Microstructure Evolution and its Modelling of Spray Deposited Al Matrix Composite Sheet during Wedge Pressing

Abstract

Spray deposited SiCP/Al-Fe-V-Si composite is characterized with pores and oxide films between deposited particles, therefore further densification is needed. Densification of the composite preforms in large size has becomes the research emphasis and challenge. Current research of the composite is focused on densification technologies used to eliminate metallurgical defects. Key parameters of wedge pressing, density and stress distribution, flow behaviour, densification mechanism and regularity are investigated by combining experiment and finite element modelling. Pass reduction of 10%~15% and space of about 10mm between one end of the plate blank and the steel mould is beneficial to wedge pressing because of the effective deformation. Density and stress of the external layer are higher than that of the inter layer, density and stress distribution become uniform with overall reduction. Materials in preformed area flows along thickness direction as thickness of the plate decreases, while materials in main deformation area flows along length direction with increasing length of the plate. Wedge pressing of the spray deposited Al matrix composite plate follows porous metal plastic deformation mechanism under the condition of plane strain. Practical relative density of the plate is higher than the calculated value in the initial stage of pressing, while the practical relative density becomes lower than the calculated value as true strain exceeds 0.55, which can be attributed to the pores resulted from aggregation and breaking of SiC particles.