Amorphous-CuTa/amorphous-CoZrNb multilayers: Structure, mechanical properties and thermal stability

CuTa/CoZrNb multilayers were prepared by direct current magnetron sputtering. The structure, mechanical properties and thermal stability were investigated by X-ray diffraction, high-resolution transmission electron microscopy, vacuum annealing and nanoindentation. The results show that the as-deposited multilayers possess amorphous/amorphous structure. The amorphous feature leads to the lack of hardness enhancement with decreasing modulation periodicity, which can be attributed to the absence of the dislocation movement. After thermal annealing, the density increases due to the decrease of the bond distance and the annihilation of defects with increasing annealing temperature. The densification results in the enhancement of the elastic modulus and hardness. The enhancement for the multilayers with smaller modulation periodicity is more sensitive to thermal annealing because of larger volume fraction of interfaces.