Influence of Y and Nb addition on Crystallization Behavior and Mechanical Properties of Zr-Ni-Al-Cu-M Bulk Amorphous Alloys

摘要

Bulk amorphous alloys are new class of materials with excellent mechanical and thermal properties. Bulk metallic glasses (BMGs) have wide range of application such as structural materials. Minor alloying additions play beneficial role in the production and properties of BMGs. The present study was conducted to investigate the effect of Y and Nb addition on activation energy, crystallization behavior, thermal and mechanical properties of Zr_(64.5)Ni_(15.5)Al_(11.5)Cu_(8.5). Bulk amorphous ingots and sheets of three [Zr_(0.645)Ni_(0.155)Al_(0.115)Cu_(0.085)]_(100-x)M_2 (M = Y and Nb and x = 0, 2 at.%) alloys were produced by Cu mold casting technique. The alloys were characterized by XRD, DSC, SEM, FESEM and EDS. Activation energies were calculated. The alloy containing Y shows single stage crystallization while Nb addition shows double stage crystallization. The maximum activation energy calculated is 300 kJ/mol. Parameters describing thermal stability in these systems were determined from DSC data which improved as a result of these additives. Reduced glass transition temperature T_(rg) and thermal parameters like γ, δ and β were improved by Y addition. The supercooled liquid region varies between 87-100 K. Hardness and elastic moduli were also improved. It was concluded that Y and Nb addition has beneficial effect on mechanical properties. Three phases NiZr_2 and CuZr_2 and Cu_(10)Zr_7 were identified by XRD and confirmed by EDS in the samples annealed at 823 K while the AlNiY ternary phase was detected in the alloy containing Y.