The effect of the addition of Ta on the structure, crystallization and mechanical properties of Zr-Cu-Ni-Al-Ta bulk metallic glasses

Zr-based bulk metallic glasses (BMGs) or bulk metallic glass matrix composites (BMGCs) have been prepared by using a copper-mold casting in the Zr65−xTaxCu17.5Al7.5Ni10 (where x = 1-10 at%) alloy system while varying the Ta content. A monolithic amorphous phase of BMG was achieved when Ta was less than 2 at%, while amorphous matrix composites reinforced by Ta-solid solutions were obtained when Ta is 5 at% or higher. The addition of Ta also affected significantly the crystallization of the amorphous phase. A multi-step process of crystallization with a preferential formation of quasicrystals occurred in the alloys containing 2-5 at% Ta, while a single-step pathway of crystallization with the formation of stable Zr-Cu intermetallic compounds took place when Ta was beyond this range. In addition, a quasi-static compression test revealed that both fracture strength and plasticity of the base BMG were remarkably enhanced as Ta content increased. The effect of the addition of Ta on the structure; crystallization process; and deformation behavior of the Zr-based alloys is discussed.