Mechanical properties of bulk metallic glass compositesWednesday (26.09.2018) 11:45 - 12:00 S1/01 - A1 Part of:
Even though bulk metallic glasses show many interesting properties as high strength and elasticity, the lack of an internal microstructure impedes the adjustment of properties. Therefore, instead of using single-phase materials, a promising composite approach is introduced in this work. Combinations of amorphous and crystalline phases or different amorphous phases are produced via high pressure torsion starting from powders. Severe plastic deformation techniques offer the possibility to adjust microstructural features of the composites by changing the powder ratio and the applied strain. Hence, structural dimensions can be modified in the range of tens of nanometers to tens of micrometers. The effects on mechanical properties are investigated by means of microhardness measurements, nanoindentation with different strain rates and also at elevated temperatures, and in-situ micro-pillar compression testing. The latter test revealed a strong dependence on the type, fraction, and orientation of the second phase. An increase in strength accompanied by brittle failure is observed in nano-lamellar structures, in which partial intermixing at interphase boundaries occurs. Higher ductility can be reached with thicker lamellae and a favorable orientation, moreover a hindered propagation of shear bands can be observed. Nanoindentation showed a strong influence of temperature and a change of deformation behavior near the glass transition temperature.