Indentation and deformation behavior of FeCo-based bulk metallic glass alloys

FeCo-based bulk metallic glass with the compositions (Fe0.5Co0.5)69−xNb6B25+x (x=0, 2, 4) were cast using electric arc melting and suction casting technique. The samples were tested and analyzed in as-cast, sub-Tg annealed and partially crystalline conditions. Vicker's microhardness was found to increase after annealing and partial crystallization. For high boron content hardness values approaching 1400 HV were obtained in partially crystalline samples. A compressive strength value of 4776 MPa was calculated using hardness data. Sub-Tg annealing resulted in a decrease in the size of deformation zone formed underneath the hardness indenter after indentation. The bulk metallic glass alloys were embrittled by the partial crystallization treatment. It resulted in the formation of corner cracks during indentation. The size of the deformation zone increased with an increase in load. Semicircular and radial type of shear bands were observed as in the deformation zone with a higher number of radial shear bands observed in the annealed samples compared to as-cast samples. A comparison is made between the size of the deformation zone obtained experimentally and that predicted by the available models.