Nanoindentation deformation behavior of pulse laser welded Zr-based bulk metallic glasses after crystallization

In the experiment, pulse laser beam was used to join Zr-based bulk metallic glasses with aluminum to study nanoindentation deformation behavior of bulk metallic glasses after crystallization in welded joints. In this paper, influence of different crystallized phase content on deformation behavior was analyzed in detail from the perspective of free volume and plastic deformation energy dissipation. Micro-area X-ray diffraction studies of different zones in weld joints indicated that three different crystallinity regions were formed due to different cooling rate. Weld consisted of partial crystalline zone (fusion zone and heat affected zone) and amorphous zone (BMGs base metal), and hard intermetallic compounds such as Zr₂Cu and Zr₂Ni were formed. Serrated flow behavior and pile-up morphologies around indentation were discussed in this paper. It was verified that regions with more free volume in bulk metallic glasses exhibited more obvious serrations during nanoindentation. Fusion zone with the highest crystalline fraction showed the highest nanoindentation hardness and reduced contact modulus. In the indentation load range of 1 600 ～ 3 100 μN, plastic deformation energy dissipation in nanoindentation increased with indentation load.