A bridge from metallic glasses to medium-entropy alloys in Ti-Cu-Zr-Pd-Co system: Design, microstructure, and deformation-induced-martensitic transformation

Since single solid solution tends to form in medium- or high-entropy alloys (MEAs or HEAs), it offers an opportunity to obtain shape-memory type bulk metallic glass (BMG) composites when the selected system belongs to not only BMG but also MEAs or HEAs. Herein, through phase prediction parameters used in MEAs and HEAs, the phase formations for the medium-entropy Ti₄₀Cu_36-xZr₁₀Pd₁₄Co_x (x = 2, 4, and 6 at.%) glass-forming alloys were evaluated before experiments. According to prediction, both fully amorphous samples and BMG composites were fabricated by rapid solidification. To observe the phase formations and the transformation-induced-plasticity (TRIP) effect, fully crystalline MEAs were obtained by annealing. With increasing Co addition, B2 Ti(Pd,Cu) phase can be stabilized to room temperature. All the samples exhibit excellent mechanical properties mainly due to different contributions from the transformation strengthening, second phase strengthening, and dislocations strengthening effects.