Pulsed Laser Beam Welding of Pd\u3csub\u3e43\u3c/sub\u3eCu\u3csub\u3e27\u3c/sub\u3eNi\u3csub\u3e10\u3c/sub\u3eP\u3csub\u3e20\u3c/sub\u3e Bulk Metallic Glass

We used pulsed laser beam welding method to join Pd43Cu27Ni10P20 (at.%) bulk metallic glass and characterized the properties of the joint. Fusion zone and heat-affected zone in the weld joint can be maintained completely amorphous as confirmed by X-ray diffraction and differential scanning calorimetry. No visible defects were observed in the weld joint. Nanoindentation and bend tests were carried out to determine the mechanical properties of the weld joint. Fusion zone and heat-affected zone exhibit very similar elastic moduli and hardness when compared to the base material, and the weld joint shows high ductility in bending which is accomplished through the operation of multiple shear bands. Our results reveal that pulsed laser beam welding under appropriate processing parameters provides a practical viable method to join bulk metallic glasses

Measured optical constants of Pd_(77.5)Cu_6Si_(16.5) bulk metallic glass

Optical constants of Pd_(77.5)Cu_6Si_(16.5) alloy were determined experimentally using spectroscopic ellipsometry measurements on bulk specimens. Values of the complex refractive index of the glassy metallic alloys are compared to their crystalline counterparts and to pure crystalline Pd. The presence of Cu and Si increase the occurrence of defects in the crystal lattice resulting in reduced refractive index in the crystalline alloy when compared to pure crystalline Pd. Moreover, we show the conduction band energy of each specimen using Tauc’s plot. The obtained complex refractive index across the spectrum (250 – 1500nm) allows for accurate prediction of optical performance within the investigated spectral range providing optimal design for optical devices

3D printing metals like thermoplastics: Fused filament fabrication of metallic glasses

Whereas 3D printing of thermoplastics is highly advanced and can readily create complex geometries, 3D printing of metals is still challenging and limited. The origin of this asymmetry in technological maturity is the continuous softening of thermoplastics with temperature into a readily formable state, which is absent in conventional metals. Unlike conventional metals, bulk metallic glasses (BMGs) demonstrate a supercooled liquid region and continuous softening upon heating, analogous to thermoplastics. Here we demonstrate that, in extension of this analogy, BMGs are also amenable to extrusion-based 3D printing through fused filament fabrication (FFF). When utilizing the BMGs’ supercooled liquid behavior, 3D printing can be realized under similar conditions to those in thermoplastics. Fully dense and amorphous BMG parts are 3D printed in ambient environmental conditions resulting in high-strength metal parts. Due to the similarity between FFF of thermoplastics and BMGs, this method may leverage the technology infrastructure built by the thermoplastic FFF community to rapidly realize and proliferate accessible and practical printing of metals

Hierarchical Micro- and Nanopatterning of Metallic Glass to Engineer Cellular Responses

Nano and micropatterning of biomaterials is a rapidly evolving technology used in the engineering sciences to control cell behavior. Specifically, altering the topographies and hence surface mechanical properties has been shown to induce changes in cell morphology and function. Here, we show a method for fabricating hierarchical micro- and nanopatterns of Pt_57.5Cu_14.7Ni_5.3P_22.5 (Pt-BMG) on the relevant length scales comparable to that of proteins and cells. Leveraging the amorphous nature of Pt-BMGs, we have a versatile toolbox to manipulate patterns on the nano/micro level and combine multiple length scales to examine specific cell responses. We assay the morphology of macrophages and fibroblasts, two cell types critical to the foreign body response. Furthermore, we show that nanotopography is critical for reducing macrophage fusion and that high levels of fusion on both unpatterned and micropatterned substrates can be mitigated with the addition of nanotopographical features. Interestingly, we show that the wetting ability of the substrates does not correlate with cellular responses on these substrates. Our results suggest that the different topographical length scales can be used to systematically affect corresponding cell-type-specific responses