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The gradient Al2O3 layer coated bimodal structured composite substrate was fabricated using combined chemical and hydrothermal processes. Selective etching was performed to remove micrometer-sized α-Al dendrites from the ultrafine structured matrix. Simultaneously, a hydrothermal oxidation process was used to grow Al2O3 on the surface of the porous structured substrate. In particular, the architecture of coated metal oxide (Al2O3) can be altered from a rectangular to a pyramidal shape depending on the hydrothermal process time. Keywords: Ultrafine eutectic composite, Porous materials, Dealloying, Hydrothermal process

In the field of surface mount technology (SMT), early detection of defects in production machines is crucial to prevent yield reduction. In order to detect defects in the production machine without attaching additional costly sensors, attempts have been made to classify defects in solder paste printers using defective solder paste pattern (DSPP) images automatically obtained through solder paste inspection (SPI). However, since the DSPP images are sparse, have various sizes, and are hardly collected, existing CNN-based classifiers tend to fail to generalize and over-fitted to the train set. Besides, existing studies employing only multi-label classifiers are less helpful since when two or more defects are observed in the DSPP image, the location of each defect can not be specified. To solve these problems, we propose a dual-level defect detection PointNet (D3PointNet), which extracts point cloud features from DSPP images and then performs the defect detection in two semantic levels: a micro-level and a macro-level. In the micro-level, a type of printer defect per point is identified through segmentation. In the macro-level, all types of printer defects appearing in a DSPP image are identified by multi-label classification. Experimental results show that the proposed D3PointNet is robust to the sparsity and size changes of the DSPP image, and its exact match score was 10.2% higher than that of the existing CNN-based state-of-the-art multi-label classification model in the DSPP image dataset.

The outstading mechanical properties of bimodal ultrafine eutectic composites (BUECs) containing length scale hierarchy in eutectic structure were demonstrated by using AFM observation of surface topography with quantitative height measurements and were interpreted in light of the details of the deformation mechanisms by three different interface modes. It is possible to develop a novel strain accommodated eutectic structure for triggering three different interface-controlled deformation modes; (I) rotational boundary mode, (II) accumulated interface mode and (III) individual interface mode. A strain accommodated microstructure characterized by the surface topology gives a hint to design a novel ultrafine eutectic alloys with excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Metallic glass (MG) assists electrical contact of screen-printed silver electrodes and leads to comparable electrode performance to that of electroplated electrodes. For high electrode performance, MG needs to be infiltrated into nanometer-scale cavities between Ag particles and reacts with them. Here, we show that the MG in the supercooled state can fill the gap between Ag particles within a remarkably short time due to capillary effect. The flow behavior of the MG is revealed by computational fluid dynamics and density funtional theory simulation. Also, we suggest the formation mechanism of the Ag electrodes, and demonstrate the criteria ofMGfor higher electrode performance. Consequently, when Al85Ni5Y8Co2MGis added in the Ag electrodes, cell efficiency is enhanced up to 20.30% which is the highest efficiency reported so far for screen-printed interdigitated back contact solar cells. These results show the possibility for the replacement of electroplating process to screen-printing process. [ABSTRACT FROM AUTHOR]

Improved room temperature plasticity was achieved by microalloying Cu in a series of (Fe71Nb6B23)100-xCux (x = 0, 0.25, 0.5, 0.75, and 1) glassmatrix alloys with tunable size and volume fraction of precipitates composed of α-Fe and Fe23B6 phases. When ~10-nm-sized nano-scale precipitates are formed with a size comparable to the shear bandwidth by controlling the added content of Cu, the (Fe71Nb6B23)99.5Cu0.5 alloy exhibits a maximum plastic strain of 4.3 ± 0.8% with pronounced multiple shear banding. A further increase in the size of the precipitates up to micrometer scale results in catastrophic fracture accompanied with irregular cracks, revealing that the fracture mechanism of the different alloys is controlled by the precipitate size. [ABSTRACT FROM AUTHOR]

The constituent phases, the microstructure, and the mechanical properties of a series of Fe87-xTi7Zr6Bx (x 5 0, 2, 4, 6, 8, 10, and 12) alloys produced by copper mold casting were investigated. Partial substitution of iron by boron in the Fe87Ti7Zr6 ultrafine eutectic alloy induces phase/microstructural evolution and simultaneously changes the mechanical properties. In the composition range of 2 ≤ x ≤ 6, the typical lamellar structure slightly changes into a spherical cellular-type eutectic. For 8 ≤ x ≤ 12, multiphase composites containing a glassy phase form. The ultrafine eutectic composites exhibit a high compressive strength of ~2.9-3.1 GPa and a distinct plasticity of ~2-8%, whereas the glassy matrix composites show a high strength of ~3.1-3.3 GPa but no observable macroscopic plasticity before failure. These findings reveal that the plasticity of heterogeneous multiphase composites is strongly related to the length scale variables and the crystallinity of the constituent phases. [ABSTRACT FROM AUTHOR]

Mg-Cu-Zn ultrafine eutectic composites with different length scale heterogeneity, consisting of micrometer size dendrites and/or ultrafine scale bimodal eutectics, exhibit high yield strength as well as good plasticity at room temperature compression. Among these alloys, micron-scale α-Mg dendrites reinforced ultrafine eutectic composites exhibit high yield strength of 310 ~ 420 MPa and large plasticity of 7 ~ 12%. Meanwhile, a Mg72Cu5Zn23 alloy comprising a bimodal eutectic structure without the micron-scale α-Mg dendrites shows the optimized mechanical properties the highest yield strength of 455 MPa combined with a considerable plastic strain of ~5%. [ABSTRACT FROM AUTHOR]

Ultrafine eutectic alloys have been developed in Ti-Ni, Ti-Fe and Ti-(Ni, Fe)-Sn alloys. The Ti76Ni24 and (Ti74Ni26)97Sn3 ultrafine eutectic alloys consist of a mixture of α-Ti and Ti2Ni phases, and β-Ti(Sn) and Ti2Ni phases, respectively, whereas the Ti70.5Fe29.5 and (Ti70.5Fe29.5)97Sn3 alloys are composed by a mixture of β-Ti(Sn) and FeTi phases with relatively spherical colony. The compression tests of Ti76Ni24, (Ti74Ni26)97Sn3 and Ti70.5Fe29.5 ultrafine eutectic alloys reveal a strength of 1400 ~ 1800 MPa with very limited plastic strain of 0.1 ~ 1%. On the contrary, a (Ti70.5Fe29.5)97Sn3 alloy exhibits high strength of 2270 MPa with enhanced plastic strain of 3.1%. Based on these results, it is feasible to suggest that the eutectic morphology and interfacial coherency between the Ti solid solution and intermetallic phases influence to control the macroscopic plasticity of the Ti-Ni and Ti-Fe ultrafine eutectic alloys. [ABSTRACT FROM AUTHOR]

A Ni–8Zr high strength ultrafine eutectic-dendrite composite with large plasticity has been developed in the Ni–Zr binary eutectic system. The excellent mechanical properties are attributed to the specific heterogeneous microstructure with distinctly different length scales, i.e., micrometer-size ductile dendrites combined with an ultrafine eutectic matrix. The plastic deformation mainly proceeds through a shear banding mechanism. However, there is no significant shear localization due to the constraint effect of ductile solid solution Ni phases including dendrites and/or alternating lamellar layers. Furthermore, excessive shear stress and accumulated shear strain can be effectively released and accommodated by delocalization and multiplication of shear bands. [ABSTRACT FROM AUTHOR]

Microstructural investigations of Fe56Nb4Al40 ultrafine eutectic-dendrite composite reveal that its high room temperature plasticity mainly originates from the evolution of slip in the dendrites and multiple shear banding in the ultrafine eutectic matrix, respectively. Here, we sequentially describe that the shear bands in the ultrafine eutectic matrix are propagated with generation of strain field in the soft alpha-Fe(Al) layers rather than passing through by sharp shear banding in the hard (Fe,Al)2Nb intermetallic layers. Consequently, step morphologies at the interfaces of the alternating lamellae and the dendrite/eutectic matrix strongly support the effective accommodation of shear strain during shear band propagation. [ABSTRACT FROM AUTHOR]

The compositional dependence of glass formation and thermal and elastic properties was clarified for the ternary La-Al-Co bulk glass-forming system. The existing linear correlation between La concentration and characteristic temperatures, i.e., the glass transition temperature Tg and the onset temperature of crystallization Tx, as well as the elastic moduli in this system can give a useful guideline for the chemical design of desirable bulk metallic glasses (BMGs) with tunable physical properties in advance. The relationship between Tg and elastic constants for the La-Al-Co BMGs can be quantitatively described using a microscopic model proposed by T. Egami. [ABSTRACT FROM AUTHOR]

An in situ bulk ultrafine bimodal eutectic Al-Cu-Si composite was synthesized by solidification. This heterostructured composite with microstructural length scale hierarchy in the eutectic microstructure, which combines an ultrafine-scale binary cellular eutectic (a-Al + Al2Cu) and a nanometer-sized anomalous ternary eutectic (a-Al + Al2Cu + Si), exhibits high fracture strength (1.1 ± 0.1 GPa) and large compressive plastic strain (11 ± 2%) at room temperature. The improved compressive plasticity of the bimodal-nanoeutectic composite originates from homogeneous and uniform distribution of inhomogeneous plastic deformation (localized shear bands), together with strong interaction between shear bands in the spatially heterogeneous structure. [ABSTRACT FROM AUTHOR]

The effect of microstructural inhomogeneities with different length scale on the plasticity of (Ti45Zr16Be20Cu10Ni9)100-xTax (x = 0, 5, and 10) bulk glassy alloys has been studied. The formation of specific heterogeneous microstructures with a different type of structural inhomogeneity, i.e., short-/medium-range ordered clusters or micrometer-scale ductile dendrites combined with a glassy matrix, evolved by appropriately tuning the alloy chemistry, improves the room temperature plasticity up to ~12.5% and ~15%, respectively. The pronouncedly enhanced plasticity is mainly attributed to the retardation of shear localization and multiplication of shear bands by controlling the plastic and failure instabilities otherwise responsible for premature failure. [ABSTRACT FROM AUTHOR]

The evolution of microstructure and its influence on the mechanical properties of high-strength ultrafine eutectic Fe-(Ti, Zr)-(B, Co) alloys has been studied. The addition of B or Co improves the room temperature compressive plasticity from 1% to ~8.5% or ~14%, respectively, due to the formation of a heterogeneous microstructure with distinctly different length scales, which can delay the propagation of shear bands and promotes the activation of multiple shear bands. [ABSTRACT FROM AUTHOR]

The effects of niobium (Nb) addition on the glass-forming ability (GFA), crystallization behavior, and compressive mechanical property of iron (Fe)-boron (B)-yttrium (Y) alloys have been investigated. Among the (Fe71.2B24Y4.8)100-xNbx (x = 0, 2, 4, 6, 8) alloys investigated, (Fe71.2B24Y4.8)96Nb4 exhibits the highest GFA, enabling the formation of glassy rods with a maximum diameter of 7 mm, which is the largest among quaternary Fe-based alloys. The comparison of the crystallization behavior of the alloys shows that the formation of metastable Fe23B6 phase during crystallization in the (Fe71.2B24Y4.8)96Nb4 alloy can suppress the formation of other stable crystalline phases such as a-Fe, enhancing the stability of the glass phase. The present results show that the attainment of a significantly high GFA is possible even in a quaternary Fe-based alloy system by properly tailoring the competing crystalline phase by the modification of liquid chemistry. [ABSTRACT FROM AUTHOR]