A Ti–Zr–Be–Fe–Cu bulk metallic glass with superior glass-forming ability and high specific strength

• The glass-forming ability of Ti41Zr25Be28Fe6 glassy alloy can be dramatically enhanced by Cu alloying.
• ϕ32 mm (Ti41Zr25Be28Fe6)91Cu9 fully glassy rod has been prepared by copper mold tilt-pour casting.
• It is the largest Ti-based BMGs reported up to date.
• This BMG also possesses a high specific strength of 3.7 × 105 N m kg−1.
• The specific strength is the highest among those of BMGs with critical size larger than 30 mm.

It has been found that alloying with Cu element could significantly enhance the glass-forming ability (GFA) of Ti–Zr–Be–Fe alloy. As a result, a series of centimeter-scale (Ti41Zr25Be28Fe6)100−xCux (x = 0–20 at.%) bulk metallic glasses (BMGs) have been developed. Especially for those with x = 7–13 at.% Cu content, the critical size is larger than 20 mm. Among these Ti-based BMGs, (Ti41Zr25Be28Fe6)91Cu9 (also noted as Ti37.31Zr22.75Be25.48Fe5.46Cu9) glassy alloy exhibits superior GFA with a critical size larger than 32 mm, which is the largest size of Ti-based BMGs ever reported so far. The enhancement of the GFA is suggested to arise from the Cu addition-induced decrease in both the liquidus temperature and the Gibbs energy difference between the undercooled liquid and the crystalline phases of Ti–Zr–Be–Fe alloy. In addition to its superior GFA, the lightweight (Ti41Zr25Be28Fe6)91Cu9 alloy also exhibits a remarkable high specific strength of 3.7 × 105 N m kg−1 and an apparent plastic strain of 1.2%.