Effects of the size and matrix microstructure on compression of borosilicate spheres - Zn22Al2Cu composites with foam behaviour.

Abstract

Borosilicate spheres - Zn22Al2Cu composites with a 2.9 g/cm³ density were prepared to assess whether changes in size affect the compression behaviour and whether this effect depends on the alloy matrix microstructure. The composite material was manufactured first by alloy melting, then by sphere submersion into the liquid alloy and finally by air-cooling the resulting mixture to room temperature. The matrix microstructures used separately were as-cast microstructure and fine microstructure. They were characterised by optical and scanning electron microscopies as well as by an energy dispersive X-ray spectroscopy (EDS) compositional analysis of polished and etched samples. The compression was tested in three samples of each size at a 1 mm/min crosshead speed. The compression curves of composites with fine microstructure in matrix are similar in shape to those of ideal metallic foams, whereas curves of the composites having as-cast microstructure in matrix have a shape like compression curves of Zn and Al₂O₃ foams. The as-cast microstructure is more susceptible to changes in size than is the fine microstructure. Thus, the foam compression behaviour of borosilicate spheres - Zn22Al2Cu composites changes with the increase in size, and this change depends on the matrix microstructure.