A strategy for designing Ti-based in-situbulk metallic glass composites with tailored structural metastability using conventional titanium alloys

The metastability of the dendritic phase is crucial in determining the mechanical properties and mechanisms of the Ti-based in-situdendrite-reinforced bulk metallic glass composites (BMGCs). However, tailoring the metastability effectively remains challenging. In this study, we propose a straightforward and effective strategy to tailor the dendrites composition and metastability using conventional Titanium alloys. Initially, six common Titanium alloys with increasing content of β-stabilizing elements such as Ti, Ti–6Al–4V, Ti–13Nb–13Zr, Ti–15Mo, Ti–12Mo–6Zr–2Fe and Ti-4.5Fe-6.8Mo-1.5Al were selected. Subsequently, a series of in-situdendrite-reinforced BMGCs denoted as T1-T6 were designed by alloying these Titanium alloys with a specific amorphous alloy. It was found that the microstructure, stability and mechanical behaviors of these composites change significantly as the content of β-stabilizing elements in the dendritic phase increases monotonically. Based on their microstructure and mechanical behaviors, these composites can be classified into three categories: T1, T2 and T3, T4-T6. The T1 alloy exhibits brittle deformation characteristics due to the significantly higher elastic modulus of the dendritic phase. In contrast, the T2 and T3 alloys demonstrate good tensile plasticity and remarkable work-hardening ability, attributed to the metastable β phase undergoing stress-induced phase transformation during deformation. On the other hand, the T4-T6 alloys, consisting of stable β phase, deform via dislocation slip, resulting in a higher yielding stress and compression plasticity. The composition design strategy presented in this study, along with the correlation between mechanical behaviors and dendrite stability, may offer a novel perspective for the development of Ti-based in-situdendrite-reinforced BMGCs.