To fabricate electronic packaging shell of coppermatrix composite with characteristics of high ther mal conductivity and low thermal expansion coefficient, semisolid forming technology, and powder metallurgy was combined. Conventional mechanical mixing of Cu and SiC could have insufficient wettability, and a new method of semisolid processing was introduced for billets preparation. The SiC/Cu composites were first prepared by PM, and then, semisolid reheating was performed for the successive semisolid forging. Composite billets with SiC 35 % vol ume fraction were compacted and sintered pressurelessly, microstructure analysis showed that the composites pre pared by PM had high density, and the combination between SiC particles and Cualloy was good. Semisolid reheating was the crucial factor in determining the micro structure and thixotropic property of the billet. An opti mised reheating strategy was proposed： temperature 1,025 ℃and holding time 5 min.
The unsteady, laminar, incompressible, and two-dimensional flow of a mi- cropolar fluid between two orthogonally moving porous coaxial disks is considered. The extension of von Karman＇s similarity transformations is used to reduce the governing partial differential equations （PDEs） to a set of non-linear coupled ordinary differential equations （ODEs） in the dimensionless form. The analytical solutions are obtained by employing the homotopy analysis method （HAM）. The effects of various physical param- eters such as the expansion ratio and the permeability Reynolds number on the velocity fields are discussed in detail.
