Fabrication of two-layered Al-B4C composites by conventional hot pressing uuder nitrogen atmosphere and their characterization


Bedir F.

JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY, cilt.20, ss.1002-1011, 2006 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 20 Konu: 7
  • Basım Tarihi: 2006
  • Doi Numarası: 10.1007/bf02915999
  • Dergi Adı: JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY
  • Sayfa Sayıları: ss.1002-1011

Özet

In this study, we describe the conventional hot pressing (CHP) of layered Al-B4C composites and their characterization. The matrix alloy Al-5 wt.%Cu was prepared from elemental powder mixtures. The metal and B4C powders were mixed to produce either Al-Cu-10vol.%B4C or Al-Cu-30vol.%B4C 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 X 40 X 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.%B4C and 30vol.%B4C containing layers were loaded for three-point test. The results show that a homogeneous distribution of B4C 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.