Structure–Property Relationships in Shape Memory Metallic Glass Composites

Abstract

Metallic glass composites with shape memory crystals show enhanced plasticity and work-hardening capability. We investigate the influence of various critical structural aspects such as, the density of crystalline precipitates, their distribution and size, and the structural features and intrinsic properties of the phase on the deformation behavior of metallic amorphous Cu 64 Zr 36 composites with B2 CuZr inclusions using molecular dynamics simulations. We find that a low density of small B2 inclusions with spacing smaller than the critical shear band length controls the formation and distribution of plastic zones in the composite and hinders the formation of critical shear bands. When the free path for shearing allows the formation of mature shear bands a high volume fraction of large B2 precipitates is necessary to stabilize the shear flow and avoid runaway instability. Additionally, we also investigate the deformation mechanism of composites with pure copper crystals for comparison, in order to understand the superior mechanical properties of metallic glass composites with shape memory crystals in more detail. The complex and competing mechanisms of deformation occurring in shape memory metallic glass composites allow this class of materials to sustain large tensile deformation, even though only a low-volume fraction of crystalline inclusions is present.

Investigation of the Structural Heterogeneity and Corrosion Performance of the Annealed Fe-Based Metallic Glasses

“…Recently, understanding the structural heterogeneity of MGs and its relation to the intrinsic properties is an area of interest for researchers [ 9 ]. Intensive studies focused on the relationships between the structural heterogeneity of MGs and superplasticity [ 10 , 11 ], thermal expansion [ 12 ], magnetoelastic effect [ 13 ], catalytic performance for dye degradation [ 14 ], electrochemical supercapacitors [ 15 ], and hydrogen generation [ 16 ].…”

What renders bulk metallic glass ductile/brittle? -- new insight from the medium-range order

“…A former study reports that the ductility of BMGs intrinsically correlates with their STZs volumes 18 . This explains why an improved deformability/ductility of MGs was observed after imprinting, minor alloying, flash annealing, integrating crystalline phases to form composites or deformationcycling in the so-called elastic regime [3][4][5][6][7][8][9][10][37][38][39] since all these procedures stimulate topological changes by shuffling atoms/clusters and thus increase the STZ volume. The results obtained from Fig.…”

Molecular Dynamics Study of the Nanoindentation Behavior of Cu64Zr36/Cu Amorphous/Crystalline Nanolaminate Composites

“…Atomistic models as a useful supplement can provide some important information for the understanding complex microstructure evolution characteristics during nanoindentation; especially they have the indisputable advantage of characterizing the dislocation movement in crystalline materials [ 17 , 18 , 19 , 20 ] and shear bands (SB) in single-phase MGs [ 21 , 22 , 23 , 24 , 25 , 26 , 27 ], respectively. Incorporating crystalline phases mitigates the poor failure resistance in MGs, which accommodates plastic strain by dislocation slip, effectively preventing shear band propagation [ 4 , 5 , 6 , 27 , 28 , 29 ]. More recent simulation studies have confirmed that the crystalline phase inserted into the amorphous phase can impede the propagation of SBs, and plays a vital role in the plastic deformation mechanism of ACNLs [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ].…”