Mechanical behavior of metallic glasses and metallic glass matrix composites

Quasistatic and dynamic compression tests on Zr/Hf based bulk metallic glasses revealed decreasing fracture strength with increasing strain rate and decreasing Hf content. It is believed that dynamic loading promotes crack nucleation immediately following shear band initiation whereas quasistatic loading promotes shear bands to grow to maturity.; Quasistatic and dynamic compression tests were conducted on four tungsten preform reinforced Vit105 (Zr52.5Ti5Cu 17.9Ni14.6Al10) and Vit106 (Zr57Nb 5Cu15.4Ni12.6Al10) metallic glass composites. All the composites exhibited large plastic strain under both quasistatic and dynamic compression. In general, the dynamic loading resulted in higher failure stress than the quasistatic loading. The deformation behavior was found to be dominated by the ductile W phase. Microscopic observation of the deformed and fractured specimens revealed shear banding in the glassy phase, cracking along the particle boundaries and severe deformation of W particles. It is also found that the processing methods have strong influence on the mechanical behavior of the composites even when they have the same matrix and the same volume fractions of the reinforcement.; Micromechanics models are developed for tungsten (W)-based bulk metallic glass (BMG) matrix composites employing the Voronoi tessellation technique and the finite element (FE) method. The simulation results indicate that the computed elastic moduli are close to those measured in the experiments. The predicted stress-strain curves agree well with their experimentally obtained counterparts in the early stage of the plastic deformation. An increase in the W volume fraction leads to a decrease in the yield stress and an increase in the Young's modulus of the composite. In addition, contours of plastic strain for increasing applied strains provide an explanation why shear bands were observed in the glassy phase, along the W/BMG interface, and in the W phase of failed WBMG composite specimens.