Crystallization of Zr55Al10Ni5CU30 bulk metallic glass composites containing ZrC particles

Zr55Al10Ni5CU30 bulk metallic glass composite containing 10 vol% crystalline ZrC particles was prepared by an in-situ reaction between Zr-based melt and graphite powder being followed by an injection casting into a copper mould. The crystallization process of the composites during annealing at 723 K has been investigated by using DSC, TEM and microhardness test. It is found that an unknown crystalline phase appears first along the interface between ZrC particle and the matrix of the composite, and then a homogeneous nanocrystallization occurs in the matrix. The nanocrystalline phase precipitated in the matrix is determined to have orthorhombic structure by using TEM diffraction. It has a higher hardness than the hardness of the amorphous phase which remained in the matrix. Hardness of the matrix increases with increasing the volume fraction of the nanocrystalline phases. After annealed at 723 K for 40 min. most of the matrix has been transformed into crystalline phases with a final average grain size of about 120 nm.