Crystal Chemistry and Physical Properties of A Quaternary Intermetallic Compound, θ-(Al0.8718Cu0.0256Si0.1026)13Fe4

Copyright © 2022 by the authors. θ-Al13Fe4 particles form as a primary Fe intermetallic compound (Fe-IMC) during the casting of commercial Al metals and alloys that inevitably contain Fe and Si as impurities. Moreover, the excellent mechanical performances of the Al-Cu alloys demand knowledge about the structural chemistry of the Fe-IMCs, including the θ-phase in the quaternary Al-Cu-Fe-Si system. Here, we investigate the stability, crystal structure, and electronic and mechanical properties of the Cu and Si co-doped θ-phase using a first-principles density-functional theory approach. The calculations reveal high stability of a quaternary θ-phase with chemical composition (Al0.8718Cu0.0256Si0.1026)13Fe4 at ambient conditions. Thermodynamics and statistical analysis show a broad range of Si content in the structure at the casting temperature. The Cu and Si (co-)doping enhances the bulk modulus of the compounds. The calculated bulk modulus of the quaternary θ-phase is 129 GPa. The findings help characterize the θ-phase in the quaternary Al-Si-Fe-Cu system and understand the formation of the θ-phase and related phase transformations in the various Al alloys during casting.This research was funded by EPSRC (UK) under grant number EP/N007638/1 and EP/S005102/1

High-performance acceleration of 2-D and 3D CNNs on FPGAs using static block floating point

Over the past few years, 2-D convolutional neural networks (CNNs) have demonstrated their great success in a wide range of 2-D computer vision applications, such as image classification and object detection. At the same time, 3-D CNNs, as a variant of 2-D CNNs, have shown their excellent ability to analyze 3-D data, such as video and geometric data. However, the heavy algorithmic complexity of 2-D and 3-D CNNs imposes a substantial overhead over the speed of these networks, which limits their deployment in real-life applications. Although various domain-specific accelerators have been proposed to address this challenge, most of them only focus on accelerating 2-D CNNs, without considering their computational efficiency on 3-D CNNs. In this article, we propose a unified hardware architecture to accelerate both 2-D and 3-D CNNs with high hardware efficiency. Our experiments demonstrate that the proposed accelerator can achieve up to 92.4% and 85.2% multiply-accumulate efficiency on 2-D and 3-D CNNs, respectively. To improve the hardware performance, we propose a hardware-friendly quantization approach called static block floating point (BFP), which eliminates the frequent representation conversions required in traditional dynamic BFP arithmetic. Comparing with the integer linear quantization using zero-point, the static BFP quantization can decrease the logic resource consumption of the convolutional kernel design by nearly 50% on a field-programmable gate array (FPGA). Without time-consuming retraining, the proposed static BFP quantization is able to quantize the precision to 8-bit mantissa with negligible accuracy loss. As different CNNs on our reconfigurable system require different hardware and software parameters to achieve optimal hardware performance and accuracy, we also propose an automatic tool for parameter optimization. Based on our hardware design and optimization, we demonstrate that the proposed accelerator can achieve 3.8-5.6 times higher energy efficiency than graphics processing unit (GPU) implementation. Comparing with the state-of-the-art FPGA-based accelerators, our design achieves higher generality and up to 1.4-2.2 times higher resource efficiency on both 2-D and 3-D CNNs

Heterogeneous Nucleation of Eutectic Structure in Al-Mg-Si Alloys

Copyright © The Author(s) 2020. The microstructure of Al-5Mg-2Si-0.4Mn-0.7Fe alloy solidified at different conditions were examined. Different kinds of eutectic structures such as (Al15(Fe,Mn)3Si2 + α-Al), (Mg2Si + α-Al) and (FIMCs + Mg2Si + α-Al) were selected due to the different primary phases formation. The phase relationships between the phases within the eutectic structures, and the phase relationships between the primary phases and the eutectic leading phases were investigated. A well-defined orientation relationship (OR) between α-Al15(FeMn)3Si2 and Mg2Si was examined

Crystal chemistry and electronic structure of the β-AlFeSi phase from first-principles

Supplementary data are available online at https://www.sciencedirect.com/science/article/pii/S0022459621002449?via%3Dihub#appsec1 .β-AlFeSi has a layered structure composed of FeAlSi blocks and exhibits a rich variety of crystal chemistry. Plate-like/rod-like β-AlFeSi particles formed in Al-based alloys have nontrivial influences on the mechanical performance of the cast parts. Here, we investigate the stability, crystal chemistry and electronic structure of the β-phase using the first-principles density-functional theory (DFT) method. We reveal that Si prefers on the Al1 or Al6 sites, forming stable β-Al4.5SiIFe or β-Al4.5SiVIFe (the Roman numerals represent the Al sites in the Rømming’s labels). This differs from the existing model with a homogeneous Si/Al distribution. Moreover, the calculations also find that stacking of the FeAlSi blocks leads to structural transformations. Electronically β-Al4.5SiFe is anisotropic with a narrow pseudo-band-gap, indicating its unusual physical properties. The obtained information here sheds some light not only on the stability and crystal chemistry of the β-phase as a member of the large family of the Fe-containing intermetallic compounds in Al-based alloys, but also on its potential applications as low-dimensional functional materials.EPSRC (UK) under grant numbers EP/N007638/1 and EP/S005102/1

Luttinger Parameter g for Metallic Carbon Nanotubes and Related Systems

The random phase approximation (RPA) theory is used to derive the Luttinger parameter g for metallic carbon nanotubes. The results are consistent with the Tomonaga-Luttinger models. All metallic carbon nanotubes, regardless if they are armchair tubes, zigzag tubes, or chiral tubes, should have the same Luttinger parameter g. However, a (10,10) carbon peapod should have a smaller g value than a (10,10) carbon nanotube. Changing the Fermi level by applying a gate voltage has only a second order effect on the g value. RPA theory is a valid approach to calculate plasmon energy in carbon nanotube systems, regardless if the ground state is a Luttinger liquid or Fermi liquid. (This paper was published in PRB 66, 193405 (2002). However, Eqs. (6), (9), and (19) were misprinted there.)Comment: 2 figure

Crystal Chemistry and Electronic Properties of the Al-Rich Compounds, Al2Cu, ω-Al7Cu2Fe and θ-Al13Fe4 with Cu Solution

Copyright: 2022 by the authors. In this work, we investigate Cu solution in θ-Al13Fe4 and related Al-rich ω-Al7Cu2Fe and Al2Cu phases in the Al-Cu-Fe system using the first-principles density functional theory (DFT) with on-site Coulomb interaction correction. The results show preference of Cu at Al7, forming a ternary θ-Al76Cu2Fe24 at ambient conditions, and both Al7 and Al9 sites (in Grin’s note), forming θ-(Al76−xCu2+x)Fe24 at a high temperature. The relative stability of the Al-rich compounds and their crystal and electronic properties are investigated. We show the importance of the Hubbard U correction to the standard DFT functionals for Cu-containing metallic materials. This study helps characterize the intermetallic compounds in Cu-containing Al alloys, and helps further control Fe-containing intermetallic compounds in the solidification of Al-based alloys.EPSRC (UK) under grant numbers EP/N007638/1 and EP/S005102/1

A New Atomistic Mechanism for Heterogeneous Nucleation in the Systems with Negative Lattice Misfit: Creating a 2D Template for Crystal Growth

© 2021 by the authors. Heterogeneous nucleation is a widespread phenomenon in both nature and technology. However, our current understanding is largely confined to the classical nucleation theory (CNT) postulated over a century ago, in which heterogeneous nucleation occurs stochastically to form a spherical cap facilitated by a substrate. In this paper, we show that heterogeneous nucleation in systems with negative lattice misfit completes deterministically within three atomic layers by structural templating to form a two-dimentional template from which the new phase can grow. Using molecular dynamics (MD) simulations of a generic system containing metallic liquid (Al) and a substrate of variable lattice misfit (fcc lattice with fixed Al atoms), we found that heterogeneous nucleation proceeds layer-by-layer: the first layer accommodates misfit through a partial edge dislocation network; the second layer twists an angle through a partial screw dislocation network to reduce lattice distortion; and the third layer creates a crystal plane of the solid (the 2D nucleus) that templates further growth. The twist angle of the solid relative to the substrate as a signature of heterogeneous nucleation in the systems with negative lattice misfit has been validated by high resolution transmission electron microscopic (HRTEM) examination of TiB2/Al and TiB2/α-Al15(Fe, Mn)3Si2 interfaces in two different Al-alloys.This work has been funded by the EPSRC of the UKRI under the grant number EP/N007638/1

Composition templating for heterogeneous nucleation of intermetailic compounds

Heterogeneous nucleation of intermetallic compounds (IMCs) is inherently more difficult than that of a pure metal or a solid solution. It requires not only the creation of a crystal structure but also the positioning of 2 or more types of elements in the lattice with specified compositions. This makes composition templating a very important approach to nucleation control in addition to structural templating. In this paper we demonstrate composition templating as an approach to enhancing heterogeneous nucleation of IMCs. We found that heterogeneous nucleation of Fe-bearing IMCs in Al-alloys requires a undercooling few tens of K, which is more than an order of magnitude higher than that for solid solutions. Segregation of Fe to the TiB2 surface (the Fe modified TiB2) can provide composition templating and hence enhance heterogeneous nucleation of -Al15(Fe, Mn)3Si2 resulting in a significant grain refinement.EPSRC Grant EP/H026177/1

Impeding Nucleation for More Significant Grain Refinement

© 2020, The Author(s). Grain refinement has been a topic of extensive research due to its scientific and technological importance as a common industrial practice for over seven decades. The traditional approach to grain refinement has been to reduce nucleation undercooling by the addition of potent nucleant particles. Here we show both theoretically and experimentally that more significant grain refinement can be achieved through increasing nucleation undercooling by using impotent nucleant particles. Based on the concept of explosive grain initiation, this new approach is illustrated by grain initiation maps and grain refinement maps and validated by experiments. It is anticipated that this new approach may lead to a profound change in both nucleation research and industrial practice well beyond metal casting.EPSRC (grant number EP/N007638/1)

Two novel transcriptional regulators are essential for infection-related morphogenesis and pathogenicity of the rice blast fungus Magnaporthe oryzae.

This is the final version of the article. Available from the publisher via the DOI in this record.The cyclic AMP-dependent protein kinase A signaling pathway plays a major role in regulating plant infection by the rice blast fungus Magnaporthe oryzae. Here, we report the identification of two novel genes, MoSOM1 and MoCDTF1, which were discovered in an insertional mutagenesis screen for non-pathogenic mutants of M. oryzae. MoSOM1 or MoCDTF1 are both necessary for development of spores and appressoria by M. oryzae and play roles in cell wall differentiation, regulating melanin pigmentation and cell surface hydrophobicity during spore formation. MoSom1 strongly interacts with MoStu1 (Mstu1), an APSES transcription factor protein, and with MoCdtf1, while also interacting more weakly with the catalytic subunit of protein kinase A (CpkA) in yeast two hybrid assays. Furthermore, the expression levels of MoSOM1 and MoCDTF1 were significantly reduced in both Δmac1 and ΔcpkA mutants, consistent with regulation by the cAMP/PKA signaling pathway. MoSom1-GFP and MoCdtf1-GFP fusion proteins localized to the nucleus of fungal cells. Site-directed mutagenesis confirmed that nuclear localization signal sequences in MoSom1 and MoCdtf1 are essential for their sub-cellular localization and biological functions. Transcriptional profiling revealed major changes in gene expression associated with loss of MoSOM1 during infection-related development. We conclude that MoSom1 and MoCdtf1 functions downstream of the cAMP/PKA signaling pathway and are novel transcriptional regulators associated with cellular differentiation during plant infection by the rice blast fungus.Funding: This work was supported by National Key Basic Research and Development Program of China (2012CB114002), by Program for Changjiang Scholars and Innovative Research Team in University (IRT0943), by the Natural Science Foundation of China (Grant Nos. 30970129 and 31071648) and the Doctoral Fund of Ministry of Education of China (20100101110097) to ZW