Deformational Behavior And Mechanisms Of Ti-based In-situ Metallic Glass Matrix Composites At Room Temperature

Amorphous alloys exhibit no obvious plasticity at room temperature due to local shearing upon loading. Aiming at improving plasticity, in situ dendrite-reinforced metallic glass matrix composites(MGMCs) are developed. Although the alloys display obvious plasticity, high strength and succinct preparation processes and so on, the softening behavior prevails after yielding at room temperature, which results in early failure. To resolve this problem, Ti48Zr18V12Cu5Be17 in-situ MGMCs are developed. The tensile behavior of dendrites is obtained experimentally combining nano-indentation measurements and finite-element-method analysis. Besides, the tensile behavior of the MGMCs is divided into four stages:(1)elastic-elastic,(2) elastic-plastic,(3) plastic-plastic(work-hardening), and(4) plastic-plastic(softening). The respective constitutive relationships at different deformation stages are quantified. The calculated results coincide well with the experimental results. As a result, the improved tension model can be applied to clarify and predict the tensile behavior of the MGMCs.According to the proposed tension model, it is found that Yong’s moduli has an impact on mechanical properties of MGMCs during tensile deformation. Thus, Ti48Zr18V12Cu5Be17in-situ MGMCs are cold rolled, which indicate that modulus and hardness of matrix is decreased with increasing in thickness reduction, while the modulus of dendrites remains constant, and hardness tends to increase sharply with the increase of the thickness reduction below 30 %, and then, it approximately remains constant. Free volumes created during plastic deformation lead to the decrease of the matrix’ modulus. Invariability in inter-atomic distanceleads to the modulus of dendrites unchanged upon loading.The tension model predicts that plasticity of in situ dendrite-reinforced MGMCs can be optimized when the Young’s modulus of the glass matrix matches that of dendrites. To prove that result, the tensile pre-deformation experiment is designed, which ensures that the Young’s modulus of the glass matrix matches that of dendrites. The study shows that the pre-deformation is utilized to exploit notable increases in plasticity, accompanied by slight increases in the compressive strength, and the deformation mechanisms are explored. The increased free volumes in the glass matrix after tensile pre-deformation contribute to the decreasing in Young’s modulus of the glass matrix and lead to the increase of the stress concentration, promoting multiplication of shear bands. Matching Young’s modulus opens a door to design in-situ MGMCs with excellent plasticity and remarkable work-hardening capability.