Glass formation in Cu50Zr50-xAlx and (Cu50Zr43Al7)100-xNbx alloys

In the present work, the effects of Al and Nb elements on the formation of glassy phase in Cu-Zr based bulk metallic glasses (BMGs) have been investigated. In this regards, different Cu50Zr50-xAlx and (Cu50Zr43Al7)100-xNbx samples with 2 mm in diameter were prepared using arc melting followed by injection casting in water-cooled copper mold. The results illustrated that Al has positive effect on increasing the glass forming ability (GFA) of Cu-Zr system, and it is possible to create a completely glassy structure in Cu50Zr43Al7 sample. In contrast, the addition of Nb has destructive effects on glass forming ability, the homogeneity and final mechanical properties of Cu-Zr-Al BMGs. The segregation of Nb during solidification process and precipitation of brittle B2-CuZr and Cu10Zr7 phases are the main reasons of lower ductility and compressive strength in the presence of Nb element. As-solidified samples containing Nb showed compressive fracture strength in the range of 1000-1650 MPa, which was much lower than Nb-free alloy (2050 MPa).