch issues accordingly.In this paper,high thermal conductivity,low expansion Al N is used as the reinforcement phase,and pure Al is used as the matrix.The volume fraction of AlNp/Al composites prepared by SPS method is 5%~55%,and the microstructure and thermophysical properties of the composites are analyzed by advanced analysis methods.The mechanical properties were systematically studied and the related influencing factors were analyzed.Based on this,three kinds of AlNp/Al layered gradient composites were prepared.The MSC.Marc finite element simulation software was used to analyze the AlNp/Al layered gradient composites.The temperature,stress and displacement of the package of the T/R module are changed;the surface of the AlNp/Al composite material and 6061 Al are modified by magnetron sputtering to deposit a thin metal layer;the AlNp surface modified by Sn Ag Cu solder is used.The Al alloy was connected to 6061 Al and the joint morphology and the formation and evolution of the interface structure were analyzed.By systematically studying the ball milling process(rotation speed,time)and SPS process(sintering temperature,holding time),AlNp/Al composites with high densification and low porosity were obtained.The volume fraction of 5% to 45% AlNp/Al composites prepared was dense and the Al N particles were uniformly distributed in the Al matrix.No obvious defects were found.The transmission structure observed that the Al N-Al interface is clean and clear,there is no interface reactant,and the interface is enriched with a layer of Al2O3 with a thickness of 5 nm to 6 nm.It is speculated that the surface of Al powder is introduced by oxidation during ball milling.The thermal conductivity,thermal expansion coefficient and plasticity of AlNp/Al composites decrease with the increase of Al N content.In a certain range,the tensile strength and bending strength of AlNp/Al composites increase with the increase of Al N particles content..The thermal conductivity of 45 vol.%AlNp/Al is 112W/(m·K),the thermal expansion coefficient is 13.52×10-6K-1,the tensile strength is 217 MPa,and the bending strength is 440.7MPa,compared to the pure Al test of SPS sintering.Samples were increased by 64.4% and 41.5%,respectively.According to the structure and properties of AlNp/Al composites,three kinds of AlNp/Al layered gradient composites were designed and prepared: two layers of pure Al-45 vol.%AlNp/Al,three layers of 5vol.%-25 vol.%-45 vol.% AlNp/Al,six-layer pure Al-5vol.%-15 vol.%-25 vol.%-35 vol.%-45 vol.% AlNp/Al layered gradient composite.The three kinds of AlNp/Al layered gradient composites have a dense structure,and the interfaces between layers are clear and distinct,with no obvious defects or voids.Using MSC.Marc finite element analysis software,three gradient materials and 6061 Al were used to calculate and analyze the T/R module package.The maximum value of Mises stress of gradient material was almost reduced by half compared with 6061 Al,indicating that the gradient material can mitigate heat loss.The thermal stress caused by the distribution is good.In order to improve the wettability of SnAgCu solder on AlNp/Al composites and 6061 Al surface,the surface modification was carried out by magnetron sputtering deposition of a thin layer of metallic Ni.The typical microstructures and interface structures of joints at 250°C after deposition of Ni monolayer metal and Ti/Ni bilayer metal on the surface of the base metal were investigated.The microstructure and interface structure evolution of joints at different holding times were investigated.The joints under two different process parameters were tested for shear strength and the fracture morphology and fracture mechanism were analyzed. |
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