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

Abstract

We developed Ni- and Be-free Zr(45+x)Cu(40-x)Al₇Pd₅Nb₃ 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 Zr(45+x)Cu(40-x)Al₇Pd₅Nb₃ 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.