Mechanical behavior and deformation mechanism of shape memory bulk metallic glass composites synthesized by powder metallurgy

Abstract

• Powder metallurgy synthesis of bulk metallic glass composites with TRIP effect. • Quantification of confining effect of glassy phase on martensitic transformation. • Quantification of each phase to the plasticity of bulk metallic glass composites. • Mechanism for shear band initiation in shape memory bulk metallic glass composites. The synthesis of martensitic or shape-memory bulk metallic glass composites (BMGCs) via solidification of the glass-forming melts requires the meticulous selection of the chemical composition and the proper choice of the processing parameters in order to ensure that the glassy matrix coexists with the desired amount of austenitic phase. Unfortunately, a relatively limited number of such systems, where austenite and glassy matrix coexist over a wide range of compositions, is available. Here, we study the effectiveness of powder metallurgy as an alternative to solidification for the synthesis of shape memory BMGCs. Zr 48 Cu 36 Al 8 Ag 8 matrix composites with different volume fractions of Ni 50.6 Ti 49.4 are fabricated using hot pressing and their microstructure, mechanical properties and deformation mechanism are investigated employing experiments and simulations. The results demonstrate that shape-memory BMGCs with tunable microstructures and properties can be synthesized by hot pressing. The phase stability of the glass and austenitic components across a wide range of compositions allows us to examine fundamental aspects in the field of shape memory BMGCs, including the effect of the confining stress on the martensitic transformation exerted by the glassy matrix, the contribution of each phase to the plasticity and the mechanism responsible for shear band formation. The present method gives a virtually infinite choice among the possible combinations of glassy matrices and shape memory phases, expanding the range of accessible shape memory BMGCs to systems where the glassy and austenitic phases do not form simultaneously using the solidification route.