Mechanism and influence of pulse-impact on the properties of liquid-phase pulse-impact diffusion welded SiC_p/A356

An investigation was conducted to study: (1) the mechanism of liquid-phase pulse-impact diffusion welding (LPPIDW); and (2) the influence of pulse-impact on the microstructure and tensile strength of LPPIDW-welded joints of the aluminum matrix composite (AMC) SiC_p/A356. The results showed that, during LPPIDW: (1) the interface state between the SiC particles and matrix was prominently affected by the pulse-impact; (2) the initial pernicious contact-state of reinforcement particles was changed from reinforcement (SiC)/reinforcement (SiC) to reinforcement (SiC)/matrix/reinforcement (SiC); (3) the harmful microstructure/brittle phase of Al₄C₃ was restrained from the welded joint; (4) the density of dislocation in the matrix neighboring to and away from the interface in the matrix was higher than its parent composite; and (5) the intensively mutual entwisting of dislocation was taking place. Studies illustrated that: (1) deformation mainly occurred in the matrix grain; and (2) in the deformation of rapid thermal pressing, the matrices around SiC particles engendered intensive aberration and offered a high-density nucleus area for matrix crystals, which was in favor of forming nano-grains and improved the properties of the successfully welded composite joints. Such distinctly welded composite joints gave: (1) a tensile strength of up to 179 MPa, which was about 74.6% of the stir-cast SiC_p/A356; and (2) a corresponding radial deformation of below 3%, which conformed well to the deformation specification of the welded specimens. © 2008 Springer-Verlag London Limited.