AlSiC

Abstract: The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of AlMgSi alloys and AlSiC metal matrix composites. In Part I the different components of the model are outlined and analytical solutions presented which provide quantitative information about the HAZ temperature distribution for a wide range of operational conditions. Moreover, a general procedure for modelling the HAZ strain rate distribution has been developed by introducing a series of kinematically admissible velocity equations which describe the material flow fields in the radial, the rotational, and the axial direction, respectively. Calculations performed for both types of materials show that the effective strain rate may exceed 1000 s −1 in positions close to the contact section due to the high rotational velocities involved. Application of the model for evaluation of the response of AlMgSi alloys and AlSiC metal matrix composites to the imposed heating and plastic deformation is described in an accompanying paper (Part II).

Abstract: The effects of SiC reinforcement and matrix aging treatment on fatigue crack growth behavior in a powder metallurgy aluminum 2124 alloy-SiC whisker composite were investigated. The microstructures were designed such that the matrix of the composite material and the unreinforced control aluminum alloy 2124 with an identical processing history had similar hardness and precipitation characteristics. The threshold stress intensity factor range ΔK0 for tensile fatigue crack growth was obtained using a procedure whereby mode I precracks were initiated in uniaxial cyclic compression prior to tension fatigue. The composite exhibits a ΔK0 value which is about twice that of the control alloy. However, ΔK0 is relatively insensitive to variations in both the aging treatment and the mean stress of the fatigue cycle in both the composite and the control alloy. Possible mechanisms underlying this trend are discussed.

Abstract: Tensile tests with superimposed hydrostatic pressures were performed on two types of metal matrix composite: 2014 Al with 20% SiC particles and 2124 Al with 14% SiC whiskers. In the materials with SiC particulate, the ductility increases rapidly with pressure and the mode of damage initiation is by particle fracture. Materials containing SiC whiskers exhibit a different fracture mode involving whisker matrix decohesion, and strain localization which results in shear fracture.

Abstract: A ceramic circuit board with a heat sink which has a long life under heat cycles. First and second aluminum plates are laminated and bonded onto both sides of a ceramic substrate through Al--Si-based brazing solders, respectively. A heat sink formed of an AlSiC-based composite material is laminated and bonded onto a surface of the first aluminum plate. The ceramic substrate is formed of AlN, Si 3 N 4 or Al 2 O 3 . An Al alloy in the heat sink has an Al purity of 80-99% by weight, and the first or second aluminum plate has an Al purity not less than 99.98% by weight. The heat sink is laminated and bonded onto the first aluminum plate through the Al alloy in the heat sink.