Transformation-mediated plasticity in CuZr based metallic glass composites: A quantitative mechanistic understanding

Abstract

In this paper, we present a thorough stress analysis of the Cu-Zr metallic-glass composite with embedded B2 particles subject to a martensitic transformation. Within the framework of the Eshelby theory, we are able to explain, in a quantitative manner, (1) the formation of three types of shear bands with distinct morphologies as observed experimentally in the severely deformed Cu-Zr metallic-glass composite and (2) the work hardening ability of the Cu-Zr metallic-glass composite as related to the coupled effects of elastic back stress and elastic mismatch caused by the martensitic transformation. Furthermore, we also discuss the issues about the stress affected zone of the individual B2 phase and the stability of the crystalline-amorphous interface. Given the general agreement between the theoretical and experimental findings, we believe that the outcome of our current work can lead to a deeper understanding of the transformation-induced plasticity in the Cu-Zr based metallic glass composites, which should be very useful to the design of the metallic-glass composites with improved ductility.

In-situ tensile testing of ZrCu-based metallic glass composites

“…5(e and f) . Considering the stress field around one inclusion 30 , the distribution of stress field is believed to coincide with the distribution of the multiple shear bands, as shown in Fig. 2(d) .…”

“…The precipitation of the B2 phase can influence the stress field that improves the density of shear bands, and optimizes the chemical composition to achieve more stabilized the phase formation of B2 28 . The metastable B2 phase can effectively promote the formation of multiple shear bands, and improve the plastic deformation capability of BMGCs, which is attributed to the complicated stress states of glassy matrix and the secondary phase 17 , 25 , 29 , 30 . In addition, various microstructural factors, such as volume fraction, length scale, and yield strength of the secondary phases, have a great influence on the strain delocalization 31 .…”

Transformation-induced plasticity in bulk metallic glass composites evidenced by in-situ neutron diffraction

“…The difference in the volume fraction leads to the variation of yielding stress while that in the distribution profile may cause the fluctuation of yielding stress around the ROM line. Both of them affect local stress field [28] and thus influence the martensitic transformation upon loading, which will be addressed in detail later on.…”

Applicability of the interface spring model for micromechanical analyses with interfacial imperfections to predict the modified exterior Eshelby tensor and effective modulus

“…The non-uniform strain field at a position 𝒙 in the matrix can be expressed with a similar form as 𝜺 𝒙 𝑺 , 𝒙 : 𝜺 * , where the superscript "Ext" refers to the exterior, and 𝑺 , 𝒙 is the exterior Eshelby tensor 12,13 . The exterior Eshelby tensor and the exterior strain concentration tensor, 𝑨 , 𝒙 , have been used to consider the shear localization of metallic glass, the matrix failure point for reinforced composites, and the interaction among the reinforcements [14][15][16] .…”

“…The non-uniform strain field at a position in the matrix can be expressed with a similar form as , : * , where the superscript "Ext" refers to the exterior, and , is the exterior Eshelby tensor 12, 13 . The exterior Eshelby tensor and the exterior strain concentration tensor, , , have been used to consider the shear localization of metallic glass, the matrix failure point for reinforced composites, and the interaction among the reinforcements [14][15][16] .Further progress on the inclusion or inhomogeneity problem has been achieved by considering the interfacial damage present in realistic composites where debonding or slip between the matrix and inclusion can occur. As a simplified model of interfacial imperfection, J. Qu introduced a linear-spring layer of vanishing thickness at the interface to represent the displacement jump between the inclusion and the matrix 17, 18 .…”