Ni- and Be-free Zr-based bulk metallic glasses with high glass-forming ability and unusual plasticity

We developed Ni- and Be-free Zr45+xCu40−xAl7Pd5Nb3 bulk metallic glasses with large glass-forming ability and unusual plasticity. The alloys have large critical diameters (larger than 10 mm) in a wide composition range (x=0–20). The Zr50Cu35Al7Pd5Nb3 and Zr55Cu30Al7Pd5Nb3 alloys exhibit the largest critical diameter (between 18 and 20 mm). The Zr45+xCu40−xAl7Pd5Nb3 bulk metallic glasses also have large plastic elongation in wide composition range (x=10–17). The Zr62Cu23Al7Pd5Nb3 bulk metallic glass exhibits significant plasticity (over 20% of plastic elongation). With increasing Zr content, the compressive strength decreases except for the Zr67Cu18Al7Pd5Nb3 alloy. The fragility parameters were calculated to evaluate the glass-forming ability and plasticity. The fragility exhibits more sensitive correlation with plasticity than glass-forming ability. The ZrCuAlPdNb bulk metallic glasses have high crystallization activation energies of above 300 kJ/mol. The ZrCuAlPdNb bulk metallic glasses are favorable for application to biomaterials.