Powder Metallurgy Fabrication And Properties Of Sip/Al Functional Gradient Materials

The aluminum silicon composites have been concerned as a new kind of electronic packaging material, and widely used in aerospace and electronic technology, for its excellent comprehensive properties, such as low density, high thermal conductivity, low thermal expansion coefficient, good welding and machining. Recently, with the development of Sip/Al electronic packaging materials in aerospace applications, the researchers pay attention to the thermal expansion coefficient, thermal conductivity and strength of Sip/Al electronic packaging material, and neglect the air tightness, welding and machining. Based on the above problems, we put forward the fabrication of aluminum silicon functional gradient materials.By comparing different methods to fabricate functional gradient materials, we propose to prepare by using powder metallurgy hot pressing. Based on experiment design, the influence of hot pressing temperature, pressure and sintering temperature, time on the properties of FGM were studied, and the thermal conductivity and expansion coefficient of FGM with Al-Si single component composites by calculating with theoretical models and experimental measurement were compared. In addition, the ANSYS finite element analysis software was used to simulate the thermal conductivity and thermal stress of Al-Si FGM, the changes of thermal conductivity and thermal stress varied with different silicon content were studied. Results are drawn as follows:(1) After hot pressing(HP) and hot isostatic pressing(HIP), the material density of Sip/Al FGM is2.4～2.5g/cm3, the size of Si particles is fine, and the content of layers is well distribution. The properties of Sip/Al FGM after HIP show expansion coefficient(0～400℃) of11.7×10-6/K, the thermal conductivity of121W/m*K, bending strength of228Mpa, hardness of the layers of132、151and170HB.(2) With the increasing of sintering time and temperature, the grains of Al-Si FGM grow, and part of aluminum liquid losses, which will lead composition segregation, the density and various properties of Al-Si FGM decreasing, respectively.(3) By caculating with several theoretical models, we found that with the increasing of silicon content, the thermal conductivity and expansion coefficient of Al-Si composites become smaller. According to the comparison, the thermal conductivity and expansion coefficient of Al-Si five layers functional gradient materials (Al-40Si/Al-50Si/Al-65Si/Al-50Si/Al-40Si) are similar to Al-50Si.(4) The thermal conductivity of Sip/Al composites was calculated by theoretical model. The multi-particle random distribution and three layers and five layers random distribution FGM models of Al-Si composites in plane were established by ANS YS finite element method. The effect of factors such as Si particle volume fraction, matrix metal on thermal conductivity of Sip/Al composites were investigated. The results show that theoretical model calculation result is consistent with the results of finite element analysis and the thermal conductivity of Sip/Al composites dropped with the increase of Si particle volume fraction. The thermal conductivity of Al matrix compound material is higher than Al-12Si matrix, and the thermal conductivity of Al-Si FGM is slightly lower than ANSYS finite element analysis.(5) Choosing A1-50Si、Al-Si three layers FGM (Al-40Si/Al-50Si/Al-65Si/Al-50Si/Al-40Si) and Al-Si five layers FGM (Al-40Si/Al-50Si/Al-65Si/Al-50Si/Al-40Si) as the analysis objects, simulating and comparing the temperature and thermal stress distribution in the working environment. Compared with Al-Si three layers FGM, the thermal stress of Al-Si five layers FGM is weakened, the corresponding deformation becomes smaller.