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Zhou S.,Hefei University of Technology | Zhang Z.,Hefei University of Technology | Zhang Z.,National Metal and Materials Technology Center | Li M.,Hefei University of Technology | And 9 more authors.
Materials Characterization | Year: 2016

Primary particles formed in as-cast Al-5Mg-0.6Sc alloy and their role in microstructure and mechanical properties of the alloy were investigated using optical microscopy (OM), scanning electron microscopy (SEM), electron back-scatter diffraction (EBSD) and tensile testing. It was found that primary particles due to a close orientation to matrix could serve as the potent heterogeneous nucleation sites for α-Al during solidification and thus impose a remarkable grain refinement effect. Eutectic structure consisted of layer by layer of 'Al3Sc + α-Al + Al3Sc + ⋯' and cellular-dendritic substructure were simultaneously observed at the particles inside, indicating that these particles could be identified as the eutectics rather than individual Al3Sc phase. A calculating method, based on EBSD results, was introduced for the spatial distribution of these particles in matrix. The results showed that these eutectic particles randomly distributed in matrix. In addition, the formation of primary eutectic particles significant improved the strength of the Al-Mg alloy in as-cast condition, which is ascribed to the structural evolution from coarse dendrites to prefect fine equiaxed grains. On the other hand, these large-sized particles due to the tendency to act as the microcrack sources could cause a harmful effect in the ductility of Al-Mg-Sc alloy. © 2016 Elsevier Inc. All rights reserved.


Ding X.-Y.,Hefei University of Technology | Luo L.-M.,Hefei University of Technology | Luo L.-M.,Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province | Huang L.-M.,Hefei University of Technology | And 7 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2014

W-TiC composite powders were prepared by wet-chemical process, and ultra-fine grained W-TiC composites were fabricated by spark plasma sintering (SPS). The surface morphologies of W-TiC composite powders and the microstructure of W-TiC composites were studied. The results show that TiC powders are subjected to chemical activation pretreatment to obtain uniform distribution of defects on the surface of TiC powder, thus increasing the hydrophilicity of the TiC surface. The second phase TiC particles are homogeneously and dispersively distribute in the grains and grain boundaries by chemical reduction. The grain size, relative density and the Vicker hardness HV0.2 of the ultra-fine grained W-TiC composites by SPS are 400 nm, 95% and 1280, respectively. ©, 2014, Science Press. All right reserved.


Luo L.-M.,Hefei University of Technology | Luo L.-M.,Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province | Lu Z.-L.,Hefei University of Technology | Huang X.-M.,Hefei University of Technology | And 8 more authors.
Surface and Coatings Technology | Year: 2014

This paper proposes a new available palladium-free surface activation process on polycarbonate (PC) engineering plastic before electroless plating. Surface morphologies of the original plastic, activated plastic, surface and cross-sections after electroless plating were analyzed by field emission scanning electron microscopy (FE-SEM), energy dispersion spectrometry (EDS) and X-ray diffraction (XRD). The growth mechanism of copper layers was discussed. Results show that numerous folds, uneven steps, and other defects appear on the microscopic surface of activated plastic. After direct electroless plating, the plating layer on the plastic surface exhibits a closely bound granular distribution. Compared with the conventional pretreatment process, the plating layer possesses a similar morphology. The growth mechanisms are analyzed as follows: the reactant (Cu2+) in the electroless plating solution disperses and is adsorbed by the plastic surface in the process of Cu plating. The Cu particles that settled form the nucleus and grow. The growth process involves repeated gathering of nano-level Cu grains to form physically agglomerated Cu granules. The Cu grains finally merge to allow closely bound and evenly distributed copper plating. © 2014 Elsevier B.V.


Luo L.-M.,Hefei University of Technology | Luo L.-M.,Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province | Tan X.-Y.,Hefei University of Technology | Luo G.-N.,CAS Hefei Institutes of Physical Science | And 5 more authors.
Hejubian Yu Dengliziti Wuli/Nuclear Fusion and Plasma Physics | Year: 2014

This paper reviews the current method of solving the W/Cu interface connection and relieving the thermal stress by added adaptation layer. After analyzing the different adaptation layer, the best W/Cu adaptation layer is selected, and then the W/Cu layer structure optimization analysis is conducted. The results show that using W/Cu functionally graded materials as the combination of the adaptation layer has enough strength, and good thermal conductivity are more effective to alleviate thermal stress. In addition, this paper expounds the current method which utilizes the successfully prepared W/Cu functionally gradient materials as W/Cu adaptation layer used in the first wall materials. Finally, this paper has made the summary and prospect about that the functionally gradient materials of W/Cu used as the adaptation layer to solve the first wall material W/Cu interface connection. ©, 2014, Yuan Zi Neng Chuban She. All right reserved.


Ding X.-Y.,Hefei University of Technology | Luo L.-M.,Hefei University of Technology | Luo L.-M.,Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province | Tan X.-Y.,Hefei University of Technology | And 9 more authors.
Fusion Engineering and Design | Year: 2014

W-1 wt% Sm2O3 powders doped with highly uniform Sm2O3 were successfully synthesized by a novel wet chemical method followed by hydrogen reduction. The powders were consolidated by spark plasma sintering (SPS) at 1800 °C to suppress grain growth during sintering. The FE-SEM and HRTEM analysis, tensile test and thermal conductivity measurements were used to characterize these samples. The grain size, relative density of the bulk samples fabricated by SPS sintering were 4 μm and 97.8%, respectively. The tensile strength values of Sm2O3/W samples were higher than those of pure W samples. As the temperature rises from 25 to 800 °C, the thermal conductivity of pure W and W-1 wt% Sm 2O3 composites decreased with the same trend and the thermal conductivity of both samples was above 160 W/m K at room temperature. © 2014 Elsevier B.V.


Zhang J.,Hefei University of Technology | Zhu X.-Y.,Hefei University of Technology | Luo L.-M.,Hefei University of Technology | Luo L.-M.,Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province | And 5 more authors.
Hejubian Yu Dengliziti Wuli/Nuclear Fusion and Plasma Physics | Year: 2014

Addition of rare earth oxide to the tungsten can significantly refine the grain and improve high temperature stability of the tungsten alloys, which also have the dispersion strengthening effect and significant effect in the suppression of grain growth, controlling the re-crystallization grain shape and improving the mechanical properties of the materials. This paper expounds current situation of several techniques of preparing ODS-W from the perspective of preparation method of ODS-W particles and forecasts its development trend. ©, 2014, Yuan Zi Neng Chuban She. All right reserved.


Ding X.,Hefei University of Technology | Luo L.,Hefei University of Technology | Luo L.,Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province | Huang L.,Hefei University of Technology | And 7 more authors.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2015

Tungsten (W) powder was subjected to chemical activation pretreatment by immersion into an aqueous solution of hydrofluoric acid and ammonium fluoride, and then was reinforced with an ultrasonic wave at room temperature to obtain uniform distribution of defects (adsorbate island or steps, etc.) on the surface of W and TiC powder, increasing the surface activity of powder. W-1.5 wt% TiC composites were prepared by a powder metallurgy method. A field emission electron microscope was employed to observe the surface topography of the original and chemically pretreated powder and fracture morphologies of W-1.5 wt% TiC composites, and the sintering mechanism was discussed. The results show that under the condition of the same sintering process, the W-1.5 wt% TiC composites after activation treatment of sintered powder achieve a relative density 7% higher than that of the original powder and more compact organization. ©, 2015, Rare Metals Materials and Engineering Press. All right reserved.


Lu Z.-L.,Hefei University of Technology | Luo L.-M.,Hefei University of Technology | Luo L.-M.,Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province | Huang X.-M.,Hefei University of Technology | And 7 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2014

After the laser irradiation pretreatment and the ultrasonic assisted chemical plating, copper electroless plating was successfully prepared on Al2O3 ceramic substrate. The surfaces of the Al2O3 ceramic substrate before and after laser irradiation pretreatment and the electroless plating with the cross and scratches were analyzed by field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDS). The comparison experiments with traditional pretreatment process were also discussed. Result shows: combinations of a large number of microvoid and nano granular heaves appear on the surfaces of the Al2O3 ceramic substrate. Foreign particles are easily absorbed on this morphology of surface defects to complete the electroless plating. The plating and the substrate are combined well. Compared with the traditional process, the proposed one can avoid complicated procedures and the pollution from the noble metal 'Pd'. Moreover, the combination of the copper grains in the layer formed by the proposed process is considered to be better.


Lu Z.-L.,Hefei University of Technology | Wang Z.-C.,Hefei University of Technology | Luo L.-M.,Hefei University of Technology | Luo L.-M.,Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province | And 8 more authors.
Surface Engineering | Year: 2015

Electroless copper plating on Al2O3 substrate assisted by a new non-noble pretreatment is developed, the surface exhibits granular distribution, and the particles are closely bound except for the presence of defects (large holes). Heat treatment is performed at various temperatures to modify this surface. Results show that slight surface changes occur when the heat treatment temperature is below the recrystallisation temperature. Beyond the recrystallisation temperature, particles are fused, thereby modifying certain properties. However, heat stress also increases with increased temperature to 800°C, leading to poor bonding between the plating and substrate. When the temperature approaches the melting point of copper, plating exhibits an entirely different surface morphology. The molten copper in the cooling process forms shrinkages and dimples that reduce coating performance. The optimal heat treatment temperature is deemed to be approximately 500°C. © 2015 Institute of Materials, Minerals and Mining.


Ding X.-Y.,Hefei University of Technology | Luo L.-M.,Hefei University of Technology | Luo L.-M.,Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province | Chen H.-Y.,Hefei University of Technology | And 9 more authors.
Fusion Engineering and Design | Year: 2015

TiC/W ultra-fine powders were produced by one-step activation and chemical reduction process. The powders were consolidated by spark plasma sintering (SPS) at 1800 °C to suppress grain growth during sintering. The grain size, relative density and the Vicker hardness HV0.2 of the bulk sample fabricated by SPS were 3 μm, 98.6% and 471, respectively. The reduced Young's elastic modulus of the sintered W-1 wt.% TiC composites was 382.7 GPa. As the temperature rises from room temperature (RT) to 1100 K, the thermal conductivity of pure W and W-1 wt.% TiC composites decreased with the same trend. However, the thermal conductivity of the samples was both above 120 W/m K at RT. © 2015 Elsevier B.V. All rights reserved.

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