Materials by design: An experimental and computational investigation on the microanatomy arrangement of porous metallic glasses

Abstract

The correlation of a material's structure with its properties is one of the important unresolved issues in materials science research. This paper discusses a novel experimental and computational approach by which the influence of the pores on the mechanical properties of bulk metallic glasses (BMGs) can be systematically and quantitatively analyzed. The experimental stage involves the fabrication of a template whose pore configurations are pre-determined by computer-aided design tools, and replication of the designed patterns with BMGs. Quasi-static mechanical characterization of these complex microstructures is conducted under uniaxial tension and in-plane compression. For the numerical simulations, a non-local gradient-enhanced continuum mechanical model is established, using thermodynamic principles and periodic boundary conditions. The combination of the experimental and numerical results has identified the importance of the pore configuration, overall porosity and diameter to the spacing ratio of the pores to attain optimized material properties.

Mechanical and Structural Investigation of Porous Bulk Metallic Glasses

“…or lower, σflow for BMGs with high formability (e.g., Zr-and Pt-based BMGs [20]) is calculated to be 0.3 MPa, placing them in the deformation scale of the commercially available polymers [13]. The sample with embedded pores was then detached from the assembly by BMG surface polishing (the polished Si-BMG assembly is given in Figure 2b) and subsequent Si etching using a diluted KOH (35% by mass) solution (Figure 2c).…”

“…Earlier results revealed the importance of the pore design within the matrix [5,13]; the mechanical properties are optimized, as the diameter-to-spacing ratio (d/s) of the embedded pores is chosen to be between 0.5 and two. For this ideal range, the deformation is mainly controlled by the periodically-spaced pores, and thereby, the global fracture of the sample is delayed by the redirection of SBs and redistribution of the resolved shear stress around the pores.…”

“…Numerical simulations conducted by a non-local gradient-enhanced continuum mechanical model implemented by a finite element method [11,12] verify this proof of concept. The model sheds light on the scalability and versatility of this approach by using periodic boundary conditions along the external boundaries of the representative volume element [13] or by analyzing the spectrum of samples with stochastic pore designs [14]. In addition, the SB-mediated inhomogeneous plastic flow below the micron level is further regarded as the fundamental deformation mechanism for sub-micron-sized Zr-BMG pillars at no expense of yield strength [15].…”

Macroscopic tensile plasticity of Zr-based bulk metallic glass with surface screw thread shaped structure

“…For STS specimen II, the stress concentration zones have a larger size than that of STS specimen I. Thus, these larger stress concentration zones in STS specimen II usually tend to connect and form the SBs due to the geometric restrictions, which is similar to the stress distribution under the bending and compression loading [23,24] and then leads to the formation of multiple SBs as shown in Fig. 3c.…”

Fourth-order strain-gradient phase mixture model for nanocrystalline fcc materials

“…In the same line, Lapovok et al [80] proposed a physical definition of the length scale on the basis of the current dislocation cell size which is modified according to the deformation history. In the context of gradient models for metallic glasses, the length scale parameter is related to the fracture process zone size [81][82][83]. For an extensive overview of the identification and quantification of the length scale in gradient models the interested reader is referred to [84] where it is stated that a current trend is to relate the length scale parameters to the heterogeneity of the material.…”