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ISSN 1005-0302
CN 21-1315/TG
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Current Issue
 01 June 2020, Volume 46 Issue 0 Previous Issue    Next Issue
Research Article
 Select Microstructure evolutions and interfacial bonding behavior of Ni-based superalloys during solid state plastic deformation bonding Jian Yang Zhang, Bin Xu, Naeemul Haq Tariq, MingYue Sun, DianZhong Li, Yi Yi Li J. Mater. Sci. Technol., 2020, 46 (0): 1-11.  DOI: 10.1016/j.jmst.2019.11.015 As an advanced solid state bonding process, plastic deformation bonding (PDB) is a highly reliable metallurgical joining method that produces significant plastic deformation at the bonding interface of welded joints through thermo-mechanical coupling. In this study, PDB behavior of IN718 superalloy was systematically investigated by performing a series of isothermal compression tests at various processing conditions. It was revealed that new grains evolved in the bonding area through discontinuous dynamic recrystallization (DDRX) at 1000-1150 °C. Electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) results revealed that the bonding of joints is related with interfacial grain boundary (IGB) bulging process, which is considered as a nucleation process of DRXed grain under different deformation environments. During recrystallization process, the bonded interface moved due to strain-induced boundary migration (SIBM) process. Stored energy difference (caused by accumulation of dislocations at the bonding interface) was the dominant factor for SIBM during DRX. The mechanical properties of the bonded joints were dependent upon the recrystallized microstructure and SIBM ensued during PDB.
 Select Microbiologically influenced corrosion of 304 stainless steel by halophilic archaea Natronorubrum tibetense Hongchang Qian, Lingwei Ma, Dawei Zhang, Ziyu Li, Luyao Huang, Yuntian Lou, Cuiwei Du J. Mater. Sci. Technol., 2020, 46 (0): 12-20.  DOI: 10.1016/j.jmst.2019.04.047 The corrosion behavior of 304 stainless steel (SS) in the presence of aerobic halophilic archaea Natronorubrum tibetense was investigated. After 14 days of immersion, no obvious pitting pit was observed on the SS surface in the sterile medium. By contrast, the SS exhibited serious pitting corrosion with the largest pit depth of 5.0 μm in the inoculated mediumthe inoculated medium. The X-ray photoelectron spectroscopy results indicated that the detrimental Fe2+ and Cr6+ increased in the passive film under the influence of archaea N. tibetense, which resulted in the accelerated deterioration of passive film and promoted the pitting corrosion. Combined with the energy starvation tests, the microbiologically influenced corrosion mechanism of 304 SS caused by halophilic archaea N. tibetense was discussed finally.
 Select A bottom-up strategy toward metal nano-particles modified graphene nanoplates for fabricating aluminum matrix composites and interface study Tielong Han, Enzuo Liu, Jiajun Li, Naiqin Zhao, Chunnian He J. Mater. Sci. Technol., 2020, 46 (0): 21-32.  DOI: 10.1016/j.jmst.2019.09.045 To synthesize graphene economically and efficiently, as well as to improve the interface bonding between graphene and metal and to recede the aggregation issue of graphene, in this work, an easy and scalable bottom-up strategy for the mass production of metal nanoparticles modified graphene nanoplates (GNPs) was proposed. Cu nanoparticles modified GNPs (Cu-GNPs) and Ni nanoparticles modified GNPs (Ni-GNPs) were fabricated through this method, and then compounded with Al via ball milling technique. The as-obtained Ni-GNPs/Al composite showed simultaneously improved strength and toughness compared with unreinforced Al, while the Cu-GNPs/Al composite presented a greater strengthening effect. The microstructure and interface of the two composites were carefully characterized and investigated to reveal the difference. First principle study was also adopted to explore the binding energy of different interface structures. This study could provide new insights into the fabrication of GNPs and the control of interface in GNPs/Al composites.
 Select Corrosion mechanisms of Zr-based bulk metallic glass in NaF and NaCl solutions Zhangweijia Qiu, Zhengkun Li, Huameng Fu, Hongwei Zhang, Zhengwang Zhu, Aimin Wang, Hong Li, Long Zhang, Haifeng Zhang J. Mater. Sci. Technol., 2020, 46 (0): 33-43.  DOI: 10.1016/j.jmst.2019.10.043 So far, some investigations related to the corrosion mechanism of Zr-based metallic glasses in solutions containing Cl- have been developed. However, few attentions have been paid to the situation in F--containing solution. This paper describes the corrosion behaviours of Zr52Al10Ni6Cu32 bulk metallic glass (BMG) in NaF and NaCl aqueous solutions. The corrosion mechanism of Zr-based BMG in F--containing solution was proposed for the first time. It was found that in NaCl solutions, Zr-based BMG samples underwent typical pitting corrosion. Selective dissolution of Zr, Al and enrichment of Cu were observed in corrosion pits. However, corrosion occurred in the form of general breakdown of passive film in NaF solutions. Such difference is interpreted in terms of the binding ability of anions to surrounding molecules, i.e., Cl- with loose surrounding water passes through the passive film to cause pitting; F- with a tight surrounding molecules layer absorbs on passive film then coordinates with cations from matrix.
 Select Interactions between cadmium and multiple precipitates in an Al-Li-Cu alloy: Improving aging kinetics and precipitation hardening Liang Wu, Yugang Li, Xianfeng Li, Naiheng Ma, Haowei Wang J. Mater. Sci. Technol., 2020, 46 (0): 44-49.  DOI: 10.1016/j.jmst.2019.11.032 This work demonstrates significant improvements in both the aging kinetics and precipitation hardening of an Al-Li-Cu alloy with the minor addition of Cd (0.06 at.%). The precipitation hardening effect of T1 precipitates in casting Al-Li-Cu alloys has long been ignored since it is difficult to achieve a high number density of fine precipitates without a large number of dislocations. A detailed transmission electron microscopy investigation shows that the Cd addition has changed the distribution of T1 precipitates from the conventional uneven distribution near dislocations or grain boundaries to a more homogeneous manner. Most of the Cd-rich nanoparticles were observed at the broad face and/or terminal of the T1 platelets. It is highly likely that these nanoparticles act as heterogeneous nucleation sites, which consequently leads to a higher number density of T1 precipitates. Moreover, Cd atoms were preferentially segregated within δ′ precipitates, which can be attributed to the strong bonding between Li and Cd. The interactions between Cd and the T1 (Al2CuLi) and δ′ (Al3Li) precipitates in Al-Li-Cu alloy are first reported. The present study may propose a new mechanism to effectively improve precipitation kinetics and therefore the age-hardening effect of Al-Li-Cu alloys.
 Select Heat transfer and fluid flow and their effects on the solidification microstructure in full-penetration laser welding of aluminum sheet Shaoning Geng, Ping Jiang, Xinyu Shao, Lingyu Guo, Xuesong Gao J. Mater. Sci. Technol., 2020, 46 (0): 50-63.  DOI: 10.1016/j.jmst.2019.10.027 Understanding the behaviors of heat transfer and fluid flow in weld pool and their effects on the solidification microstructure are significant for performance improvement of laser welds. This paper develops a three-dimensional numerical model to understand the multi-physical processes such as heat transfer, melt convection and solidification behavior in full-penetration laser welding of thin 5083 aluminum sheet. Solidification parameters including temperature gradient G and solidification rate R, and their combined forms are evaluated to interpret solidification microstructure. The predicted weld dimensions and the microstructure morphology and scale agree well with experiments. Results indicate that heat conduction is the dominant mechanism of heat transfer in weld pool, and melt convection plays a critical role in microstructure scale. The mushy zone shape/size and solidification parameters can be modulated by changing process parameters. Dendritic structures form because of the low G/R value. The scale of dendritic structures can be reduced by increasing GR via decreasing heat input. The columnar to equiaxed transition is predicted quantitatively via the process related G3/R. These findings illustrate how heat transfer and fluid flow affect the solidification parameters and hence the microstructure, and show how to improve microstructure by optimizing the process.
 Select Effect of molybdenum content on the microstructure and corrosion behavior of FeCoCrNiMox high-entropy alloys Chunduo Dai, Tianliang Zhao, Cuiwei Du, Zhiyong Liu, Dawei Zhang J. Mater. Sci. Technol., 2020, 46 (0): 64-73.  DOI: 10.1016/j.jmst.2019.10.020 The effect of Mo content on the microstructure revolution and corrosion behavior of cast FeCoCrNiMoxhigh-entropy alloys in chloride environments were investigated. Results indicate that FeCoCrNi and FeCoCrNiMo0.1alloys are in single FCC solid solution. The precipitates form in FeCoCrNiMo0.3 and increase in FeCoCrNiMo0.6 alloys. Pitting occurs on FeCoCrNi and FeCoCrNiMo0.1alloys while FeCoCrNiMo0.3 and FeCoCrNiMo0.6alloys suffer from preferential localized corrosion at the regions depleted in Cr and Mo. The higher Cr2O3/Cr(OH)3 ratio and the incorporation of Mo oxides make the passive film more protective and the corrosion resistance of the FeCoCrNiMo0.1alloy is thus enhanced. The correlation between microstructure and corrosion behavior and the corresponding corrosion mechanism were clarified.
Invited Review
 Select Design, preparation and measurement of protein/CNTs hybrids: A concise review Xing Zhou, Jian Su, Chenxi Wang, Changqing Fang, Xinyu He, Wanqing Lei, Chaoqun Zhang, Zhigang Huang J. Mater. Sci. Technol., 2020, 46 (0): 74-87.  DOI: 10.1016/j.jmst.2020.01.008 With the development of nanobiotechnology, the carbon nanotubes (CNTs) and protein hybrids system has attracted an increasing attention for great potential application in nanotechnology, medicine, smart materials, light industry, and biology. In this review, the main preparation processes, impact factors, measurement of interactions and potential applications of CNTs/protein are presented from the aspect of experiments. Meanwhile, the proper forces detection methods are illustrated comprehensively to complete the quantitative measurement. Atomic force microscope (AFM) and surface force apparatus (SFA) experiments are described in detail to confirm the powerful function in measuring the interaction forces. In addition, the impact of different protein structures (amino acid residues, α Helix, polypeptide chain, and assembled subunits) on interactions between CNTs and protein is presented and different amino acid residues may intervene largely on interactions. Owing to the relatively little knowledge about the structure, function, and spatial orientation of proteins interaction with CNTs surface, we assume that the key problem is how to prepare CNTs and protein specimen with unique structure (such as the variation of secondary and tridimensional structure of protein or the single CNTs) to investigate the interaction forces instead of the designed, preparation, and detection methods.
Research Article
 Select Highly efficient and stable CuZr-based metallic glassy catalysts for azo dye degradation Bowen Zhao, Zhengwang Zhu, Xin Dong Qin, Zhengkun Li, Haifeng Zhang J. Mater. Sci. Technol., 2020, 46 (0): 88-97.  DOI: 10.1016/j.jmst.2019.12.012 Metallic glasses with the unique disordered atomic structure and metastable nature have been recently applied to degrade the azo dyes and other organic pollutants based on their superior catalytic performance. In this work, the functional properties of six CuZr-based metallic glassy ribbons with the different nominal components in degrading Acid Orange Ⅱ (AO Ⅱ) azo dyes were investigated. The Cu47.5Zr46Al6.5 metallic glassy ribbons could exhibit the more advanced catalytic performance for degradation process, which could completely degrade azo dye aqueous solution within 30 min. Additionally, the Cu47.5Zr46Al6.5 metallic glassy ribbons also showed the excellent cyclic stability along with approximately 97.68 % degradation efficiency after 10 cycles. These excellent catalytic performance and stability are closely related to the synergistic effect of exposed copper nanoparticles and produced copper oxides in the reaction, which contributes to accelerate the generation of more hydroxyl radicals (·OH) to react with dye molecules. Our findings can be able to develop a novel potential metallic glassy material for the functional application of wastewater treatment.
 Select Lifecycle of cobalt-based alloy for artificial joints: From bulk material to nanoparticles and ions due to bio-tribocorrosion Zhongwei Wang, Yu Yan, Yang Wang, Yanjing Su, Lijie Qiao J. Mater. Sci. Technol., 2020, 46 (0): 98-106.  DOI: 10.1016/j.jmst.2019.12.010 The release of debris and ions from metallic artificial joints during bio-tribocorrosion posed a severe threat to patient health. In this work, the lifecycle of a CoCrMo alloy was presented by investigating the subsurface microstructure transformation in-vitro. The results showed that the originally coarse grains changed to nano-grains (NGs) on the top region of the alloy, and nanoparticles (NPs) were torn off the surface, which were then blocked by the tribo-film. The agglomerated alloy NPs contained in the tribo-film transformed into debris after being removed from the alloy surface. The majority of the torn-off NPs were corroded and released ions into solution due to their high chemical activities.
 Select Natural-ageing-enhanced precipitation near grain boundaries in high-strength aluminum alloy Peipei Ma, Chunhui Liu, Qiuyu Chen, Qing Wang, Lihua Zhan, Jianjun Li J. Mater. Sci. Technol., 2020, 46 (0): 107-113.  DOI: 10.1016/j.jmst.2019.11.035 Artificial ageing above 165 °C directly after quenching induces the formation of ~50 nm wide precipitate-free zone (PFZ) and ~100 nm wide precipitate-sparse zone (PSZ) consisting of coarse precipitates with a gradient in size and density toward the grain center in a commercial Al-Zn-Mg-Cu alloy. With the grain size decreasing, the fraction of PFZ and PSZ in a grain becomes larger and could even occupy the entire volume of the grain. This undesirable microstructure near the grain boundary is mitigated substantially by natural pre-ageing, leading to an exceptional enhancement of the age hardening potential at elevated temperatures. Natural ageing could fundamentally alter the precipitation near grain boundary, and is a promising method to optimize the precipitation hardening in high strength aluminum alloys with unconventionally small grains.
 Select Biodegradation, hemocompatibility and covalent bonding mechanism of electrografting polyethylacrylate coating on Mg alloy for cardiovascular stent Yong-Xin Yang, Zhe Fang, Yi-Hao Liu, Ya-Chen Hou, Li-Guo Wang, Yi-Fan Zhou, Shi-Jie Zhu, Rong-Chang Zeng, Yu-Feng Zheng, Shao-Kang Guan J. Mater. Sci. Technol., 2020, 46 (0): 114-126.  DOI: 10.1016/j.jmst.2019.12.011 Organic coatings are the most widely employed approach for the promotion of corrosion resistance of magnesium (Mg) alloys. Unfortunately, traditional organic coatings are weakly bonded to Mg substrates due to physical adsorption. Herein, a polyethylacrylate (PEA) coating was fabricated on Mg-Zn-Y-Nd alloy via electro-grafting. The surface structure and chemical composition were characterized by means of scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscope (AFM) and Fourier transform infrared (FTIR) as well as time of flight-secondary ion mass spectrometer (ToF-SIMS). The results showed that the surface roughness of PEA coating was dominated by scan rate; while the coverage and integrity of PEA coating were mainly affected by the monomer concentration and sweep circles. ToF-SIMS results indicated that PEA coating was wholly covered on Mg alloy, and the presence of C2H3Mg- fragment confirmed the covalent bond between PEA coating and Mg alloy. In addition, DFT calculation results of the adsorption of EA molecules with Mg substrate agree well with the experimental phenomena and observation, suggesting that the electrons in 3 s orbit of Mg atoms and 2pz orbit of C1 atom participated in the formation of covalent bond between PEA coating and Mg substrate. Potentiodynamic polarization curves and immersion test demonstrated that the PEA coatings could effectively enhance the corrosion resistance of Mg alloy. The platelet adhesion results designated that platelets were barely visible on PEA coating, which implied that PEA coating could effectively prevent the thrombosis and coagulation of platelets. PEA coating might be a promising candidate coating of Mg alloy for cardiovascular stent.
 Select The accelerating nanoscale Kirkendall effect in Co films-native oxide Si (100) system induced by high magnetic fields Yue Zhao, Kai Wang, Shuang Yuan, Yonghui Ma, Guojian Li, Qiang Wang J. Mater. Sci. Technol., 2020, 46 (0): 127-135.  DOI: 10.1016/j.jmst.2019.11.038 The morphology evolution and magnetic properties of Co films-native oxide Si (100) were investigated at 873, 973, and 1073 K in a high magnetic field of 11.5 T. Formation of Kirkendall voids in the Co films was found to cause morphology evolution due to the difference in diffusion flux of Co and Si atoms through the native oxide layer. The high magnetic fields had considerable effect on the morphology evolution by accelerating nanoscale Kirkendall effect. The diffusion mechanism in the presence of high magnetic fields was given to explain the increase of diffusion coefficient. The morphology evolution of Co films on native oxide Si (100) under high magnetic fields during annealing resulted in the magnetic properties variation.
Prospective
 Select Opportunities and challenges of biodegradable Zn-based alloys H.F. Li, Z.Z. Shi, L.N. Wang J. Mater. Sci. Technol., 2020, 46 (0): 136-138.  DOI: 10.1016/j.jmst.2019.12.014 Following the footsteps of biodegradable Mg-based and Fe-based alloys, biodegradable Zn-based alloy is a newcomer and rising star in the family of biodegradable metals and alloys. The combined superior mechanical properties, appropriate degradation rates, excellent biocompatibility of biodegradable Zn-based alloys have brought worldwide research interest on the design, development and clinical translation of Zn-based alloys. The present perspective has summarized opportunities and challenges in the development of biodegradable Zn-based alloys.
Research Article
 Select Surface energy-driven solution epitaxial growth of anatase TiO2 homostructures for overall water splitting Shi Li, Luoyuan Ruan, Shanpeng Wang, Zhiyu Wang, Zhaohui Ren, Gaorong Han J. Mater. Sci. Technol., 2020, 46 (0): 139-144.  DOI: 10.1016/j.jmst.2020.01.038 Titanium dioxide (TiO2) has been extensively investigated as a photocatalyst for water splitting to produce H2. However, an overall water splitting by using anatase TiO2 is extremely difficult due to the short lifetime of holes. In this work, we propose that a surface energy decrease from {001} to {101} of anatase TiO2 is able to drive an epitaxial growth. A novel anatase TiO2 homostructure has been successfully synthesized via a facile hydrothermal route, where {101} semi-pyramid nanoparticles epitaxially grew on the both sides of the {001} nanosheets. The epitaxial relationship between the nanoparticles and the nanosheets has been characterized to be {001}//{001} of anatase TiO2. For the first time, it is interesting to find that the homostructure with 12 wt% of {101} semi-pyramid can significantly improve the H2 evolution rate by nearly 5 times compared to the pure nanosheets under the ultraviolet irradiation. More importantly, such homostructure enables 10.78 μmol g-1 h-1 of O2 production whereas the pure nanosheets cannot evolve detectable O2 gas. Meanwhile, the time-resolved photoluminescence analysis indicates that the mean lifetime of the holes is increased from 2.20 ns of the nanosheets to 3.59 ns of the homostructure, accounting for the observed overall water splitting. The findings suggest that constructing a homostructure by a surface energy strategy could be promising towards overall water splitting, which may be applicable to other photocatalytic materials.
 Select Design materials based on simulation results of silicon induced segregation at AlSi10Mg interface fabricated by selective laser melting Yucheng Ji, Chaofang Dong, Decheng Kong, Xiaogang Li J. Mater. Sci. Technol., 2020, 46 (0): 145-155.  DOI: 10.1016/j.jmst.2020.01.037 AlSi10Mg fabricated by selective laser melting (SLM) had a unique network-like silicon-rich structure, and the mechanism for its formation was explained by molecular dynamics (MD) simulations. The effects of the silicon-rich phase and Mg-containing structure on corrosion were studied by first-principles methods. According to the simulations, corrosion resistant materials were designed, samples with laser powers of 150 W, 200 W and 250 W were fabricated. The results indicated that a local thermal gradient during laser printing caused Si segregation, and the rapid cooling rate lead to a large number of subgrains, which assisted precipitation. The difference in potential caused galvanic corrosion, and a structure with low work function in the molten pool caused pitting. The corrosion resistance of materials processed with a high laser power increased.
 Select Recycled low-temperature direct bonding of Si/glass and glass/glass chips for detachable micro/nanofluidic devices Chenxi Wang, Hui Fang, Shicheng Zhou, Xiaoyun Qi, Fanfan Niu, Wei Zhang, Yanhong Tian, Tadatomo Suga J. Mater. Sci. Technol., 2020, 46 (0): 156-167.  DOI: 10.1016/j.jmst.2019.11.034 Silicon and glass are two of the most ideal materials for micro/nanofluidic devices, which have been widely used for research in multidisciplinary fields. However, many micro/nanofluidic devices enable only single use due to the irreversible bonding between Si/glass or glass/glass chips. If the silicon- and glass-based devices are fabricated to be detachable, the substrates can be reused and bonded again without repeating expensive micro/nanofabrication processes. Herein, we present a recycled direct bonding method for Si/glass and glass/glass chips based on oxygen plasma activation and low-temperature annealing processes. Strong bonding strength and void-free bonding interface are obtained after annealing at 150 °C. The surfaces and the bonding interfaces are characterized to elucidate the bonding mechanisms. Moreover, immersion tests are carried out to investigate the interfacial corrosion resistance in various chemical and biological solutions as well as explore a detachable method. The bonding strengths are controlled to meet the demand for micro/nanofluidic devices and the bonding interfaces can be separated in ethanol. As a result, we succeed in the experiment of bonding and detaching of glass substrates without fracturing, which is repeated for three times.
 Select Influence of texture distribution in magnesium welds on their non-uniform mechanical behavior: A CPFEM study Weijie Ren, Dejia Liu, Qing Liu, Renlong Xin J. Mater. Sci. Technol., 2020, 46 (0): 168-176.  DOI: 10.1016/j.jmst.2020.01.035 Recent studies indicate that the texture distribution in friction stir welded (FSW) Mg alloys can be tailored and hence improve the joint performance. In this work, a crystal plasticity finite element modeling (CPFEM) was performed to understand the effects of texture distribution in stir zone (SZ) on the non-uniform plastic deformation and fracture localization. In total, six kinds of observed or purposely tilted texture distributions were modelled. The “concave-convex” appearance, as commonly observed in the tensile sample, was successfully simulated. It reveals that the mirror-symmetrical distribution of basal planes in the region of easy to activate basal slip (EABS) determined the “concave-convex” appearance in SZ-center. The asymmetrical appearance exchanged on plane A and plane B when the directions of basal planes were switched in the two EABS regions. Furthermore, the asymmetrical feature of plastic deformation was changed with varying the texture distribution in SZ. The “embossed” feature became more obvious in SZ-center first, and then gradually weakened with the c-axis rotated away from the weld plate plane. Severe necking was successfully simulated in SZ-center of FSW-H joint and in SZ-side of FSW-L joint. That might determine the observed fracture morphology. We believe that this simulation study is helpful for further improving the performance of FSW Mg joints.
 Select Phosphide-oxide honeycomb-like heterostructure CoP@CoMoO4/CC for enhanced hydrogen evolution reaction in alkaline solution Zheng Liu, Jieqiong Wang, Changhong Zhan, Jing Yu, Yang Cao, Jinchun Tu, Changsheng Shi J. Mater. Sci. Technol., 2020, 46 (0): 177-184.  DOI: 10.1016/j.jmst.2019.12.013 The design and construction of effective and stable hydrogen evolution reaction (HER) catalysts represent the key to obtaining hydrogen energy economically. Transition metal phosphides (TMPs) have attracted considerable attention due to their unique catalytic mechanism, which is similar to hydrogenase. However, single-phase TMPs remain limited by their low activity and weak stability in alkaline solutions. In this work, CoP@CoMoO4 nanosheets with phosphide and oxide heterostructure were synthesized on carbon cloth (CC) through hydrothermal method and subsequently reacted with red phosphorus in a tube furnace. The outstanding synergy between CoP and CoMoO4 enhanced the HER activity and stability in alkaline solution. The CoP@CoMoO4/CC heterostructure exhibited excellent HER activity with a low overpotential of 89 mV at 10 mA cm-2 with Tafel slope of 69 mV dec-1, and outstanding stability when compared with single-phase phosphides. Our present research provides a new approach for the preparation of inexpensive, highly active, and highly durable phosphorus-based catalyst for HER.
 Select Environmental friendly synthesis of hierarchical mesoporous platinum nanoparticles templated by fucoidan biopolymer for enhanced hydrogen evolution reaction Seung Man Lim, Kyunglee Kang, Hongje Jang, Jung Tae Park J. Mater. Sci. Technol., 2020, 46 (0): 185-190.  DOI: 10.1016/j.jmst.2020.01.036 Researching novel hydrogen evolution reaction (HER) catalysts with enhanced electrocatalytic activity, excellent stability, and cost-efficiency is of great significance for the large-scale hydrogen production from industrial electrolysis technology. We report the preparation of hierarchical mesoporous-Pt nanoparticles (HM-PtNPs) with coral-like rough surface morphologies using environmental friendly and biocompatible fucoidan (Fu) biopolymer as a surface engineering compound and its application to electrocatalysts for water-splitting. The designed HM-PtNPs yields better mass activity of electrocatalysts compared to a commercial Pt/C. HM-PtNPs showed an overpotential of 33 mV at 10 mA cm-2 for the HER in 0.5 M H2SO4, which was highly comparable to that of the commercial Pt/C catalysts (29 mV). However, the amount of HM-PtNPs loaded in glassy carbon electrode (0.033 mg mL-1) was approximately 20 times lower than that of the commercial Pt/C (0.64 mg mL-1. The HM-PtNPs also maintained high catalytic stability with a consistent HER current density after 1000 continuous operation. The excellent HER performance is attributed to the improved electrochemical surface area, highly porous structure, and good surface wettability of the HM-PtNPs, which results in enhanced electrocatalytic activity, decreased resistance at the electrode/electrolyte interface, and facile penetration of the electrolytes inside the electrode.
 Select Microstructure and fatigue behavior of laser-powder bed fusion austenitic stainless steel Chenfan Yu, Peng Zhang, Zhefeng Zhang, Wei Liu J. Mater. Sci. Technol., 2020, 46 (0): 191-200.  DOI: 10.1016/j.jmst.2019.08.047 The microstructures and stress-controlled fatigue behavior of austenitic stainless steel (AISI 316 L stainless steel) fabricated via laser-powder bed fusion (L-PBF) technique were investigated. For L-PBF process, zigzag laser scanning strategy (scan rotation between successive layer was 0°, ZZ sample) and cross-hatching layer scanning strategy (scan rotation between successive layer was 67°, CH sample) were employed. By inducing different thermal history, it is found that the scan strategies of laser beam have a significant impact on grain size and morphology. Fatigue cracks generally initiated from persistent slip bands (PSBs) or grain boundaries (GBs). It is observed that PSBs could transfer the melt pool boundaries (MPBs) continuously. The MPBs have better strain compatibility compared with grain boundaries (GBs), thus MPBs would not be the initiation site of fatigue cracks. A higher fatigue limit strength could be achieved by employing a crosshatching scanning strategy. For the CH sample, fatigue cracks also initiated from GBs and PSBs. However, fatigue crack initiated from process-induced defects were observed in ZZ sample in high-cycle regions. Solidification microstructures and defects characteristics are important factors affecting the fatigue performance of L-PBF 316 L stainless. Process-induced defects originated from fluid instability can be effectively reduced by adjusting the laser scan strategy.
 Select A novel Cu-bearing high-entropy alloy with significant antibacterial behavior against corrosive marine biofilms Enze Zhou, Dongxu Qiao, Yi Yang, Dake Xu, Yiping Lu, Jianjun Wang, Jessica A. Smith, Huabing Li, Hongliang Zhao, Peter K. Liaw, Fuhui Wang J. Mater. Sci. Technol., 2020, 46 (0): 201-210.  DOI: 10.1016/j.jmst.2020.01.039 The design of novel high-entropy alloys (HEAs) provides a unique opportunity for the development of structure-function integrated materials with high mechanical and antimicrobial properties. In this study, by employing the antibacterial effect of copper, a novel Al0.4CoCrCuFeNi HEA with broad-spectrum antibacterial and strong mechanical properties was designed. High concentrations of copper ions released from the HEA prevented growth and biofilm formation by biocorrosive marine bacterial species. These findings serve as a proof-of-concept for further development of unique HEA materials with high antimicrobial efficiency and mechanical properties, compared to conventional antibacterial alloys.
 Select Principle for obtaining high joint quality in dissimilar friction welding of Ti-6Al-4V alloy and SUS316L stainless steel Huihong Liu, Yo Aoki, Yasuhiro Aoki, Kohsaku Ushioda, Hidetoshi Fujii J. Mater. Sci. Technol., 2020, 46 (0): 211-224.  DOI: 10.1016/j.jmst.2019.10.037 Ti-6Al-4V alloy (Ti64) and SUS316L stainless steel rods were dissimilarly friction welded. Especially focusing on the detailed observation of interface microstructural evolution during the friction welding (FW), the relationship between the processing conditions, weld interface microstructure, and mechanical properties of the obtained joints were systematically investigated to elucidate the principle for obtaining a high joint quality in the FW of Ti64 and SUS316L. A higher friction pressure produced a lower welding temperature in the FW, hence suppressing the thick intermetallic compound layer formation. However, hard and brittle Ti64/SUS316L mechanically mixed layers generally formed especially at the weld interface periphery due to the high temperature increasing rate, high rotation linear velocity and high outward flow velocity of the Ti64. These harmful layers tended to induce the cracks/voids formation at the weld interfaces hence deteriorating the joints’ mechanical properties. The rotation speed reduction and liquid CO2 cooling during the entire processing decreased the temperature increasing rate, rotation linear velocity and outward flow velocity of the Ti64 at the weld interface periphery. Therefore, they suppressed the formation of the harmful mechanically mixed layers, facilitated the homogeneous and sound interface microstructure generation, and finally produced a high-quality dissimilar joint in the FW of Ti64 and SUS316L.
 Select Variation in dynamic deformation behavior and resultant yield asymmetry of AZ80 alloy with extrusion temperature Sang-Hoon Kim, Sang Won Lee, Byoung Gi Moon, Ha Sik Kim, Sung Hyuk Park J. Mater. Sci. Technol., 2020, 46 (0): 225-236.  DOI: 10.1016/j.jmst.2019.11.033 In this work, variation in the dynamic recrystallization (DRX) and dynamic precipitation behavior of AZ80 alloy during extrusion due to changes in extrusion temperature was investigated, and the resultant microstructure and yield asymmetry were analyzed. As the extrusion temperature increases from 250 °C to 350 °C, the primary DRX mechanism changes from twin-induced DRX to discontinuous DRX, resulting in an increase in the DRX area fraction and unDRXed grain size. In addition, as the extrusion temperature rises, Mg17Al12 precipitation during extrusion decreases sharply throughout the extruded material. The reduction in the compressive yield strength (CYS) with increasing extrusion temperature is more pronounced than it is for the tensile yield strength (TYS), which ultimately increases the yield asymmetry of the extruded material. The higher extrusion temperature has less of an influence on the TYS due to the promotion of certain hardening effects. On the other hand, the greater reduction in the CYS is attributed to the increased fraction and size of regions in which {10$\bar{1}$2} twins predominantly form and the lower amount of precipitates, which effectively facilitates {10$\bar{1}$2} twinning.
 Select Halloysite nanotubes loaded with nano silver for the sustained-release of antibacterial polymer nanocomposite scaffolds Wang Guo, Wei Liu, Li Xu, Pei Feng, Yanru Zhang, Wenjing Yang, Cijun Shuai J. Mater. Sci. Technol., 2020, 46 (0): 237-247.  DOI: 10.1016/j.jmst.2019.11.019 It is challenging for antibacterial polymer scaffolds to achieve the drug sustained-release through directly coating or blending. In this work, halloysite nanotubes (HNTs), a natural aluminosilicate nanotube, were utilized as a nano container to load nano silver (Ag) into the lumen through vacuum negative-pressure suction & injection and thermal decomposition of silver acetate. Then, the nano Ag loaded HNTs (HNTs@Ag) were introduced to poly-l-lactic acidide) (PLLA) scaffolds prepared by additive manufacturing for the sustained-release of Ag+. Acting like a 'shield', the tube walls of HNTs not only retarded the erosion of external aqueous solution on internal nano Ag to generate Ag+ but also postponed the generated Ag+ to diffuse outward. The results indicated the PLLA-HNTs@Ag nanocomposite scaffolds achieved a sustained-release of Ag+ over 28 days without obvious initial burst release. Moreover, the scaffolds exhibited a long-lasting antibacterial property without compromising the cytocompatibility. Besides, the degradation properties, biomineralization ability and mechanical properties of the scaffolds were increased. This study suggests the potential application of inorganic nanotubes as drug carrier for the sustained-release of functional polymer nanocomposite scaffolds.
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