State Key Laboratory of Solidification Processing

Laboratory of, China

State Key Laboratory of Solidification Processing

Laboratory of, China
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Li N.,Shaanxi Key Laboratory Of Friction Welding Technologiesnorthwestern Polytechnical Universityxianpr China | Li W.Y.,State Key Laboratory of Solidification Processing | Yang X.W.,State Key Laboratory of Solidification Processing
Materials and Corrosion | Year: 2017

Aluminum alloy 2024-T3 sheets were friction stir welded (FSWed) and the microstructure in the thermo-mechanically affected zone (TMAZ) and stir zone (SZ) were characterized. The effect of corrosion exposure on the joints was evaluated under different solutions (3.5wt% NaCl, 3.5wt% NaCl+1wt% HCl, and exfoliation corrosion-EXCO) by immersion tests as well as electrochemical measurements; specimens with pre-corroded joints were subjected to tensile testing. The results indicate that TMAZ and SZ of the FSWed joints present different corrosion performances for the three corrosion solutions. SZ shows higher corrosion resistance than TMAZ, as the dissolution of precipitates in SZ considerably decreases its susceptibility to corrosion. The joint exposed to the EXCO solution has suffered higher mechanical properties degradation than the other two solutions, while the corrosion resistance of SZ and TMAZ was associated with the presence of the S-type precipitates and the concentration of H+ and Cl- ions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ma T.,State Key Laboratory of Solidification Processing | Li W.,State Key Laboratory of Solidification Processing
Advanced Engineering Materials | Year: 2016

Linear friction welding is employed to weld a Ti2AlNb-based alloy. The oxidation behavior of three different zones, i.e., base metal, weld zone, and thermo-mechanically affected zone is studied at 800°C exposed to air. The oxidation kinetics of the specimens consist of an initial parabolic kinetic and followed by a linear kinetic. For the base metal, absorption of more oxygen due to higher amount of α2 phase leads to the thickest oxidation scale, while the preferential formation of Al2O3 for the joint contributes to better oxidation resistance. The presence of AlNbO4 for all the three zones can be observed after a prolong exposure in air, leading to a drastic acceleration of oxidation rate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Zhan M.,State Key Laboratory of Solidification Processing | Du H.,State Key Laboratory of Solidification Processing | Liu J.,State Key Laboratory of Solidification Processing | Ren N.,State Key Laboratory of Solidification Processing | And 4 more authors.
Materials Science and Engineering A | Year: 2010

The plastic forming of welded tubes is becoming more widespread in the aircraft and automotive industries owing to the manufacturing advantages of low cost, short production period and great variety. To obtain a more precise constitutive model of a welded tube with a straight weld line, a method of establishing constitutive models of the weld bead and heat-affected zone (HAZ) metal based on a mixed material tensile experiment and microhardness test is proposed by introducing the influence of the HAZ metal and considering the variation in flow stress across the HAZ. In addition, it is proposed to use cross-sectional samples of the tube in measuring the tube microhardness so that the characteristics of the microhardness throughout the weld zone and HAZ can truly be represented. Constitutive models of a Q215 welded tube are established using the proposed method. The proposed method is assessed by comparing results with those obtained using the original method based on the rule of mixtures. The effects of the sample size on the constitutive model of a welded tube have been investigated by simple tensile testing simulation and experiment. The results show that tensile specimens of sufficient width to include the weld bead, HAZ, and parent metal are suitable considering the constraint among the weld bead, HAZ, and parent metal. © 2010 Elsevier B.V. All rights reserved.


Zhou Y.,Xian Jiaotong UniversityXian710049 China | Liu F.,State Key Laboratory of Solidification Processing | Wang H.,Electronic Materials Research Laboratory
Polymer Composites | Year: 2015

Significant progress has been made recently in developing the organic-inorganic composites with high thermal conductivity, low dielectric constant, and dielectric loss, for applications in the electronic packaging and substrates. Many studies have shown that some polymers filled with high thermal conductivity and low dielectric loss ceramics are suitable for electronic packaging for device encapsulation. Until now, extensive attentions have been paid to the preparation of polymeric composites with high thermal conductivity and low dielectric loss for the application in electronic packaging. In contrast, the thermal conductivities of these dielectric materials are still not high enough and that might restrict their serviceable range. Herein, we briefly reviewed recent progress in this field and introduced a kind of novel composites with surface insulation modified metal aluminum cores to form multilayer coating structures as fillers in polyimide matrix for electronic applications. This structure can significantly improve the thermal conductivity and dielectric properties of composites and give some insights into the effects of modified fillers of composite materials. Such multilayer core-shell structures should have great potentials for the improvement of nanoparticle-based fillers and applications of electronic packaging. © 2015 Society of Plastics Engineers.


Liu G.,China University of Technology | Liu L.,State Key Laboratory of Solidification Processing | Zhang G.J.,China University of Technology | Zhang J.,State Key Laboratory of Solidification Processing
Materials Science Forum | Year: 2015

A Re-containing single-crystal superalloy was processed with conventional radiation high rate solidification (HRS) and liquid-metal cooling (LMC) techniques, respectively. Compared with the HRS castings, LMC castings exhibited the greatly refined dendrite structures and lower segregation. At the withdrawal rate of 50 μm/s, the primary and secondary dendrite arm spacing of LMC casting was 103 and 19 μm, which were reduced by 60% and 53% compared to the counterpart of HRS castings. Moreover, higher withdrawal rates significantly shortened the characteristic diffusion distance and reduced the residual segregation of refractory elements after homogenization-solution treatments, which is beneficial for improving the local phase stability of Re-containing superalloys. © (2015) Trans Tech Publications, Switzerland.


Tong L.,State Key Laboratory of Solidification Processing | Chen Z.,State Key Laboratory of Solidification Processing | Zong H.,State Key Laboratory For Mechanical Behavior Of Materialsxian Jiaotong Universityxian710049Pr China | Huang L.,State Key Laboratory of Solidification Processing | And 2 more authors.
Physica Status Solidi (B) Basic Research | Year: 2016

Little is known about the band states of armchair AlN nanoribbons (aAlNNRs), so we investigated their band states of perfect and single C-chain-doped aAlNNRs by first-principles calculations. For aAlNNRs with a width N<12, the nonedge C-chain doping can lead to the distribution of the conduction-band minimum (CBM) electrons transferring from the central part of the ribbon to the C-N-Al ring. One representative model for aAlNNRs with a width of 8 ([aAlNNR]8) was mainly studied. In contrast to a h-AlN monolayer, we find a second degenerate state (above the Fermi level) in perfect [aAlNNR]8, which stems from the Al-s py and hybridized N-s pz orbitals. However, both degenerate states are suppressed by single C-chain doping. For N≥12, wherever a C-chain locates, the CBM always displays similarly delocalized characteristics. Our study can not only show that single C-chain doping can significantly modify the band states, but also can enrich the understanding of aAlNNRs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Jiang Y.,State Key Laboratory of Solidification Processing | Sun B.,State Key Laboratory of Solidification Processing | Liu F.,State Key Laboratory of Solidification Processing
Applied Mechanics and Materials | Year: 2012

A general analytical phase transformation model has been proposed and successfully applied to describe the crystallization of amorphous alloys. The "additivity rule" is proved to be compatible with the analytical model; the effects of anisotropic growth based on Monte Carlo (MC) simulations is reinterpreted using the analytical approach; and an improved temperature integral is also proved to be compatible with the analytical model. Kinetic analysis basing on the analytical model declares the transformation mechanism, e.g. nucleation, growth and impingement mode. On this basis, the kinetic behaviors of isothermal and non-isothermal crystallization of amorphous Zr 50Al 10Ni 40 are analyzed. © (2012) Trans Tech Publications, Switzerland.


Li Y.,Northwestern Polytechnical University | Xie F.,Northwestern Polytechnical University | Wu X.,Northwestern Polytechnical University | Li X.,Northwestern Polytechnical University | Li X.,State Key Laboratory of Solidification Processing
Applied Surface Science | Year: 2013

Si-Al-Y co-deposition coatings were prepared on a Ti-Al alloy by pack cementation process at 1050 for 4 h. The effects of pack Y2O 3content (from 0 to 5 wt%) on the microstructure and constituent phases of the co-deposition coatings were studied, the wear resistance of the substrate and the coated specimens were also compared at 600°C in air. The results showed that the pack Y2O3 content imposed strong influences on both coating structures and phase constituents. The coatings prepared with the pack mixtures con-taining 1 and 2 wt% Y2O 3were composed of an TiSi2out layer, an (Ti, X) 5Si4 and (Ti, X)5Si3(X represents Nb and Cr)middle layer, an TiAl2inner layer and an Al-rich interdiffusion zone. However, the constituent phases changed into TiSi 2,(Ti, X)5Si4and (Ti, X)5Si 3in the out layer of the coating prepared with the pack mixture containing 3 wt% Y2O3. Moreover, (Ti, X) 5Si4and (Ti, X)5Si3phases were observed in the outer layers of the coatings prepared with the pack mixtures containing 0 and 5 wt% Y2O3. The coating growth could be catalyzed obviously when the content of Y2O3in the pack mixtures increased from 1 to 2 wt%, but this phenomenon was not observed when further increased the pack Y2O3content to 3 or 5 wt%. Si-Al-Y co-deposition treatment improved the surface hardness and wears resistance of the Ti-Al alloy significantly. The wear resistance of the tested samples could be sorted in the following sequence: 1%Y2O 3-coating > no RE-coating > bare Ti-Al alloy. © 2013 Elsevier B.V. All rights reserved.


Li H.,State Key Laboratory of Solidification Processing | Li H.,Northwestern Polytechnical University | Li Y.,Northwestern Polytechnical University | Ke W.,Northwestern Polytechnical University | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2015

In-depth understanding and quantification of the forming characteristics of the taper-rolling process are crucial for process design and parameters determination in order for producing a desired precise helical blade from a metal strip. To this end, a quantitative study is carried out on this process through finite element (FE) simulation and experiment. For the FE simulation, a 3D model is established by handling problems observed in experiments about strip bite, sideways movement, and interference with the rolls and then is calibrated in numerically dynamic effect and validated by experiment. The results show that the plastic hoop and thickness strain components exhibit linearly increasing distributions from the inner to outer rim of the blade, which is a result of the hyperbolic-curve distributed roll gap. Thus, small radial strain that coordinates the deformation in hoop and thickness directions varies from positive to negative across the blade width. As a result, less spread and smaller bending radius have been achieved on the blade than that on the in-plane bent ring under the same conditions. Screw diameter increases with increasing initial position of the strip (H), initial roll gap (S1) and rolls offset (S2), and screw pitch increases with increasing S1 and S2 but is uncertain with increasing H, the rules of which are quantified. The reason is attributed to the change of roll gap and thus the change of strain distribution with varying H, S1, and S2. Then, three forming defects (turning-I, turning-II, and wrinkling) are defined and correspondingly the stable condition is determined as 0.9 <= az/b0 <= 1.6 and t1/t0 ≥ 0.3. Thus, a formable window of H, S1, and S2 for sound formation is determined, within which the forming limit defined as the achievable minimum relative bending radius Rin/b0 is quantified by simulation and validated by experiment. © 2015 Springer-Verlag London


Zhongwei C.,State Key Laboratory of Solidification Processing | Haifang Z.,State Key Laboratory of Solidification Processing | Ruijie Z.,Northwestern Polytechnical University
China Foundry | Year: 2010

Iron is the most deleterious impurity in the Al-Si-Mg casting alloys and can easily form inter-metallic compounds that can significantly affect the subsequent behavior of material properties. Using differential scanning calorimetry (DSC) and microstructural analysis, how the Be and Fe additions affect the iron-bearing phase in A357 alloys was investigated. The results show that the iron-bearing phase in A357 alloy comprises mainly the plate like β-AI 5FeSi and a small quantity of the script-type p{cyrillic}-AI 8FeMg 3Si 6; and that the plate-like β-AI 5FeSi proportion increases with increasing iron content in the alloy. The iron-bearing phase is mostly transformed from the plate-like β-AI 5FeSi to the script-type p{cyrillic}-AI 8FeMg 3Si 6 with the addition of Be in the alloy. The hardness of alloy samples was also tested. The results show that both the increasing iron content and Be content can increase the hardness of the alloy. This may be contributed to the change of morphology and distribution of the iron-bearing phase in A357 alloy with the addition of iron or Be to the alloy.

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