Size and Interface Coherency Dependent Phase Transformation of Niobium Nanoparticles Embedded in Copper Matrix by Mechanical Alloying

Abstract

The object of this work is to investigate the interface and size effects on the structural phase transition of Nb nanoparticles (NPs) embedded in Cu matrix. By means of X-ray diffraction analysis and high-resolution transmission electron microscopy observation, it is found that higher coherency of the Cu/Nb interface benefits the occurrence of phase transition in Nb NPs with larger sizes. The sufficient conditions for the transition are: (1) the size of Nb NPs should be smaller than 8 nm; (2) the Cu/Nb interfaces should be semi-coherent or coherent. The experimental results are consistent with the predictions of Bond Energy model.