Deformation And Fracture Behavior Of Metallic Glasses And Their Composites

Bulk metallic glassy alloys have almost theoretical high strength, excellent wear properties, good forming ability and thermal stability in the supercooled liquid region. With the development of manufacturing techniques, high quality bulk samples with stable performances would be produced. This creates conditions for a further investigation on deformation and fracture behavior. In the mean time, such investigation may provide important theoretical guidance for structural and technological design of these materials, and theses materials were used in manufacture and people's living as structural materials finally. In this paper, the deformation and fracture behavior of a series of bulk amorphous alloys (bulk monolithic metallic glasses and metallic glassy composites with dendrites) were investigated. The experiments consisted of the dependence of Vicker hardness and compressive properties, the fragmentation fracture of bulk metallic glass materials, the effect of aspect ratio on the compressive deformation and fracture behavior of bulk metallic glass and the toughening mechanisms of Ti-based nanostructured composite containing ductile dendrites. The main results are as follows:(i) The dependence between Vicker hardness and compressive properties of the metallic glass composites containing dendrites with strong work hardening was not allowed the empirical relationship, ie HV/3≈σf, but other compressive properties, such as fracture strengthσf, yield strengthσy, Young's module E, Working-harden exponent n and the ratio between Elastic energy and Total energyδΕ/δΤalso play significant roles in determining the hardness. (ii) The Mg-based metallic glass displayed a special failure mode, ie fragmentation fracture. And the normal shear fracture can be regarded as one of the special failure modes among fragmentation fracture. (iii) The aspect ratio plays a more important role in the plasticity than the yield strength for metallic glassy materials. (iv) The metallic glass with dendrites displayed high strength, plasticity and strong work hardening ability. The high strength was attributed to the amorphous and nanostructure matrix. And the propagation of the shear bands was strongly resisted by the dendrites, leading to a high plasticity.