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Microstructural heterogeneity and bonding strength of planar interface formed in additive manufacturing of Al–Mg–Si alloy based on friction and extrusion
Wenshen Tang, Xinqi Yang, Chaobo Tian, and  Yongsheng Xu
, https://doi.org/10.1007/s12613-022-2506-4
Abstract:
Single-pass deposits of 6061 aluminum alloy with a single-layer thickness of 4 mm were fabricated by force-controlled friction- and extrusion-based additive manufacturing. The formation characteristics of the interface, which were achieved by using a featureless shoulder, were investigated and elucidated. The microstructure and bonding strength of the final build both with and without heat treatment were explored. A pronounced microstructural heterogeneity was observed throughout the thickness of the final build. Grains at the interface with Cu, {213}<111>, and Goss orientations prevailed, which were refined to approximately 4.0 μm. Nearly all of the hardening precipitates were dissolved, resulting in the bonding interface displaying the lowest hardness. The fresh layer, subjected to thermal processes and plastic deformation only once, was dominated by a strong recrystallization texture with a Cube orientation. The previous layer, subjected twice to thermal processes and plastic deformation, was governed by P- and Goss-related components. The ultimate tensile strength along the build direction in as-deposited and heat-treated states could reach 57.0% and 82.9% of the extruded 6061-T651 aluminum alloy.
 
Enhanced copper recovery from low grade copper sulfide ores through bioleaching using residues produced by fermentation of agricultural wastes
Wei Chen, Shenghua Yin, Qing Song, Leiming Wang, and  Xun Chen
, https://doi.org/10.1007/s12613-021-2392-1
Abstract:
Effects of residues produced by agricultural wastes fermentation (AWF) on low grade copper sulfide ores bioleaching, copper recovery, and microbial community were investigated. The results indicated that adding appropriate bulk of AWF made contributions to low grade copper sulfide ores bioleaching, which may be mainly realized through reducing the passivation layer formed by Fe3+ hydrolysis. Improved copper recovery (78.35%) and bacteria concentration (9.56 × 107 cells·mL−1) were yielded in the presence of 5 g·L−1 AWF. The result of 16S rDNA analysis demonstrated that microbial community was differentiated by adding AWF. Bacteria proportion, such as Acidithiobacillus ferrooxidans, Moraxella osloensis, and Lactobacillus acetotolerans changed distinctly. Great difference between samples was showed according to beta diversity index, and the maximum value reached 0.375. Acidithiobacillus ferrooxidans accounted for the highest proportion throughout the bioleaching process, and that of sample in the presence of 5 g·L−1 AWF reached 28.63%. The results should show reference to application of agricultural wastes and low grade copper sulfide ores.
 
Evaluation and classification of rock heterogeneity based on acoustic emission detection
Tongzhao Zhang, Hongguang Ji, Xiaobo Su, Shuang You, Daolu Quan, Zhou Zhang, and  Jinzhe Li
, https://doi.org/10.1007/s12613-021-2381-4
Abstract:
For deep rock mechanics and subsurface engineering, accurately characterizing and evaluating rock heterogeneity as well as analyzing the correlation between the heterogeneity and physical and mechanical properties of rocks are critical. This study investigated the characteristics of acoustic emission signals produced in the process of strong and weak phase damage to rocks. The failure mechanisms of the strong and weak phases were analyzed by performing Brazilian splitting tests on different metagabbros and granites. The strong–weak phase ratio of the rocks and the uniformity of their spatial distribution were characterized. Test results show that as the feldspar develops, the strong-phase ratio of the metagabbro increases. However, the spatial distribution of feldspar minerals in the metagabbro becomes less uniform. The mineral spatial distribution uniformity in the altered granite is good; however, its strong-phase ratio is low. Furthermore, the strong-phase ratio of the typical granite is high; however, its mineral spatial distribution uniformity is poor. Moreover, uniaxial and triaxial test results show that the peak strength and elastic modulus of the rocks are related to the strong–weak phase ratio and mineral spatial distribution uniformity of the rocks. This study provides a new analytical method for the mechanical evaluation of deep rocks.
Research Article
Hydrogen-based direct reduction of industrial iron ore pellets: Statistically designed experiments and computational simulation
Patrícia Metolina, Tiago Ramos Ribeiro, and  Roberto Guardani
, https://doi.org/10.1007/s12613-022-2487-3
Abstract:
As part of efforts to reduce anthropogenic CO2 emissions by the steelmaking industry, this study investigated the direct reduction of industrially produced hematite pellets with H2 using the Doehlert experimental design to evaluate the effect of pellet diameter (10.5–16.5 mm), porosity (0.36–0.44), and temperature (600–1200°C). A strong interactive effect between temperature and pellet size was observed, indicating that these variables cannot be considered independently. The increase in temperature and decrease in pellet size considerably favor the reduction rate, while porosity did not show a relevant effect. The change in pellet size during the reduction was negligible, except at elevated temperatures due to crack formation. A considerable decrease in mechanical strength at high temperatures suggests a maximum process operating temperature of 900°C. Good predictive capacity was achieved using the modified grain model to simulate the three consecutive non-catalytic gas–solid reactions, considering different pellet sizes and porosities, changes during the reaction from 800 to 900°C. However, for other temperatures, different mechanisms of structural modifications must be considered in the modeling. These results represent significant contributions to the development of ore pellets for CO2-free steelmaking technology.
Research Article
Modeling of the effect of hydrogen injection on blast furnace operation and carbon dioxide emissions
Volodymyr Shatokha
, https://doi.org/10.1007/s12613-022-2474-8
Abstract:
The effect of hydrogen injection on blast furnace operation and carbon dioxide emissions was simulated using a 1D steady-state zonal model. The maximum hydrogen injection rate was evaluated on the basis of the simulation of the vertical temperature pattern in the blast furnace with a focus on the thermal reserve zone. The effects of blast temperature and oxygen enrichment were also examined to estimate coke replacement ratio, productivity, hydrogen utilization efficiency, and carbon dioxide emission reduction. For blast temperature of 1200°C, the maximum hydrogen injection rate was 19.0 and 28.3 kg of H2/t of hot metal (HM) for oxygen enrichment of 2vol% and 12vol%, respectively. Results showed a coke replacement ratio of 3–4 kg of coke/kg of H2, direct CO2 emission reduction of 10.2%–17.8%, and increased productivity by up to 13.7% depending on oxygen enrichment level. Increasing blast temperature further reduced the direct CO2 emissions. Hydrogen utilization degree reached the maximum of 0.52–0.54 H2O/(H2O + H2). The decarbonization potential of hydrogen injection was estimated in the range from 9.4 t of CO2/t of H2 to 9.7 t of CO2/t of H2. For economic feasibility, hydrogen injection requires revolutionary progress in terms of low-cost H2 generation unless the technological change is motivated by the carbon emission cost. Hydrogen injection may unfavorably affect the radial temperature pattern of the raceway, which could be addressed by adopting appropriate injection techniques.
Research Article
Review of electrodeposition methods for the preparation of high-entropy alloys
Zahra Shojaei, Gholam Reza Khayati, and  Esmaeel Darezereshki
, https://doi.org/10.1007/s12613-022-2439-y
Abstract:
High-entropy alloys (HEAs) are suitable for engineering applications requiring excellent mechanical, corrosion, thermal, and magnetic properties. In the last decade, electrodeposition has emerged as a promising synthesis technique for HEAs. Research has focused on the influence of procedure parameters on the deposition of different HEA layers and the effect of their microstructure on their corrosion and magnetic properties. This review of current literature provides comprehensive information on HEAs and the use of direct and pulse electrodeposition as a synthesis technique for these materials. This review also addresses the research gaps on HEA production via electrodeposition, such as using other ceramic particles instead of graphene oxide in composite structures based on HEAs.
Research Article
Influence of Zr and Mn additions on microstructure and properties of Mg–2.5wt%Cu–Xwt%Zn (X = 2.5, 5 and 6.5) alloys
A.V. Koltygin, V.E. Bazhenov, I.V. Plisetskaya, V.A. Bautin, A.I. Bazlov, N.Y. Tabachkova, O.O. Voropaeva, A.A. Komissarov, and  V.D. Belov
, https://doi.org/10.1007/s12613-021-2369-0
Abstract:
This work studied the effects of adding Zr and Mn in amounts less than 1wt% on the microstructure, mechanical properties, casting properties, and corrosion resistance of Mg–Zn–Cu alloys containing 2.5wt% Cu and 2.5wt%–6.5wt% Zn. The hardness and electrical conductivity measurements were used to find an optimal heat treatment schedule with the best mechanical properties. It has been established that Zr significantly increases the yield strength of the alloys due to a strong grain refinement effect. However, the presence of Mn and Zr has a detrimental effect on alloy’s elongation at fracture. It was shown that the precipitation of the Mg2Cu cathodic phase in the alloy structure negatively affects the corrosion behavior. Nevertheless, the addition of Mn decreases the corrosion rate of the investigated alloys. The best combination of the mechanical, casting, and corrosion properties were achieved in the alloys containing 2.5wt% Cu and 5wt% Zn. However, the Mn or Zr addition can improve the properties of the alloys; for example, the addition of Mn or Zr increases the fluidity of the alloys.
Research Article
Mg-intercalation engineering of MnO2 electrode for high-performance aqueous magnesium-ion batteries
Yue Zhao, Bei Wang, Minjie Shi, Shibo An, Liping Zhao, and  Chao Yan
, https://doi.org/10.1007/s12613-021-2346-7
Abstract:
Rechargeable aqueous magnesium-ion batteries (MIBs) show great promise for low-cost, high-safety, and high-performance energy storage applications. Although manganese dioxide (MnO2) is considered as a potential electrode material for aqueous MIBs, the low electrical conductivity and unsatisfactory cycling performance greatly hinder the practical application of MnO2 electrode. To overcome these problems, herein, a novel Mg-intercalation engineering approach for MnO2 electrode to be used in aqueous MIBs is presented, wherein the structural regulation and electrochemical performance of the Mg-intercalation MnO2 (denoted as MMO) electrode were thoroughly investigated by density functional theory (DFT) calculations and in-situ Raman investigation. The results demonstrate that the Mg intercalation is essential to adjusting the charge/ion state and electronic band gap of MMO electrode, as well as the highly reversible phase transition of the MMO electrode during the charging–discharging process. Because of these remarkable characteristics, the MMO electrode can be capable of delivering a significant specific capacity of ~419.8 mAh·g−1, while exhibiting a good cycling capability over 1000 cycles in 1 M aqueous MgCl2 electrolyte. On the basis of such MMO electrode, we have successfully developed a soft-packaging aqueous MIB with excellent electrochemical properties, revealing its huge application potential as the efficient energy storage devices.
Research Article
Effect of Co2+ substitution in B-sites of the perovskite system on the phase formation, microstructure, electrical and magnetic properties of Bi0.5(Na0.68K0.22Li0.10)0.5TiO3 ceramics
Pamornnarumol Bhupaijit, Chonnarong Kaewsai, Tawat Suriwong, Supree Pinitsoontorn, Surirat Yotthuan, Naratip Vittayakorn, and  Theerachai Bongkarn
, https://doi.org/10.1007/s12613-021-2345-8
Abstract:
Bi0.5(Na0.68K0.22Li0.10)0.5Ti1–xCoxO3 lead-free perovskite ceramics (BNKLT–xCo, x = 0, 0.005, 0.010, 0.015 and 0.020) were fabricated via the solid-state combustion technique. A small-amount of Co2+ ion substitution into Ti-sites led to modification of the phase formation, microstructure, electrical and magnetic properties of BNKLT ceramics. Coexisting rhombohedral and tetragonal phases were observed in all samples using the X-ray diffraction (XRD) technique. The Rietveld refinement revealed that the rhombohedral phase increased from 39% to 88% when x increased from 0 to 0.020. The average grain size increased when x increased. With increasing x, more oxygen vacancies were generated, leading to asymmetry in the bipolar strain (SE) hysteresis loops. For the composition of x = 0.010, a high dielectric constant (εm) of 5384 and a large strain (Smax) of 0.23% with the normalized strain \begin{document}$ \left({d}_{33}^{*}\right) $\end{document} of 460 pm·V–1 were achieved. The BNKLT–0Co ceramic showed diamagnetic behavior but all of the BNKLT–xCo ceramics exhibited paramagnetic behavior, measured at 50 K.
Research Article
Influence of multiple laser shock peening treatments on the microstructure and mechanical properties of Ti–6Al–4V alloy fabricated by electron beam melting
Liang Lan, Ruyi Xin, Xinyuan Jin, Shuang Gao, and  Bo He
, https://doi.org/10.1007/s12613-021-2322-2
Abstract:
Laser shock peening (LSP) is an attractive post-processing method to tailor surface microstructure and enhance mechanical performances of additive manufactured (AM) components. The effects of multiple LSP treatments on the microstructure and mechanical properties of Ti–6Al–4V part produced by electron beam melting (EBM), as a mature AM process, were studied in this work. Microstructure, surface topography, residual stress, and tensile performance of EBM-manufactured Ti–6Al–4V specimens were systematically analyzed subjected to different LSP treatments. The distribution of porosities in EBM sample was assessed via X-ray computed tomography. The results showed that EBM samples with two LSP treatments possessed a lower porosity value of 0.05% compared to the value of 0.08% for the untreated samples. The strength of EBM samples with two LSP treatments was remarkably raised by 12% as compared with the as-built samples. The grains of α phase were refined in near-surface layer, and a dramatic increase in the depth and magnitude of compressive residual stress (CRS) was achieved in EBM sample with multiple LSP treatments. The grain refinement of α phase and CRS with larger depth were responsible for the strength enhancement of EBM samples with two LSP treatments.
Research Article
Mechanism of calcium lignosulfonate in apatite and dolomite flotation system
Bo Feng, Liangzhu Zhang, Wenpu Zhang, Huihui Wang, and  Zhiyong Gao
, https://doi.org/10.1007/s12613-021-2313-3
Abstract:
Since the physical and chemical properties of apatite and dolomite can be similar, the separation of these two minerals is difficult. Therefore, when performing this separation using the flotation method, it is necessary to search for selective depressants. An experimental research was performed on the separation behavior of apatite and dolomite using calcium lignosulfonate as a depressant, and the mechanism by which this occurs was analyzed. The results show that calcium lignosulfonate has a depressant effect on both apatite and dolomite, but the depressant effect on dolomite is stronger at the same dosage. Mechanism analysis shows that the adsorptive capacity of calcium lignosulfonate on dolomite is higher than that of apatite, which is due to the strong reaction between calcium lignosulfonate and the Ca sites on dolomite. In addition, there is a hydrogen bond between calcium lignosulfonate and dolomite, which further prevents the adsorption of sodium oleate to dolomite, thus greatly inhibiting the flotation of dolomite.
Research Article
Influence of process parameters and aging treatment on the microstructure and mechanical properties of AlSi8Mg3 alloy fabricated by selective laser melting
Yaoxiang Geng, Hao Tang, Junhua Xu, Yu Hou, Yuxin Wang, Zhen He, Zhijie Zhang, Hongbo Ju, and  Lihua Yu
, https://doi.org/10.1007/s12613-021-2287-1
Abstract:
Many studies have investigated the selective laser melting (SLM) of AlSi10Mg and AlSi7Mg alloys, but there are still lack of researches focused on Al–Si–Mg alloys specifically tailored for SLM. In this work, a novel high Mg-content AlSi8Mg3 alloy was specifically designed for SLM. The results showed that this new alloy exhibited excellent SLM processability with a lowest porosity of 0.07%. Massive lattice distortion led to a high Vickers hardness in samples fabricated at a high laser power due to the precipitation of Mg2Si nanoparticles from the α-Al matrix induced by high-intensity intrinsic heat treatment during SLM. The maximum microhardness and compressive yield strength of the alloy reached HV (211 ± 4) and (526 ± 12) MPa, respectively. After aging treatment at 150°C, the maximum microhardness and compressive yield strength of the samples were further improved to HV (221 ± 4) and (577 ± 5) MPa, respectively. These values are higher than those of most known aluminum alloys fabricated by SLM. This paper provides a new idea for optimizing the mechanical properties of Al–Si–Mg alloys fabricated using SLM.