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

Abstract

ZrCu-based bulk metallic glass composites (BMGCs) are well known for their plastic deformability, superior to traditional metallic glasses (MGs), which is attributed to a unique dual-phases structure, namely, the glassy matrix and unstable B2 phase. In the present study, in-situ tensile testing is used to trace the deformation process of a ZrCu-based BMGC. Three deformation stages of the BMGC, i.e., the elastic-elastic stage, the elastic-plastic stage, and the plastic-plastic stage are identified. In the elastic-elastic and elastic-plastic stages, the yield strength and elastic limit are major influenced by the volume fraction of the B2 crystals. In the plastic-plastic stage, the B2 phase stimulates the formation of multiple shear bands and deflects the direction of shear bands by disturbing the stress field in front of the crack tip. The deformation-induced martensitic transformation of the metastable B2 phase contributes to the plasticity and work hardening of the composite. This study highlights the formation and propagation of multiple shear bands and reveals the interactions of shear bands with structural heterogeneities in situ. Especially, the blocking of shear bands by crystals and the martensitic transformation of the B2 phase are critical for the mechanistic deformation process and illustrate the function of the B2 phase in the present BMGCs.

In situ TEM observation of phase transformation in bulk metallic glass composites

“…In summary, quantitative in situ tensile testing in the TEM has revealed the effects of phase transformation on the deformation of a BMGC. Differently from previous reports that shear banding happens in the glassy matrix first and get blocked by or trigger phase transformation in the crystalline precipitates [16,17], it is directly visualized that in a BMGC with metastable crystalline β phase, phase transformation occurs in the crystals first and likely produces preferential sites for shear banding during deformation. The current work sheds light on the complex deformation process in a BMGC exhibiting a TRIP effect and therefore serves as viable input for simulation and helps to formulate design criteria for better BMGCs.…”

“…Efforts have also been made to investigate the phase transformation using diffraction techniques [13,14]. However, due to the lack of direct nanoscale imaging of the transformation dynamics and their effects on the glassy matrix, the underlying reinforcing mechanism remains under debate, specifically whether phase transformation or shear banding occurs first [13][14][15][16][17]. In this work, we report direct observation of the phase transformation dynamics in a TiZrCuBe BMGC under tensile deformation inside a transmission electron microscope (TEM).…”

Role of Glass Composition on Mechanical Properties of Shape Memory Alloy‐Metallic Glass Composites

“…e design and fabrication of modern engineering materials are resulted from the optimization of various mechanical features such as elasticity, ductility, and strength [1][2][3]. In the case of metallic glasses (MGs), the superior strength comes at the expense of homogenous plasticity, especially at the tensile mode [4][5][6]. Hence, it is crucial to strike a balance between the strength and plasticity in the MGs.…”

Atomic arrangement in CuZr-based metallic glass composites under tensile deformation

“…[19][20][21] Up to now, the discovered parent phase with diffusionless transformation in the MG matrix is only the equiatomic CuZr intermetallic compound with a body-centered-cubic (bcc) structure (B2 phase). 22,23 This new kind of an MG composite with improvements both in tensile ductility and strength provides a novel approach for designing practical MGs with excellent performance. However, the underlying reason for the enhancements in both the tensile ductility and strength in a crystalline phase with martensitic transformation-reinforced MGs is still ambiguous.…”