Analysis of the Regulatory Effect of Semi-Solid Isothermal Treatment Time on Crystallization and Plasticity of Amorphous Composites

Ti48Zr27Cu6Nb5Be14 amorphous composites were prepared by copper mold suction casting to obtain as-cast specimens. Subsequently, the as-cast specimens were held at 900 °C for different durations (5, 10, 20, 30, and 40 min) and then water quenched to cool, yielding treated specimens. Room-temperature compression tests were conducted to characterize the mechanical properties of the materials before and after the treatment. X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM) were used to detect and observe the microstructure of the specimens (before and after treatment) as well as the morphology of the side surface of compressed fractured specimens. Results show that the as-cast specimens are amorphous matrix composites, with dendrites (identified as β-Ti) predominantly distributed in the amorphous matrix. When the treatment duration increased from 5 to 40 min, two key phenomena were observed. The dendrites gradually disappeared and evolved into curved crystals first; subsequently, the curved crystals transformed into elongated crystals. Finally, the elongated crystals evolved into short and thick rod-like crystals, which further transformed into near-spherical crystals or spherical crystals. Furthermore, as the treatment duration prolonged, the average equivalent size of the crystals increased continuously, reaching 23.1 μm. Additionally, the plasticity of the specimens first increased, reached a maximum value of 16.2% when held for 30 min, and then decreased.