Weldability and corrosion resistance of OF Cu47Ti34Zr11Ni8 metallic glass

Vitreloy 101 (Cu47Ti34Zr11Ni8) metallic glass ribbons were investigated for compositional changes and crystallization induced by resistance spot welding. Strong welds were produced by completely melting the regions of metallic glass between the welder electrodes. Mechanical testing of the lap welds determined the shear strength to be 572±27 MPa, approximately half the shear strength of the native alloy. Minor crystallization was observed by differential scanning calorimetry (DSC), but was below X-ray diffraction (XRD) detectable levels. Embrittlement due to crystallization around the weld likely contributed to weld failure. While surface analysis with X-ray photoelectron spectroscopy (XPS) showed approximately 10% Cu enrichment in the weld affected regions, scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS) analysis showed no significant changes in bulk composition between the melted and native alloys. A computational model has been developed using finite elemental analysis (FEA) to understand heat transfer and quenching at the weld. The FEA model data is in good agreement with the XPS, SEM and differential scanning calorimetry data. In addition, the corrosion behavior of native and spot-welded Vitreloy 101 was investigated in NaCl and HCl solutions. The corrosion rates were calculated using both electrochemical and immersion methods, and were in good agreement. The metallic glass shows good resistance to NaCl solutions due to the spontaneous formation of TiO2 passivation layer, as confirmed by XPS analysis. The alloy performed slightly poorer in HCl solutions as a result of acid induced breakdown of the passivation layer. SEM imaging showed the glass samples to be susceptible to localized pitting corrosion, where selective dealloying of Ti and Zr was observed. The corrosion resistance of the welded samples was slightly lower than the native alloy due to the prevalence of stress corrosion cracking.