Microstructural evolution and tensile properties of an in-situ TiZr-based bulk metallic glass matrix composite after hot-pressing deformation in its supercooled liquid region

Abstract

Hot-pressing deformation treatment was carried out at different strain rates and temperatures to improve the microstructure homogeneity of the TiZr-based bulk metallic glass matrix composites (BMGMCs) after enlargement. At a compression strain rate of 0.001/s and temperature of 653 K, the TiZr-based BMGMCs exhibited good plastic rheological properties in supercooled liquid region. After work hardening to the peak stress, steady-state flow stress was rapidly obtained, resulting in a stress drop of 223 MPa. Moreover, during this period, no rapid stress drop and fracture phenomena were observed. Compared with those of the as-cast morphology, the distribution of dendrite and glass matrix was more homogeneous after 31% thickness reduction in hot-pressing deformation. Accompanied with viscous flow of the glass matrix, the dendrites markedly aggregated together after a thickness reduction ratio of 58%. Transmission electron microscopy analysis revealed that a large amount of dislocations formed in the dendrite, and a large amount of nanocrystals precipitated from the glass matrix after hot-pressing treatment. The amount of the nanoparticles continued to increase as the amount of deformation increased. TiZr-based BMGMCs with 31% compression deformation possessed both the distinguished plastic strain (εp) of 3.95% and ultimate strength (σmax) of 1595 MPa. The stress–strain curve demonstrated that the rate of stress drop considerably slowed down after tensile strength reached a maximum due to hot-pressing deformation. The rapid expansion of the shear band was efficiently hindered through the combined effect of partial nanocrystallization of the glass matrix and deformation hardening of the dendrite. This condition further improves the total coordinated deformation capacity of TiZr-based BMGMCs.