Modeling the amorphous forming ability of Ti-based alloys with wide supercooled liquid regions and high hardness

Ti-based bulk metallic glasses presented here are designed in a multi-dimensional composition space using a series of modeling tools. A chemical short range order model was used to evaluate the bonding behavior between the constituent species. This technique predicts the local structure present in the amorphous phase. A structural model is then used to further optimize the composition space, ensuring an efficient topology within the amorphous phase. These two models are compared with the predicted liquidus profile. Deep eutectics correlate well with glass forming ability, and their location and depth are located and quantified using a searching technique over a broad compositional range. Ti-based alloys were designed according to these three models, and the alloys with the highest glass forming ability represent a balance between having a densely packed cluster structure and a close proximity to a deep eutectic. Bulk metallic glass compositions have been successfully produced over a wide compositional space with only cost-effective alloying elements, Ni, Cu, Si, and Sn, using these models. The best glass former in this composition space, Ti48Ni32Cu8Si8Sn4, demonstrates a supercooled liquid region in excess of 100 K, and was successfully cast into fully amorphous rods, 3 mm in diameter, with a compressive fracture strength of ∼1.8 GPa.