Abstract

Functionally graded materials (FGM) containing different amounts of B4C particles within 4 layers in an aluminum matrix were produced and characterized. The layers contained B4C particles at amounts of 0, 5, 15 and 25 volume %. In order to form the composite structure, pure aluminum (<10 microns), copper (1 micron) and B4C powders (<10 microns) were utilized. After mixing, functionally graded materials were compacted and shaped in a rectangular cross sectional geometry, having 6.4 mm thickness, 12 mm width and 33 mm length, by cold pressing at 600 MPa pressure. The parts were pressureless sintered at 610 oC for 30 min in high purity nitrogen atmosphere. The properties of the FGM sample were compared with those of the sample which did not contain B4C particles, and which contained 25% B4C particles throughout the whole sample.
Microstructural examinations were performed by an optical microscope. 3- point bending tests were conducted by a universal testing machine. The sample that did not contain B4C particles presented a 3-point bending strength of 380 MPa, whereas the sample that contained 25 % B4C had a bending strength of 140 MPa. The FGM sample had a bending strength of 190 MPa. However, the failure of the FGM sample was composed of steps. The stepwise failure of the FGM sample was due to delamination and fracture of the layers containing 15 and 25 % B4C. Microhardness values of each layer the samples were determined by Vickers micro hardness measurements.