Fabrication of Two-Layered Al-B{sub}4C Composites by Conventional Hot Pressing Under Nitrogen Atmosphere and Their Characterization

摘要

In this study, we describe the conventional hot pressing (CHP) of layered Al-B{sub}4C composites and their characterization. The matrix alloy Al-5 wt.%Cu was prepared from elemental powder mixtures, The metal and B{sub}4C powders were mixed to produce either Al-Cu-10vol.%B{sub}4C or Al-Cu-30vol.%B{sub}4C combinations. Then, these powder mixtures were stacked as layers in the hot pressing die to form a two-layered composite. Hot pressing was carried out under nitrogen atmosphere to produce 30×40×5 mm specimens. Microstructural features and age hardening characteristics of composites were determined by specimens cut longitudinally. The flexural strength of both layered composites and their monolithic counterparts were investigated via three point bending tests. In the case of layered specimens of both 10vol.%B{sub}4C and 30vol.%B{sub}4C containing layers were loaded for three-point test. The results show that a homogeneous distribution of B{sub}4C particles in the matrix alloy which is free of pores, can be obtained by CHP method. The ageing behavior of the composites was found to be influenced by the reinforced materials, i.e. higher hardness values were reached in 8 hrs for the composites than that for the matrix alloy. Flexural strength test showed that two-layered composites exhibited improved damage tolerance depending on layer arrangement. Microstructural investigation of the fracture surfaces of the bending specimens was performed by means of scanning electron microscope (SEM). While layer with lower reinforcement content exhibited large plastic deformation under loading, the other with higher reinforcement content exhibited less plastic deformation.