In Situ Synthesis and Characterization of Zr-Based Amorphous Composite By Laser Direct Deposition

Zr-based bulk metallic glasses have attracted extensive interest for structural applications due to their excellent glass forming ability, superior mechanical properties, unique thermal and corrosion properties. In this study, Zr₆₅Al₁₀Ni₁₀Cu₁₅ amorphous composites with a large fraction of amorphous phase were in-situ synthesized by laser direct deposition. X-ray diffraction confirmed the existence of both amorphous and crystalline phases. Laser parameters were optimized in order to increase the fraction of amorphous phase. Microstructure analyses by scanning electron microscopy revealed the deposited structure was composed of periodically repeated amorphous and crystalline phases. Overlapping regions with nanoparticles aggregated were crystallized by laser reheating and remelting processes during subsequent laser scans. Vickers microhardness of the amorphous region showed around 35% higher than that of the crystalline region. Average hardness obtained by Rockwell macrohardness tester was very close to the microhardness of the amorphous region. Differential scanning calorimetry test results further revealed the existence of amorphous phase and glass transition temperature T_g was observed to be around 655K. In 3 mol/L NaCl solution, laser direct deposited amorphous composites exhibited distinctly improved corrosion resistance, compared with fully-crystallized samples.