In this study, gradient nanocrystallization and enhanced surface mechanical properties in commercial pure titanium, which were induced by an electropulsing-assisted ultrasonic surface rolling process ...(EP-USRP), were systematically investigated. The results indicated that EP-USRP at an optimum frequency of 500Hz is advantageous over a conventional ultrasonic surface rolling process (USRP) in achieving excellent surface mechanical properties, including a lower friction coefficient and less wear loss (maximum depth of wear scar decreased to two-thirds of that of USRP). Such enhancements may be attributed to a higher surface maximum hardness (308 HV, increased by 46.7% compared to the turning sample), deeper severe plastic deformation layer (480μm, ~0.5 times greater than that of USRP), smaller surface roughness (Ra 0.026μm), and higher compressive residual stresses. There is a balance between electropulsing-induced ductility and ultrasonic impact-induced work hardening. At the optimum conditions, the mobility of immobile dislocations is remarkably improved owing to the thermal and athermal effects of electropulsing as well as the ultrasonic vibration energy from USRP, leading to higher strains and dislocation densities; these induce further dynamic recrystallization in the sub-grains until a new balance is reached.
Electropulsing assisted ultrasonic surface rolling process (EP-USRP) is advantageous over traditional ultrasonic surface rolling process (USRP) to receive excellent surface mechanical properties and nanocrystallization by promoting the mobility of immobile dislocations. Display omitted
•Electropulsing coupled with the traditional ultrasonic surface rolling process (USRP) was applied on commercial pure titanium.•Surface mechanical properties were remarkably enhanced by electropulsing-assisted ultrasonic surface rolling (EP-USRP).•The enhanced surface mechanical properties are attributed to the formation of nanocrystallites with high strength and ductility.•The application of electropulsing during USRP promotes nanocrystallization due to the accelerated mobility of immobile dislocations.
AZ31 Mg and Mg-1Gd alloys were subjected to electroplastic rolling (ER) and electroplastic-asymmetric rolling (EASR). Due to the additional shear stress in EASR, different deformation behaviors, ...including twinning, dislocations and DRX, were witnessed in EASR. For AZ31, significant grain refinement was achieved in the EASR sample. The refined grains with weakened texture contributed to the largely enhanced tensile ductility of the EASR sample. While for Mg-1Gd, the formation of extension twins was booming and propagated throughout the EASR sample, which was considered to be attributed to the high participation of non-basal slip during deformation. Extension twins and their related recrystallization strongly influenced the texture evolution and mechanical properties of the EASR sample, so that both the tensile ductility and strength of the EASR sample were improved.
•Nanoporous TiO2-based composite films are fabricated via hybrid anodization.•Films form by concurrent Ti anodization and electrophoretic SnO2/MoO3 deposition.•The inclusion of SnO2 or MoO3 enhance ...the discharge capacity for ~5 and ~3 fold.•Enhancement is due to improved charge-transfer and Li+ transfer paths.•A self-modification effect of TiO2-based films upon cycling is firstly reported.
Although modification with SnO2 or MoO3 is known to improve the properties of TiO2-based anode materials for lithium-ion batteries (LIBs), simple fabrication methods are required to realize practical applications. Herein, we report a novel approach to fabricate SnO2- or MoO3-modified nanoporous TiO2–TiO–TiN composite films by a hybrid anodization process in nitric-based aqueous solutions containing SnO32− or Mo7O246− ions. Concurrent anodic reactions resulted in Ti anodization to produce a composite film and the electrophoretic deposition of SnO2 or MoO3 colloids in the nanopores of the matrix film. Both TiO2–TiO–TiN@SnO2 and TiO2–TiO–TiN@MoO3 composite films exhibited enhanced discharge capacities (~5- and 3-fold higher than that of the bare matrix film). This enhanced performance was attributed to the synergic effect of improved charge-transfer and additional capacity by depositing nanocrystalline SnO2 and MoO3 nanoparticles in the TiO2–TiO–TiN films, and the presence of nanoporous structures, which provided suitable Li+ transfer paths and reaction sites. The hybridization of nanoporous TiO2 films with SnO2 and MoO3 nanoparticles can simultaneously enhance the discharge capacity and address structural degradation issues in Sn- and MoO3-based electrodes. This simple hybrid anodization approach provides a promising strategy for designing high-power-density and high-safety anode materials for future LIBs.
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The effect of electropulsing-assisted ultrasonic nanocrystalline surface modification (EP-UNSM) on surface mechanical properties and microstructure of Ti-6Al-4V alloy is investigated. Compared to ...conventional ultrasonic nanocrystalline surface modification (UNSM), EP-UNSM can effectively facilitate surface roughness and morphology, leading to excellent surface roughness (reduced from Ra 0.918 to Ra 0.028 μm by UNSM and Ra 0.019 μm by EP-UNSM) and smoother morphology with less cracks and defects. Surface friction coefficients are enhanced, resulting in lower and smoother friction coefficients. In addition, the surface-strengthened layer and ultra-refined grains are significantly enhanced with more severe plastic deformation and a greater surface hardness (a maximum hardness value of 407 HV and an effective depth of 550 μm, in comparison with the maximum hardness value of 364 HV and effective depth of 300 μm obtained by conventional UNSM). Remarkable enhancement of surface mechanical properties can be attributed to the refined gradient microstructure and the enhanced severe plastic deformation layer induced by coupling the effects of UNSM and electropulsing. The accelerated dislocation mobility and atom diffusion caused by the thermal and athermal effects of electropulsing treatment may be the primary intrinsic reasons for these improvements.
Experiments were designed to compare the rollability of magnesium alloy AZ31 sheet in two rolling schedules at the same rolling temperatures: multi-pass electroplastic rolling (ER) and warm rolling ...(WR). While cracks occur in WR sheet at an accumulative true strain of -0.24, the sheet can be rolled by ER up to an accumulative true strain of -1.09 without edge-cracking. This rollability enhancement in ER sheet was found to be related to the improved homogeneity of plastic deformation and dynamic recrystallization (DRX), which postpones the crack initiation. A 'twinning - shear banding - DRX' microstructure evolution model was proposed to explain the effect of pulsed electric current on the homogeneity of deformation and subsequent DRX. The use of ER sheet could pave the way for low-cost applications of lightweight magnesium components.
We report the fabrication of self-lubricating nanoporous anodic titania films through spark anodization in an aqueous ammonia sulfate electrolyte on a hardened nanocrystalline layer of Ti-6Al-4V rods ...after electropulse-assisted ultrasonic surface rolling process (EP-USRP). The spark anodization with an optimum anodizing voltage of 130 V produced sponge-like nanoporous anodic titania films with stable crystalline structure of rutile-phase TiO
2
, and the EP-USRP resulted in a nanocrystalline layer with a higher surface hardening depth (> 220 µm) through severe plastic deformation. The combinatorial technique resulted in excellent tribological properties, with lower friction coefficient of ~ 0.72 (compared to EP-USRP of ~ 0.80), smoother wear scar with less adhesion and less wear loss (maximum depth of 12 nm, 33.3% lower than the EP-USRP sample). These enhancements are attributed to the synergetic effect of the self-lubricating nanoporous anodic titania films formed by spark anodization (which acted as transition layer and prevented direct contact between the counter materials and the substrate) and the hardened nanocrystalline layer formed by EP-USRP (which slowed down the consumption of the anodic powder).
This article has been retracted at the request of < This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).
This article ...has been retracted at the request of the Editor-in-Chief.
Figure 2 duplicates Figure 8 and Figure 3 duplicates Figure 9 of the paper published by the authors in the Journal of the Mechanical Behavior of Biomedical Materials 40 (2014) 287–296 http://dx.doi.org/10.1016/j.jmbbm.2014.08.022.
One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents an abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.
Journal records indicate that confirmation of the submission and publication of the article was sent to the first author's email address and the individual listed as the corresponding author did not receive any correspondence from the journal throughout the submission process. >.
This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).
This article has been retracted at the request of the ...Editor-in-Chief.
The authors have reused figures and text that have already appeared in their previous articles. Figure 6a duplicates figure 6a (horizontally flipped) in Reference 1, while figure 6c duplicates figure 6c in Reference 1 and figure 3c in Reference 2 (albeit different scale is reported for each of these three figures). Figure 7 duplicates panels from figure 9 in Reference 3.
The article also duplicates parts of the text that appeared in Reference 1.
One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents an abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.
Journal records indicate that confirmation of the submission and publication of the article was sent to the first author’s email address but not to the corresponding author's email address.
References
1 Surf Coat Tech 258 (2014) 467-484, http://dx.doi.org/10.1016/j.surfcoat.2014.08.052.
2 J Alloys Compd 616 (2014) 173-183, http://dx.doi.org/10.1016/j.jallcom.2014.07.143.
3 J Mater Res 29 (2014) 1500-1512, http://dx.doi.org/10.1557/jmr.2014.171.
The effect of coupling process of high-energy electropulsing treatment and high-frequency ultrasonic striking treatment on the mechanical properties and microstructure evolution of biomedical ...Ti-6Al-4V alloy is investigated. Results show that the materials ductility under electropulsing treatment is noticeably improved while sacrificing the strength slightly. In this process, refined microstructure is obtained, accompanying by recrystallization process and weakened basal texture. Rapid improvement of microstructure and ductility in low temperature is attributed to accelerated atoms diffusion in recrystallization process with the coupling of thermal and athermal effects. Materials surface microhardness is dramatically enhanced by ultrasonic striking treatment and grain size reaches more than twice of original state. Plastic strain and phase change in the surface layer is contributed in ultrasonic surface strengthening effect.
Experiments were designed to compare the rollability of magnesium alloy AZ31 sheet in two rolling schedules at the same rolling temperatures: multi-pass electroplastic rolling (ER) and warm rolling ...(WR). While cracks occur in WR sheet at an accumulative true strain of −0.24, the sheet can be rolled by ER up to an accumulative true strain of −1.09 without edge-cracking. This rollability enhancement in ER sheet was found to be related to the improved homogeneity of plastic deformation and dynamic recrystallization (DRX), which postpones the crack initiation. A ‘twinning - shear banding - DRX’ microstructure evolution model was proposed to explain the effect of pulsed electric current on the homogeneity of deformation and subsequent DRX. The use of ER sheet could pave the way for low-cost applications of lightweight magnesium components.
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•AZ31 sheet by electroplastic rolling exhibits significantly better rollability than that of conventional warm rolling.•The enhanced rollability in electroplastic rolled sheet is due to the improved homogeneity of deformation and DRX.•The improved homogeneity of deformation and DRX is related to the athermal effect of the pulsed electric current.
