Glass forming ability and a novel method for evaluating the thermoplastic formability of ZrxTi65-xBe27.5Cu7.5 alloys. (November 2019) - Song, Xinxiang
Abstract: Zr-Ti-based bulk metallic glass (BMG), in particular Be-Cu-bearing BMG (Vitreloy), displays an outstanding combination of characteristics, i.e. while showing good glass forming ability (GFA) it exhibits low glass transition temperature ( T g ) and a relatively wide supercooled liquid region (SCLR, Δ T ), facilitating their thermoplastic formability, which is critical for BMG applications. In the present work, the effect of composition on the GFA and thermoplastic formability in Zr x Ti65- x Be27.5 Cu7.5 BMG alloys are investigated in the range x = 20, 25, 30, 35, 40, 45, 50 at%. Results show that GFA is optimal in the composition range from 30 to 45 Zr at%. In addition, the optimal composition range for thermoplastic formability is consistent with that for GFA. Furthermore, 3-mm diameter BMG rods with the aspect ratio 2:1 are compressed in the SCLR at temperatures T = 643 K and T = T g + Δ T /2, by applying a constant load of 8 kN, and the thermoplastic formability is evaluated measuring the final diameters d 1 and d g-Δ T, respectively. The larger measured d g-Δ T values in the optimal composition range indicates that the ideal temperature for the thermoplastic formability is given by T = T g + Δ T /2. Graphical abstract: Image 1 Highlights: A series of good glass formers has been developed. Effect of composition on glass forming ability and thermoplastic formability have been investigated via theoretically thermodynamic calculation. A newly determined formability characterization method has been proposed. The optimal composition range for excellent glass forming ability coincides with that for high thermoplastic formability.