Formation of two-glassy-phase bulk metallic glass in Zr-Co-Al-Y immiscible system

Liquid phase separation phenomenon presents a unique opportunity to design two-glassy-phase bulk metallic glass (BMG). In this work, two-glassy-phase Zr56-xCo28Al16Yx (x = 15, 20, 28 and 36 at.%) BMGs were prepared by using injection-casting method. The analyses of microstructure and thermal properties suggest that all the Zr-Co-Al-Y BMGs have a typical liquid phase separation induced two-glassy-phase (ZrCo-rich and Y-rich glassy phase) microstructure. Further results confirm that these two-glassy-phase microstructures include droplet-type (ZrCo-rich or Y-rich droplet) and interconnected-type microstructure. The microstructure differences in Zr-Co-Al-Y BMGs are depending on the Y content. The viscosities of Zr-Co-Al-Y BMGs in the supercooled liquid region show a wider temperature range compared with Zr56Co28Al16 BMG. Moreover, the formation mechanisms of the two-glassy-phase Zr-Co-Al-Y BMGs are investigated. [Display omitted] •Two-glassy-phase Zr-Co-Al-Y BMGs were successfully fabricated.•Zr-Co-Al-Y BMGs with different microstructures can be adjusted by controlling the Y content.•Y20 BMG shows a low viscosity (