Manufacturing of Cu-based metallic glasses matrix composites by spark plasma sintering

A preliminary study has shown that bulk metallic glasses of the CuZrAl type of large dimension may be manufactured from amorphous powders densified by a process of sintering such as spark plasma sintering (SPS). However, to remedy the lack of plasticity of these materials, the addition of ductile crystalline particles was carried out in the present study. The zirconium was chosen because its properties are close to those of the amorphous matrix. The same sintering parameters as those optimized for the metallic glass are also applicable for the production of the composite for the different zirconium volume fractions retained, respectively 5%, 10%, 20%, 30%, 40% and 50%. The materials obtained are dense. X-ray diffraction clearly indicates that only the amorphous matrix CuZrAl and the crystalline zirconium are present. Young's modulus as well as the elastic limit decrease only very slightly with the addition of crystalline particles. Decrease in hardness is more pronounced. On the other hand, the plastic deformation increases with the addition of zirconium, reaching about 4.9% for the alloy containing 50% zirconium. The analysis of the fracture surfaces clearly shows the role of the ductile crystalline particles, namely the deceleration of the shear bands. The influence of volume fraction and size of the crystalline particles and of matrix toughness is discussed from a mechanical point of view. Therefore, SPS is a solution to solve both the problem of size and low ductility of amorphous metal, since it is possible to control microstructure and so to control mechanical properties.