Preparation of laminated Al/B4C composites with gradient structures and properties through centrifugal freezing and pressure infiltration.

Lightweight Al/B 4 C composites with a gradient lamellar structure were fabricated through centrifugal freezing and pressure infiltration. Their ceramic volume fraction showed a continuous increase from the central region to the surface region, the increase being from approximately 23 vol% to 44 vol%, and the spatial variation of their composition and microstructure led to a gradient change in their mechanical properties. The bending strength and hardness increased with the B 4 C content, and they attained the highest values of 424 ± 16 MPa and 130.6 ± 4.2 HV 0.3 at the surface region of the composite, respectively. By contrast, the work of fracture reached the maximum value (3763 ± 268 J/m2) at the central region of the composite because of the high metal content and the existence of multiple extrinsic toughening mechanisms. The proposed method is versatile and economical and is suitable for the preparation of composites with heterogeneous structures and gradient properties. [ABSTRACT FROM AUTHOR]