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The creep behavior of Fe–17Cr–1.2Cu–0.5Nb–0.01C ferritic heat-resistant stainless steel was investigated at temperatures ranging from 973 to 1123 K and stresses from 15 to 90 MPa. The evolution of precipitates after creep deformation was analyzed by scanning electron microscopy, energy dispersion spectrum, and transmission electron microscopy. The minimum creep rate decreased with the decrease in the applied load and temperature, thereby extending the rupture life. Cu-rich phase and Nb-rich Laves particles were generated in dominant quantities during the creep process, and the co-growth relationship between them could be detected. Creep rupture was featured by ductile fracture with considerable necking. As increasing the temperature and decreasing the stress, the softening of the metal matrix was accelerated, showing more obvious plastic flow. The true stress exponent and activation energy were 4.9 and 375.5 kJ/mol, respectively, indicating that the creep deformation was dominated by the diffusion-controlled dislocation creep mechanism involving precipitate-dislocation interactions. Based on the creep rupture data obtained, the Monkman–Grant relation and Larson-Miller parameter were established, which described the creep rupture life for the studied steel well.

Three powder metallurgical Ti-48Al-2Cr-2Nb compacts were prepared using spherical pre-alloyed powders, mechanically milled powders, and a mixture of the spherical pre-alloyed powders and the mechanical milled powders in a weight ratio of 1:4. Different microstructures corresponding to coarse grains, ultrafine grains, and bimodal-size grains, respectively, were obtained. The compact with a bimodal grain structure exhibits a good combination of high-yield compressive strength (~ 1393 MPa) and improved compression ratio to fracture (~ 13.9%) at room temperature due to the effects of back-stress and ductile γ-TiAl single-phase layer generated near the ultrafine/coarse grain interface. At high temperatures, the compressive properties of the compact with the bimodal grain size distribution are sensitive to the temperature. A relatively high deformation resistance is achieved at 750 °C. At this temperature, the coarse grain region of the bimodal grain-sized microstructure undergoes more strain, and the dynamic recrystallization is promoted with increasing strain, improving the ductility. By contrast, the ultrafine grains in the bimodal grain size microstructure dominate the dynamic softening when the temperature is higher than 850 °C due to their accelerated dynamic recrystallization and easy grain boundary slip that are responsible for the good formability and the sharp decrease in deformation resistance of this alloy.

It is challenging to develop Mg alloys with high strength-ductility synergy and isotropic mechanical properties. An industrial-scale ultrafine-grained (UFG) Mg-10.6Gd-2Ag wt. % alloy with excellent strength-ductility synergy and near-isotropic mechanical behavior was made by an industrial-scale rotary die equal channel angular pressing (RD-ECAP). The microstructure of the UFG alloy involves the primarily submicron α-Mg grains with an average grain size of 760.5 nm and the high-density submicron β phase (Mg5Gd) precipitates (267.8 nm). Room temperature tensile tests results reveal that the UFG alloy exhibits an over three times tensile yield strength, near two times ultimate tensile strength, and more than one and a half times elongation along three orthogonal test directions than the as-cast Mg alloy. The improvement of strength is linked to the effect of the grain boundary strengthening as well as the precipitation strengthening. The enhanced ductility is ascribed to the ultrafine grains with low dislocation density, which provide a degree of dislocation storage capacity and facilitates multiple potential deformation modes. The near-isotropic mechanical behavior stems from the weak texture and multiple deformation modes.

Silicon (Si) is commonly used in microelectronic devices and micro/nanoelectromechanical systems (MEMS/NEMS) and the mechanical behavior of nanoscale silicon is very important. However, the origin ...

In this study, the multi-pass equal channel angular pressing (ECAP) was employed on a high-calcium-content Mg-Al-Ca-Mn alloy to tailor its microstructure and mechanical properties. The obtained results showed that the network-shaped Mg2Ca and (Mg, Al)2Ca eutectic compounds in as-cast alloy were gradually crushed into ultra-fine particles after ECAP, which exhibited a bimodal particle size distribution and most aggregated at original grain boundaries. Dynamic recrystallization (DRX) of α-Mg occurred during hot deformation via a particle stimulated mechanism, and the almost complete DRX with an average grain size around 1.5 µm was obtained after 12p-ECAP. Moreover, abundant nano-sized acicular and spherical precipitates were dynamically precipitated within α-Mg grains during ECAP. Tensile test results indicated that the maximum strength and ductility were acquired for 12p-ECAP alloy with ultimate tensile strength of 372 MPa and fracture elongation of 8%. The enhanced strength of the alloy could be ascribed to fine DRX grains, ultra-fine Ca-containing particles and dynamically precipitated nano-precipitates, while the improved ductility was mainly due to the refined and homogeneous microstructure, and weak texture with high average Schmid factors. Keywords: Mg-Al-Ca-Mn alloy, Equal channel angular pressing, Dynamic recrystallization, Precipitates, Mechanical property

A comparative study on the microstructural evolutions and mechanical properties of as-cast and as-homogenized Mg-3.5Al-4.5Ca-0.4Mn (wt.%) alloys with different Mg2Ca morphologies during equal channel angular pressing (ECAP) is reported herein. The results showed that while the network Mg2Ca phases in the as-cast alloy were broken into ultrafine particles after multipass ECAP, they were still aggregated at original grain boundary regions. After homogenization, large spherical Mg2Ca particles, which were not refined but distributed uniformly through multipass ECAP, were formed. With an increase in ECAP passes, both aggregated ultrafine Mg2Ca particles and large spherical particles stimulated dynamic recrystallization (DRX). The ultrafine Mg2Ca particles introduced incomplete DRX with a finer α-Mg grain size, whereas the large spherical particles resulted in almost complete DRX with a coarser grain size after 12p-ECAP. Moreover, nano-sized acicular and spherical precipitates were dynamically precipitated during ECAP. Owing to the fine grain size, weak texture, ultrafine Mg2Ca particles, and nano precipitates, the 12p-ECAP cast alloy exhibited a high ultimate tensile strength of 331 MPa and moderate fracture elongation of 7.4%. The ECAPed homogenized alloys showed lower mechanical properties, which could be attributed to preexisting microcracks within Mg2Ca spherical particles that were introduced by homogenization.

Development of strong and ductile lightweight magnesium (Mg) alloys has been the subject of enormous research breakthroughs since 2000. This review describes the most significant progress on the design and processing of high-strength wrought Mg alloys containing long-period stacking order (LPSO) phases. It first focuses on the typical atomic structure, transformation, and morphology of various LPSO phases, then explores the key contributions of thermomechanical processing techniques to the metallurgical structure, morphology, spatial dimension, and distribution of diverse LPSO phases and discusses the LPSO-derived strengthening mechanisms of Mg alloys. Finally, future research opportunities for LPSO-containing wrought Mg alloys are proposed on the basis of the mechanistic relationships between the evolution of LPSO phase particles and strengthening mechanisms.

The tension-compression asymmetric mechanical behavior of the AZ91 magnesium alloy with multi-heterogenous microstructure was investigated in comparison with its cast counterpart. The individual effect of different deformation modes in fine and coarse grains are clarified to reveal the underlying mechanism behind the asymmetric yield behavior by electron back-scatter diffraction analysis. The result demonstrated that the mechanical twinning prevailing in coarse grains is responsible for the yield asymmetry of the multi-heterogeneous alloy.

In the present work, we firstly and comparatively investigated the microstructure evolution and mechanical properties of AZ91 alloy processed by equal channel angular pressing (ECAP) combined with prior and post aging treatment. Both processes induce homogenous microstructures consisting of fine grains modified by uniformly dispersed spherical precipitates. The prior aging treatment facilitates a well-developed dynamic recrystallized microstructure with low dislocation density, and finer and more precipitates, while both processes induce comparable grain size. Thus, the prior aging treatment benefits to the occurrence of dynamic recrystallization during subsequent ECAP processing. Furthermore, both the strength and ductility of AZ91 alloy are enhanced and flexibly managed through ECAP with a combination of prior or post aging treatment. The post aging treatment is of benefit to the improvement in yield strength, while the prior aging treatment facilitates the more significant ductility enhancement.

A 0.31 mm-diameter Mg97Y2Zn1 alloy wire with high yield strength of 550 MPa, ultimate tensile strength of 570 MPa and elongation of 12% was successfully prepared via the combination of ECAP and heavy drawing at elevated temperatures. Microstructure observation showed that the 18R phases were broken into fine particles and formed clusters during drawing of ECAP rod. The α-Mg matrix was refined via dynamic recrystallization, and the DRX grains were mixed with dynamically precipitated 14H particles. The ultra-fined microstructure, as well as the homogenous distribution of LPSO particles and clusters, contributed to the exceptional mechanical properties of Mg97Y2Zn1 alloy wire.

In the present work, an up-scaled rotational die equal channel angular pressing (RD-ECAP), which circumvented the limitation of the removing and re-inserting procedure of the conventional ECAP, was developed to make it possible to prepare large scale ECAP billets with dimension of 50 mm × 50 mm × 100 mm, and was successfully applied to an as-cast AZ91 alloy without a prior thermomechanical treatment. Benefiting from the large scale ECAP billet, the anisotropic tensile behavior of the ECAP alloy was examined, and was carefully linked to its microstructure and texture evolution. Our results shown that the large scale AZ91 RD-ECAP alloy exhibited simultaneously improved strength and ductility compared to as-cast alloy, while it possessed significantly anisotropic mechanical behavior. Interestingly, the anisotropy of ductility was nonsignificant, showing dramatically enhanced quasi-isotropic ductility. The improved strength and ductility were ascribed to the significant grain refinement, fine second phase, and texture strengthening. The tensile anisotropy was resulted by the bi-texture which was comprised of four prismatic texture components and three basal texture components. This study clearly highlights the potential for scaling RD-ECAP for an industrial scale implementation, while significant anisotropic mechanic behavior should be paid much attention.

Background Idiopathic pulmonary fibrosis (IPF) is an age-related fatal disease with an unknown etiology. Increased oxidative stress and mitochondrial dysfunction are thought to be involved in its pathogenesis. However, the effect of the AluYb8MUTYH polymorphism on IPF is not known. Results The mean age of onset for IPF in patients homozygous for the AluYb8MUTYH variant (P/P) was 66.5 years old, which was significantly earlier than that in patients with the wild-type (A/A, 70.45 years old). For the 97 male IPF patients with lung function data, the FVC% of the P/P patients was lower than that of the wild-type (A/A) or heterozygous (A/P) patients. The laboratory analysis indicated that an increased mtDNA content and impaired mitochondrial quality control were associated with the P/P genotype. We also confirmed that AluYb8 insertion into MUTYH caused decreased MUTYH1 expression in lung tissues. Methods We compared the lung function of IPF patients and observed the mtDNA content, mtDNA integrity and molecular expression of mitochondrial quality control among subjects with different AluYb8MUTYH genotypes. Additionally, immunoblotting and a reporter gene system were used to test whether altered mitochondrial MUTYH1 expression was linked to AluYb8MUTYH. Conclusions The AluYb8 insertion polymorphism in MUTYH impairs mtDNA stability and affects the age of onset of IPF.

A 0.31 mm-diameter Mg-6 wt% Zn alloy wire with high ultimate tensile strength of 300 MPa and elongation of 11% was successfully prepared via combination of extrusion, ECAP and hot drawing. Its excellent mechanical properties were attributed to the homogeneous and near single-phase microstructure.

Casting magnesium alloys hold the greatest share of magnesium application products due to their short processing period, low cost and near net shape forming. Compared with conventional commercial magnesium alloys or other Mg–RE-based alloys, the novel Mg–RE–TM cast alloys with long period stacking ordered (LPSO) phases usually possess a higher strength and are promising candidates for aluminum alloy applications. Up to now, two ways: alloying design and casting process control (including subsequent heat treatments), have been predominantly employed to further improve the mechanical properties of these alloys. Alloying with other elements or ceramic particles could alter the solidification pattern of alloys, change the morphology of LPSO phases and refine the microstructures. Different casting techniques (conventional casting, rapidly solidification, directional solidification, etc.) introduce various microstructure characteristics, such as dendritic structure, nanocrystalline, metastable phase, anisotropy. Further heat treatments could activate the transformation of various LPSO structures and precipitation of diverse precipitates. All these evolutions exert great impacts on the mechanical properties of the LPSO-containing alloys. However, the underlying mechanisms still remain a subject of debate. Therefore, this review mainly provides the state of the art of the casting magnesium alloys research and the accompanying challenges and summarizes some topics that merit future investigation for developing high-performance Mg–RE–TM cast alloys.

The tendency of AA3003 towards localized corrosion is one of the most challenging issues for its broader use. Intermetallic phases (IMPs) in AA3003 play dual contradictory roles: strengthening effect and initiating pitting. Solving this contradiction contributes to improvement of corrosion resistance and fully utilizing the potential of materials. Herein, a superhydrophobic surface with IMPs in-situ pinning effect was fabricated via a chemical etching approach combined with stearic acid (STA) modification. Thus, IMPs can provide sound support for the superhydrophobic surface and meanwhile eliminate the adverse effect of promoting localized corrosion. Formation mechanism of etching structure was attributed to the synchronous chemical reaction of IMPs and matrix phases in the etchant. Further modification with STA changed mico/nano hierarchical surface from hydrophilicity to superhydrophobicity. The as-prepared surface exhibited a maximum static contact angle of ~169° and a sliding angle of ~1°, possessing excellent superhydrophobicity. Besides, the wettability, self-cleaning, chemical stability, mechanical durability, and corrosion resistance properties of the superhydrophobic surface were comprehensively investigated. The results showed that the corrosion inhibition efficiency exceeded 99% in 3.5 wt% NaCl solution. The pinning direction of IMPs in superhydrophobic surface influenced its properties. It is anticipated that the construction of superhydrophobic surfaces will broaden its promising applications.

The microstructure design based on the development of heterostructure provides a new way for high strength and ductility Mg alloys. However, the wear property, as an important service performance, of Mg alloys with heterostructure is scarcely investigated. In this work, a high strength and ductility AZ91 Mg alloy with multiheterostructure was prepared via a processing route combined industrial-scale equal channel angular pressing (ECAP) and aging. The multiheterostructure consists of the heterogeneous grain structure and heterogeneous precipitates. The dry sliding wear behavior of this multiheterostructured (MH) alloy is investigated compared to the as-cast alloy. The impacts of the applied load and duration time on the wear volume and coefficient of friction (COF) are analyzed, and the wear mechanism is further discussed. The result indicates that although the MH alloy exhibits high-desirable strength-ductility synergy, it shows a poorer wear resistance but a relatively lower COF compared to the as-cast alloy at the present condition. The wear mechanism of both alloys mainly involves abrasive wear, as well as mild adhesion, delamination, and oxidation. In comparison, the MH alloy shows relatively severe adhesion, delamination, and oxidation. The poor wear resistance of the MH alloy at the present dry sliding wear condition is linked to the abundant grain boundaries and fine precipitates. Therefore, one should reasonably use the MH Mg alloy considering the service conditions to seek advantages and avoid disadvantages.

This work analyzes the effects of ultrafine aluminum (Al) grains on the anodizing coating reaction and anticorrosion performance of anodized industrial pure Al. Equal-channel angular pressing (ECAP) was applied to cast pure Al continuously for 16 passes at room temperature, and its average grain size was dramatically refined to about 1.5 &mu, m. The ultrafine-grain (UFG) pure Al was further anodized with a cast sample via a parallel anodizing circuit at a constant total input current. Benefited by the higher volume fraction of grain boundaries and higher internal energy of the UFG substrate, the anodizing process of the ECAP-processed pure Al was significantly accelerated, showing a more intense initial anodizing reaction, a faster initial coating thickening, and much earlier porous-layer formation compared to the cast sample. As the anodizing reaction continued, the newly formed thicker coating of the ECAP-coated sample significantly hindered the diffusion process, weakening the thermodynamic advantage and decreasing the anodizing current of the ECAP-processed sample. During the entire anodizing duration, the ECAP-processed pure Al experienced gradually decreased anodizing current, while the cast sample experienced increased anodizing current. Because of the more total reaction, the ECAP-coated sample always maintained a relatively thicker coating and better anticorrosion performance during the entire anodizing duration.

The isothermal oxidation behavior of 17Cr-0.85Si-0.5Nb-1.2Cu ferritic stainless steel in air was studied from 850°C to 1050°C by analyzing its weight gain after oxidation. The kinetic curves were plotted using the oxidation weight-gain data, and the structure, surface morphology, and element distribution of the oxide films were analyzed by XRD, SEM, and EDS. The results showed that the oxidation kinetics curves at 850°C and 950°C followed a parabolic law, and a continuous and dense oxide film composed of Cr2O3 and MnCr2O4, FeCr2O4, and Cu-Cr rich spinel was formed, which reveals that the steel displayed good oxidation resistance. When the temperature was increased to 1050°C, the oxidation kinetics curves gradually changed from parabolic to linear after 40 h exposure, which indicated that the oxidation resistance significantly worsened. A lower oxidation resistance was observed at 1050°C due to the formation of a large amount of Fe2O3 on the surface and the volatilization of the inner Cr2O3 layer.

The influence of temperature and strain rate on the hot tensile properties of 0Cr18AlSi ferritic stainless steel, a potential structural material in the ultra-supercritical generation industry, was investigated at temperatures ranging from 873 to 1123 K and strain rates of 1.7 &times, 10&minus, 4&ndash, 1.7 &times, 2 s&minus, 1. The microstructural evolution linked to the hot deformation mechanism was characterized by electron backscatter diffraction (EBSD). At the same strain rate, the yield strength and ultimate tensile strength decrease rapidly from 873 K to 1023 K and then gradually to 1123 K. Meanwhile, both yield strength and ultimate tensile strength increase with the increase in strain rate. At high temperatures and low strain rates, the prolonged necking deformation can be observed, which determines the ductility of the steel to some extent. The maximum elongation is obtained at 1023 K for the strain rates of 1.7 &times, 3 and 1.7 &times, 1, while this temperature is postponed to 1073 K once decreasing the strain rate to 1.7 &times, 4 s&minus, 1. Dynamic recovery (DRV) and continuous dynamic recrystallization (CDRX) are found to be the main softening mechanisms during the hot tensile deformation. With the increase of temperature and the decrease of strain rate (i.e., 1123 K and 1.7 &times, 1), the sub-grain coalescence becomes the main mode of CDRX that evolved from the sub-grain rotation. The gradual decrease in strength above 1023 K is related to the limited increase of dynamic recrystallization and the sufficient DRV. The area around the new small recrystallized grains on the coarse grain boundaries provides the nucleation site for cavity, which generally results in a reduction in ductility. Constitutive analysis shows that the stress exponent and the deformation activation energy are 5.9 and 355 kJ&middot, mol&minus, 1 respectively, indicating that the dominant deformation mechanism is the dislocations motion controlled by climb. This work makes a deeply understanding of the hot deformation behavior and its mechanism of the Al-bearing ferritic stainless steel and thus provides a basal design consideration for its extensive application.

Magnesium alloys are considered for building materials in this study due to their natural immunity to corrosion in alkaline concrete pore solution. But, chloride ions attack often hinders the application of most metals. Therefore, it is necessary to conduct a preliminary corrosion evaluation and attempt to find an effective way to resist the attack of chloride ions in concrete pore solution. In our study, hydrothermal treatment is carried out to modify Mg-9.3 wt. % Al alloy. After the treatment in NaOH solution for 10 h, scanning electron microscopy (SEM) reveals that a layer of dense coating with a thickness of about 5 μm is formed on Mg alloy. Energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray Diffraction (XRD) are combined to analyze the coating, and it is thereby confirmed that the coating is mainly composed of Mg(OH)2. As expected, both immersion test and electrochemical corrosion test show that the coated magnesium alloy has a better corrosion resistance than the uncoated one in simulated concrete pore solution with and without chloride ions. In summary, it indicates that hydrothermal treatment is a feasible method to improve the corrosion resistance of Mg alloys used for building engineering from the perspective of corrosion science.

An equal channel angular pressing (ECAP) process is used to obtain a fine-grain magnesium-gadolinium-silver alloy, and hierarchical precipitates embedded in the fine-grain matrix are achieved by subsequent peak-aging. These hierarchical precipitates are composed of the β phase sub-microparticles, β phase nanoparticles, γ" phase nanoplates, and β' phase nanoplates. They facilitate corrosion in the 3.5 wt% NaCl solution to some extent due to micro-galvanic corrosion. However, compared to those precipitates in the as-cast alloy, the spatial redistribution of the hierarchical precipitates improves the corrosion resistance of the material, which is possibly attributed to the formation of a protective corrosion product film.

Microcystin-LR (MC-LR) is the most abundant toxicant among microcystin variants produced by cyanobacteria. MC-induced toxicity is broadly reported to pose a threat to aquatic animals and humans and has been associated with the dysfunction of some organs such as liver and kidney. However, MC-induced neurotoxicity has not been well characterized after long-term exposure. This study was designed to investigate the neurotoxic effects after chronic oral administration of MC-LR. In our trial, C57/BL6 mice received MC-LR at 0, 1, 5, 10, 20 and 40 μg/L in drinking water for twelve months. Our data demonstrated that mitochondrial DNA (mtDNA) damage was evident in the damaged neurons as a result of chronic exposure. Histopathological abnormalities and mtDNA damage were observed in the hippocampus and cerebral cortex. Furthermore, MC-LR exerted distinct effects on these two brain regions. The hippocampus was more susceptible to the treatment of MC-LR compared with the cerebral cortex. However, no strong relationships were observed between the genotoxic effects and exposure doses. In conclusion, this study has provided a mtDNA-related mechanism for underlying chronic neurotoxicity of MC-LR and suggested the presence of differential toxicant effects on the hippocampus and cerebral cortex.

A chessboard-like microstructured AZ91 alloy with multi-heterogenous structures was prepared via a combined processing method of high temperature ECAP and short-time aging. The ECAP-aged alloy exhibited superior mechanical properties with ultimate tensile strength of 406 MPa and elongation to failure of 17.9%.

Yellow ceramic coatings were prepared on ultra-fine grained (UFG) AZ91 magnesium alloy using micro-arc oxidation (MAO) process in the alkaline-silicate electrolyte with different KMnO4 addition. Microstructure and phase composition were investigated by SEM, EDS (energy-dispersive spectrometer) and XRD (X-ray diffraction). With 2 gL−1 KMnO4 addition, the extreme sparking discharge was inhibited and the coating exhibited more compact and uniform morphology. However, adding 3 gL−1 KMnO4 in electrolyte extremely woke the discharge intensity and caused deleterious influence such as micro-crack. The generation of complex oxide Mg6MnO8 phase resulted in the yellow colour of the coatings. Electrochemical measurements including potentiodynamic polarisation and electrochemical impedance spectroscopy tests were carried out in 3.5% NaCl solution. The UFG alloy with the MAO coating produced with 2 gL−1 KMnO4 addition exhibited superior corrosion resistance, which was owing to the more compact and uniform micro...

The effect of water film on the nanoscratching behavior of monocrystalline Cu was studied by molecular dynamics (MD) simulation. The results indicate that the friction force acting on abrasive particle increases due to the resistance of water film accumulating ahead of particle, but the water film with lubrication decreases friction force acting on Cu surface. The accumulation of water molecules around particle causes the anisotropy of ridge and the surface damage around the groove, and the water molecules remaining in the groove lead to the non-regular groove structure. The dislocation evolution displays the re-organization of the dislocation network in the nanoscratching process. The evaluation of removal efficiency shows the number of removed Cu atoms decreases with water film thickness. It is considered that an appropriate rather than a high removal efficiency should be adopted to evaluate the polishing process in real (chemical mechanical polishing) CMP. These results are helpful to reveal the polishing mechanism under the effect of water film from physical perspective, which benefits the development of ultra-precision manufacture and miniaturized components, as well as the innovation of CMP technology.

The pop-in events and the deformation mechanisms of (1 1 1) Si under spherical nanoindentation were investigated using molecular dynamics simulations. The simulations result successfully reproduced the plastic deformation mediated by high-pressure phase transformations and dislocation burst, and the highly desirable brittle fracture of silicon. Quadruple occurrences of the pop-ins were observed in loading curves. The one-to-one relationship between the multiple pop-ins and the deformation mechanisms was established. Two fundamental processes, the asynchronous occurrences of high-pressure phase transformation and extrusion of α-Si, were identified from several deformation modes to be responsible for the multiple pop-ins. Moreover, the dislocation burst also contributes to the plastic deformation, and the cracks were observed to contribute to the brittle deformation, but contribute nothing to the pop-ins.

A fundamental understanding of the mechanical properties and deformation behaviors of surface modified silicon during chemical mechanical polishing (CMP) processes is difficult to obtain at the nanometer scale. In this research, MD simulations of monocrystalline silicon covered with an amorphous SiO2 film with different thickness are implemented by nanoindentation, and it is found that both the indentation modulus and hardness increase with the growing indentation depth owning to the strongly silicon substrate effect. At the same indentation depth, the indentation modulus decreases shapely with the increase of film thickness because of less substrate influence, while the hardness agrees well with the trend of modulus at shallow depth but mismatches at larger indentation depth. The observed SiO2 film deformation consists of densification and thinning along indentation direction and extension in the deformed area due to the rotation and deformation of massive SiO4 tetrahedra. The SiO2 film plays an important role in the onset and development of silicon phase transformation. The thinner the SiO2 film is, the earlier the silicon phase transformation takes place. So the numbers of phase transformation atoms increase with the decrease of SiO2 film thickness at the same indentation depth. It is suggested that the thicker film should be better during CMP process for higher material removal rate and less defects within silicon substrate.

We report a strategy of gradient heterogeneous structure (GHS) architecture to achieve a superior strength-ductility combination in additively manufactured (AM) 316L stainless steel prepared by selective laser melting (SLM) and ultrasonic severe surface rolling (USSR). The GHS is a microstructure gradient system, which is composed of a gradient structured outer layer and a hierarchically heterostructured interlayer. The gradient structured outer layer exhibits a variation in grain size, phases, dislocations, twins, and cellular structure with depth and has a large thickness of approximately 1000 µm. The average grain size is approximately 93.9 nm in the topmost surface layer and increases with increasing depth from the treated surface. The hierarchically heterostructured interlayer has the heterogeneous grain structure, cellular structure, high-density dislocations, and nanoprecipitates, with length scales spanning several orders of magnitude. Due to the high microstructural heterogeneity arising from the combination of two types of heterogeneous structures, the GHS strengthens the synergistic effect, and thus results 316L stainless steel with a superior strength and high ductility. Furthermore, the mechanical properties of the GHS 316L stainless steel can be tuned by tailoring the microstructure: the larger the volume fraction of the gradient structured outer layer is, the higher the strength, but the lower the ductility. Molecular dynamics simulations indicate that deformation twinning, in addition to dislocation slipping, is an important deformation mechanism for nanocrystalline 316L samples at a large strain and thus plays an important role in maintaining strain hardening and ductility. We also discuss the potential application of USSR to AM parts to improve their mechanical properties and surface integrity. Our work demonstrates the potential of the proposed highly heterogeneous microstructure design strategy to prepare high-performance AM parts.

This paper reports the whispering gallery mode (WGM) splitting behavior as-observed between pairs of size-matched microspheres with tight-binding positions. Dye-doped microspheres were excited by pulsed lasers in order that the WGM laser spectra could be monitored. Via analysis of experimental results, we investigated the effects of spacing between two coupled microspheres on coupling strength, and found that coupling strength was increased with decreasing spacing between the microspheres through mode splitting spectra. We demonstrated the effects of environment refractive index (RI) of coupling spot on mode splitting spectra through dripping liquid on the slit of the bi-spheres, and observed that coupling strength changes with the influence of RI. Furthermore, temperature-dependent experiments showed that temperature change will not disturb the mode splitting behavior, this structure exhibits potential for self-referencing sensing.

In the present study, the evolution and strengthening effect of precipitates in 17Cr ferrite stainless steel during the creep process are investigated. The precipitates are characterized by scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. Moreover, the interactions between the precipitates and the grain boundary and dislocation are quantitatively analysed. The results show that Cu- and Nb-rich phases are formed during the creep process. The stress concentration at the tip of the precipitates, the stacking fault at the precipitate edge and the internal dislocation can promote the nucleation of the Nb-rich phase. The Nb-rich precipitates can provide the driving force for the nucleation of Cu-rich particles through stacking fault, dislocation entanglement and internal dislocation. At 700 °C, as the creep time increases, the pinning effect of precipitates on the grain boundary increases linearly, while the pinning effect on the dislocation decreases. As the creep temperature increases, a peak pinning effect on the grain boundary is observed at 750 °C, and the pinning effect of the precipitates on dislocation decreases gradually inside the grain. The formation of dislocation networks at grain boundaries can delay pinning effect reduction of the Nb-rich phase, and the main blocking mechanism of precipitates on dislocation movement is bypassing. The precipitation strengthening effects of Cu- and Nb-rich phases are also compared with each other.

Mg–Gd–Ag-based alloys have attracted considerable attention in recent years owing to their high strength. However, their characteristic mechanical behavior remains unclear. Herein, the tensile anisotropy, tension–compression asymmetry, and strain-hardening behavior of a high-performance Mg–10.6Gd–2Ag (wt%) alloy fabricated by equal-channel angular pressing (ECAP) were systematically investigated and correlated with the evolution of microstructure and texture. The ECAP alloy exhibited synchronously enhanced tensile strength and ductility along all three directions compared with the as-cast alloy as well as improved compressive strength along the extrusion direction (ED) accompanied by slightly decreased ductility. In contrast to the pronounced reversed yield asymmetry for the as-cast alloy, the ECAP alloy exhibited a weak direct yield asymmetry along the ED. After aging, the tensile and compressive yield strengths of the ECAP alloy increased to 409 and 402 MPa, respectively, owing to the coprecipitation of basal γ'' and prismatic β' nanoplates, manifesting a near-symmetric yield response. Moreover, two strain-hardening stages (stage I and stage III) were detected in tensile deformation for all the investigated alloys, while all three stages were observed in compressive deformation. Both the strain-hardening ability and strength in the ECAP alloy before and after aging decreased slightly in the following order: ED > transverse direction (TD) > normal direction (ND), representing low anisotropy. In short, the present ECAP Mg–10.6Gd–2Ag alloy exhibited the advantages of high strength and ductility, near-symmetric yield response, and low anisotropy.

To emphasize the effect of humid or liquid circumstances on the mechanical behavior of metallic thin films with dimensions down to the nanoscale, atomistic simulations were employed to study the water film affecting the plastic deformation of Cu thin film during nanoindentation with different loading rates and indentation speeds. The results indicate that the largest load increases with the water film thickness and indentation rate for displacement-controlled indentation, contrary to the trend of the largest penetration depth for load-controlled indentation. The dislocation evolution reveals that the raised indentation speed or loading rate results in larger and rapider plastic deformation. The presence and thickening of water film as a media of force transmission from indenter to Cu thin film lead to a wide range of plasticity within Cu, large load dissipation and surface damage. The plastic deformation of Cu thin film under different indentation modes shows similarly changed trend. Our observations provide a better understanding of the mechanism of plastic deformation under the effect of water film.

ATP-binding cassette A3 (ABCA3) is a phospholipid carrier that is mainly expressed in the alveolar epithelium. Biallelic mutations of ABCA3 has been associated with fatal respiratory distress syndrome and interstitial lung disease (ILD) in children. However, whether variations in ABCA3 have a role in the development of adult ILD, including idiopathic pulmonary fibrosis (IPF), remains to be addressed. In this study, we screened for germline variants of ABCA3 by exons-sequencing in 30 patients with sporadic IPF and in 30 matched healthy controls. Eleven missense variants, predominantly in heterozygous, were found in 13 of these patients, but only two missenses in 2 healthy controls. We then selected four of the detected missense variants (p.L39V, p.S828F, p.V968M and p.G1205R) to performed cohort analysis in 1,024 ILD patients, containing 250 IPF and 774 connective tissue disease-ILD (CTD-ILD) patients, and 1,054 healthy individuals. Our results showed that the allele frequency of p.G1205R, but not p.L39V, was significantly higher in ILD patients than in healthy controls. However, no additional subject carrying the variant p.S828F or p.V968M was detected in the cohort analysis. These results indicate that the heterozygous ABCA3 gene variants may contribute to susceptibility to diseases in the Chinese population.

Large-scale molecular dynamics simulations of nanoindentation on a (100) oriented silicon surface were performed to investigate the mechanical behavior and phase transformation of single crystalline silicon. The direct crystalline-to-amorphous transformation is observed during the nanoindentation with a spherical indenter as long as the applied indentation strain or load is large enough. This amorphization is accompanied by a distinct discontinuity in the load–indentation strain curves, known as “pop-in”. Herein, we have demonstrated the pressure-induced amorphization processes via direct lattice distortion. Moreover, the combination of large shear stress and associated hydrostatic pressure facilitates this crystalline-to-amorphous transformation. The structural characteristics, phase distribution, and phase transformation path have also been discussed in this study. The present results provide a new insight into the mechanical behavior and phase transformation of monocrystalline silicon.

The microstructural evolution of a 18R single phase (S18) alloy during annealing at 773 K for 100 h was investigated in order to reveal the formation mechanism of 14H phase. The results showed that the as-cast S18 alloy was composed of 18R phase (its volume fraction exceeds 93%), W particles and α –Mg phase. The 18R phase in S18 alloy was thermally stable and was not transformed into 14H long period stacking ordered (LPSO) phase during annealing. However, 14H lamellas formed within tiny α –Mg slices, and their average size and volume fraction increased with prolonging annealing time. Moreover, the 14H phase is nucleated within α –Mg independently on the basis of basal stacking faults (SFs). The broadening growth of 14H lamellas is an interface-controlled process which involves ledges on basal planes, while the lengthening growth is a diffusion-controlled process and is associated with diffusion of solute atoms. The formation mechanism of 14H phase in this alloy could be explained as α –Mg'→ α –Mg+14H.

In three-body abrasion, the abrasive particle shape has a major impact on the movement patterns. These consist of sliding or rolling relative to the abraded surfaces. It has been recognized that the movement patterns of the particles dominate the wear mechanism of the materials in three-body abrasion. In this paper, the movement patterns of monocrystalline diamond ellipsoidal particles, which are sandwiched between monocrystalline copper workpieces, were investigated by large-scale molecular dynamics (MD). During the simulations, the axial ratio of the ellipsoidal particle varied from 0.90 (an approximate sphere) to 0.50 (a flattened ellipsoid). It has been found that there is a transition of the movement patterns between rolling and sliding. The particle slides when the axial ratio is smaller than 0.83, and it rolls when the axial ratio is larger than 0.83. Normal load and friction force curves were also obtained relative to the wear time. It has been shown that the average friction coefficient of rolling particles is lower than that of sliding particles. If the ratio of two-moment arms, such as the driving and resistant force moment arms of the particle, is defined as e/h, the curves for the friction coefficient and value e/h can determine the movement patterns of particles at the nanoscale, the same as at the macroscale. When the friction coefficient is higher than e/h, rolling of the particle occurs, whereas the particle slides if the friction coefficient is smaller than e/h. By comparing with macroscale three-body abrasion, a particle at the nanoscale has a strong tendency to roll because of its significant elastic recovery. When the particle rolls, the defect depth, groove depth and dislocation length are all increased relative to particle sliding, resulting in more severe subsurface defects of the monocrystalline copper.

Silicon undergoes a brittle-to-ductile transition as its characteristic dimension reduces from macroscale to nanoscale. The thorough understanding of the plastic deformation mechanism of silicon at the nanoscale is still challenging, although it is essential for developing Si-based micro/nanoelectromechanical systems (MEMS/NEMS). Given the wide application of silicon in extreme conditions, it is, therefore, highly desirable to reveal the nanomechanical behavior of silicon from cryogenic temperature to elevated temperature. In this paper, large-scale molecular dynamics (MD) simulations were performed to reveal the spherical nanoindentation response and plastic deformation mechanism of (110)Si at the temperature range of 0.5 K to 573 K. Special attention was paid to the effect of temperature. Multiple pop-ins detected in load/pressure-indentation strain curves are impacted by temperature. Four featured structures induced by nanoindentation, including high-pressure phases, extrusion of &alpha, Si, dislocations, and crack, are observed at all temperatures, consistent with experiment results. The detailed structure evolution of silicon was revealed at the atomic scale and its dependence on temperature was analyzed. Furthermore, structure changes were correlated with pop-ins in load/pressure-indentation strain curves. These results may advance our understanding of the mechanical properties of silicon.

In this paper, the effect of the equal-channel-angular-pressed (ECAPed) substrate on the coating formation and anticorrosion performance of the anodized Al&ndash, 11Si alloy was systematically investigated. The ECAP process dramatically refines both Al and Si phases of the alloy. The parallel anodizing circuit is designed to enable a comparative study of anodizing process between the cast and the ECAPed alloys by tracking their respective anodizing current quota. The optimum coatings of both alloys were obtained after anodization for 30 min. The ECAPed alloy attained a thicker, more compact, and more uniform coating. Energetic crystal defects in the fine Al grains of the ECAPed substrate promote the anodizing reaction and lead to the thicker coating. Fragmented and uniformly distributed fine Si particles in the ECAPed alloy effectively suppress the coating cracks, enhancing the compactness of the coating. Overall, the ECAP-coated sample exhibits the best anticorrosion performance, which is evidenced by the concurrently enhanced prevention of coating and improved corrosion resistance of the substrate.

Naturally exposed rusted rebar has been widely used for the production of reinforced concrete. However, rusted rebar is prone to corrosion under chloride ion (Cl&minus, ) contamination and/or at a low alkalinity of concrete. This study employed two surface modification methods, sand blasting and wire brushing, to augment the corrosion resistance of naturally exposed rusted rebar. Electrochemical tests revealed that the surface-modified rebar displayed a significant improvement of passivation in the concrete alkaline environment and anticorrosion performance in both the Cl&minus, free and Cl&minus, containing simulated concrete pore solutions of different alkalinity. The enhanced performance was mainly due to the elimination of the rust layer and the direct exposure of the fresh metallic surface to the alkaline medium. Moreover, the effect of surface nanograins on the intensified passive film led to the best passivation performance of the wire-brushed rebar. The overall findings demonstrate that the two developed methods were conducive to the passivation and anticorrosion performance of the rusted rebar and thereby hold great promise for improving the service life of the reinforced concrete structures.

Cast Mg-9Li alloy was successfully solid-solution (SS) treated via heating at 575 &deg, C for 4.5 h and rapidly quenched with ice-water mixture. The mechanical property and corrosion resistance of the SS alloy were simultaneously improved. Rapid bcc/hcp phase transition of the alloy occurred during the quenching process, creating the newly precipitated needle-like fine &alpha, Mg phase, uniformly distributed in the &beta, Li phase matrix. Dramatic grain refinement and uniform distribution of the &alpha, Mg phase, as well as the massively increased &alpha, /&beta, phase interfaces, are factors leading to the improved mechanical property of the SS alloy. Meanwhile, due to the modified duplex-phase structure, the SS alloy has a uniform corrosion-resistant surface film on the &beta, Li phase, which completely covers the entire alloy surface and efficiently protects the substrate. In addition, the SS alloy has fewer difference in the elements concentration and corrosion activity of the duplex phases, which reduces the pitting sensitivity and improves the corrosion resistance of the alloy matrix. The findings in this binary Mg-Li alloy can also serve as a benchmark for other more practical and complicated Mg-Li alloys.

The low hardness and poor wear resistance of AISI 316 L austenitic stainless-steel sabotage its outer appearance and shorten its service life when it is subjected to sliding. In this paper, the single-pass ultrasonic surface rolling (USR) process was used to modify the surface of 316 L austenitic stainless steel. A nanostructured surface layer with a depth span of 15 &mu, m was fabricated. Dry wear tests of USR samples were performed on a ring-on-block tester at room temperature, and the results were compared with those for the as-received sample. The USR sample showed a significant reduction in wear mass loss and an improved hardness, as well as a decreased surface roughness. The detailed wear mechanism was also investigated by SEM observations of the worn surfaces. It was indicated that oxidation and abrasive wear, accompanied by mild adhesion, dominated the wear of USR 316 L stainless steel at both low and high speeds. The superior wear performance of USR 316 L was attributed to its nanostructured surface layer, which was characterized by a high hardness and thereby suppressed the severe abrasive wear. The results provided an alternative approach to modifying the surface of 316 L stainless steel, without changing its surface chemical components.