Titanium materials are ideal targets for selective laser melting (SLM), because they are expensive and difficult to machinery using traditional technologies. After briefly introducing the SLM process ...and processing factors involved, this paper reviews the recent progresses in SLM of titanium alloys and their composites for biomedical applications, especially developing new titanium powder for SLM. Although the current feedstock titanium powder for SLM is limited to CP‐Ti, Ti–6Al–4V, and Ti–6Al–7Nb, this review extends attractive progresses in the SLM of all types of titanium, composites, and porous structures including Ti–24Nb–4Zr–8Sn and Ti–TiB/TiC composites with focus on the manufacture by SLM and resulting unique microstructure and properties (mechanical, wear/corrosion resistance properties).
Titanium materials are ideal targets for selective laser melting (SLM), because they are expensive and difficult to machinery, using traditional technologies. This review extends attractive progresses in SLM of all types of titanium, their composites and porous structures, with focus on the manufacture by SLM and the resulting microstructure and properties and the development of new alloy powder materials. The SLM process and factors involved are also briefly reviewed.
Compared with stainless steel and Co–Cr‐based alloys, Ti and its alloys are widely used as biomedical implants due to many fascinating properties, such as superior mechanical properties, strong ...corrosion resistance, and excellent biocompatibility. After briefly introducing several most commonly used biomedical materials, this article reviews the recent development in Ti alloys and their biomedical applications, especially the low‐modulus β‐type Ti alloys and their design methods. This review also systemically investigates the recently attractive progress in preparation of biomedical Ti alloys, including additive manufacturing, porous powder metallurgy, and severe plastic deformation, applied in the manufacturing and the influenced microstructures and properties. Nevertheless, there are still some problems with the long‐term performance of Ti alloys, and therefore several surface modification methods are reviewed to further improve their biological activity, wear resistance, and corrosion resistance. Finally, the biocompatibility of Ti and its alloys is concluded. Summarizing the findings from literature, future prediction is also conducted.
This paper reviews the recent development in Ti alloys and their biomedical applications, including additive manufacturing, porous powder metallurgy, and severe plastic deformation applied in the manufacturing and the influenced microstructures and properties. Nevertheless, some problems exist in long‐term performance of Ti alloys. Hence, several surface modification methods are reviewed to improve their biological activity, wear resistance, and corrosion resistance.
Electron beam melting (EBM), as one of metal additive manufacturing technologies, is considered to be an innovative industrial production technology. Based on the layer‐wise manufacturing technique, ...as‐produced parts can be fabricated on a powder bed using the 3D computational design method. Because the melting process takes place in a vacuum environment, EBM technology can produce parts with higher densities compared to selective laser melting (SLM), particularly when titanium alloy is used. The ability to produce higher quality parts using EBM technology is making EBM more competitive. After briefly introducing the EBM process and the processing factors involved, this paper reviews recent progress in the processing, microstructure, and properties of titanium alloys and their composites manufactured by EBM. The paper describes significant positive progress in EBM of all types of titanium in terms of solid bulk and porous structures including Ti–6Al–4V and Ti–24Nb–4Zr–8Sn, with a focus on manufacturing using EBM and the resultant unique microstructure and service properties (mechanical properties, fatigue behaviors, and corrosion resistance properties) of EBM‐produced titanium alloys.
Electron beam melting (EBM), a metal additive manufacturing technology, has the ability to produce high quality metal parts. This paper reviews recent progress in all types of titanium alloys in terms of solid and porous structures, with a focus on the microstructure and service properties (mechanical properties, fatigue behaviors, and corrosion resistance properties) of EBM‐produced titanium alloys.
The class activation maps are generated from the final convolutional layer of CNN. They can highlight discriminative object regions for the class of interest. These discovered object regions have ...been widely used for weakly-supervised tasks. However, due to the small spatial resolution of the final convolutional layer, such class activation maps often locate coarse regions of the target objects, limiting the performance of weakly-supervised tasks that need pixel-accurate object locations. Thus, we aim to generate more fine-grained object localization information from the class activation maps to locate the target objects more accurately. In this paper, by rethinking the relationships between the feature maps and their corresponding gradients, we propose a simple yet effective method, called LayerCAM. It can produce reliable class activation maps for different layers of CNN. This property enables us to collect object localization information from coarse (rough spatial localization) to fine (precise fine-grained details) levels. We further integrate them into a high-quality class activation map, where the object-related pixels can be better highlighted. To evaluate the quality of the class activation maps produced by LayerCAM, we apply them to weakly-supervised object localization and semantic segmentation. Experiments demonstrate that the class activation maps generated by our method are more effective and reliable than those by the existing attention methods. The code will be made publicly available.
Thanks to a considerable number of fascinating properties, titanium (Ti) and Ti alloys play important roles in a variety of industrial sectors. However, Ti and Ti alloys could not satisfy all ...industrial requirements; the degradation of Ti and Ti alloys always commences on their surfaces in service, which declines the performances of Ti workpieces. Therefore, with aim to further improve their mechanical, corrosion and biological properties, surface modification is often required for Ti and Ti alloys. This article reviews the technologies and recent developments of surface‐modification methods with respect to Ti and Ti alloys, including mechanical, physical, chemical, and biochemical technologies. Conventional methods have limited improvement in the properties and/or restriction on the geometry of workpieces. Therefore, many advanced surface‐modification technologies have emerged in recent decades. New methods make Ti and Ti alloys have better performance and extended applications. With requirement of high surface properties in future. Understanding the mechanism in various surface‐modification methods, combining the advantages of current technologies and developing new coating materials with high performance are required urgently. As such, incorporation of different surface‐modification technologies with high‐performance modified layers may be the mainstream of surface modifications for Ti and Ti alloys.
The technologies and recent development of surface‐modification methods for titanium (Ti) and Ti alloys are reviewed. Such technologies have expanded the applications of Ti and Ti alloys in the past and present due to their enhanced surface properties. Likewise, the mainstream of surface modifications for Ti and Ti alloys in the future is also discussed.
We explore spatial symmetry breaking of a dipolar Bose-Einstein condensate in the thermodynamic limit and reveal a critical point in the phase diagram at which crystallization occurs via a ...second-order phase transition. This behavior is traced back to the significant effects of quantum fluctuations in dipolar condensates, which moreover stabilize a new supersolid phase, namely a regular honeycomb pattern with high modulational contrast and near-perfect superfluidity.
The SLM-produced Ti-6Al-4V alloy exhibits a higher corrosion rate in 1 M HCl solution than that in 3.5wt.% NaCl solution and XZ-plane of the SLM-produced Ti-6Al-4V alloy gives rise to the inferior ...corrosion resistance compared with its XY-plane.
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Corrosion resistance of selective laser melted Ti-6Al-4V was investigated.XY-plane of Selective laser melted alloy shows a better corrosion resistance.More α⿿ and less β-Ti weaken the corrosion resistance of XZ-plane.
Electrochemical measurements and microstructural analysis were performed to study the corrosion resistance of different planes of Ti-6Al-4V alloy manufactured by selective laser melting (SLM). The electrochemical results suggest that its XY-plane possesses a better corrosion resistance compared to XZ-plane in 1 M HCl solution, in spite of slight difference in 3.5wt.% NaCl solution, suggesting that the different planes exhibit more pronounced distinction in corrosion resistance in harsher solution system. The inferior corrosion resistance of XZ-plane is attributed to the presence of more α⿲ martensite and less β-Ti phase in microstructure for XZ-plane than for XY-plane of the SLM-produced Ti-6Al-4V alloy.
Metallic glasses (MGs) with the metastable nature and random atomic packing structure have attracted large attention in the catalytic family due to their superior catalytic performance. In contrast, ...their crystalline counterparts are restricted by the highly ordered packing structure, fewer surface active sites, and crystallographic defects for catalytic activity. The uncertainty of the different catalytic mechanisms and the intrinsic characteristics correlated to MGs and their crystalline counterparts become a major impediment to promote their catalytic efficiencies and widespread applications. Herein, it is reported that the excellent catalytic behavior in Fe‐based MGs goes through a detrimental effect with the partial crystallization, but receives a compelling rejuvenation in the full crystallization. Further investigation reveals that multiphase intermetallics with electric potential differences in fully crystallized alloys facilitate the formation of galvanic cells. More importantly, extensively reduced grain boundaries due to grain growth greatly weaken electron trapping and promote inner electron transportation. The relatively homogenous grain‐boundary corrosion in the intermetallics contributes to well‐separated phases after reaction, leading to refreshment of the surface active sites, thereby quickly activating hydrogen peroxide and rapidly degrading organic pollutants. The exploration of catalytic mechanisms in the crystalline counterparts of MGs provides significant insights into revolutionize novel catalysts.
Fully crystallized alloys gained by annealing of metallic glasses show excellent rejuvenated catalytic capabilities for ultrafast activation of peroxide. As galvanic cells form in the fully crystallized alloys, a grain growth contributing to extensively reduced grain boundaries greatly weakens electron trapping and promotes inner electron transportation, providing a significant insight into exploit novel catalysts.
There is a need to find better strategies to promote wound healing, especially of chronic wounds, which remain a challenge. We found that synovium mesenchymal stem cells (SMSCs) have the ability to ...strongly promote cell proliferation of fibroblasts; however, they are ineffective at promoting angiogenesis. Using gene overexpression technology, we overexpressed microRNA‐126‐3p (miR‐126‐3p) and transferred the angiogenic ability of endothelial progenitor cells to SMSCs, promoting angiogenesis. We tested a therapeutic strategy involving controlled‐release exosomes derived from miR‐126‐3p‐overexpressing SMSCs combined with chitosan. Our in vitro results showed that exosomes derived from miR‐126‐3p‐overexpressing SMSCs (SMSC‐126‐Exos) stimulated the proliferation of human dermal fibroblasts and human dermal microvascular endothelial cells (HMEC‐1) in a dose‐dependent manner. Furthermore, SMSC‐126‐Exos also promoted migration and tube formation of HMEC‐1. Testing this system in a diabetic rat model, we found that this approach resulted in accelerated re‐epithelialization, activated angiogenesis, and promotion of collagen maturity in vivo. These data provide the first evidence of the potential of SMSC‐126‐Exos in treating cutaneous wounds and indicate that modifying the cells—for example, by gene overexpression—and using the exosomes derived from these modified cells provides a potential drug delivery system and could have infinite possibilities for future therapy. Stem Cells Translational Medicine 2017;6:736–747
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