Co-reporter:Z.R. Wang, J.B. Qiang, Y.M. Wang, Q. Wang, D.D. Dong, C. Dong
Acta Materialia 2016 Volume 111() pp:366-376
Publication Date(Web):1 June 2016
DOI:10.1016/j.actamat.2016.03.072
Abstract
It is known that bulk metallic glasses are interpreted by simple composition formulas [cluster](glue atom)1 or 3, with the valence electron number per unit formula (e/u) being universally 24. In the present work, this cluster-plus-glue-atom approach was explored in great details for the objective of establishing the standard procedures towards designing bulk metallic glasses, via example of Ti-Cu-based alloys. The cluster selection from devitrification phases and the e/u calculation methods were first clarified. Then, step-by-step procedures toward developing alloys with high glass forming abilities were proposed. The cluster formula [Ti-Cu6Ti8]Cu3, with e/u ≈ 23.6, was taken as the basic composition formula. Upon properly alloying with Zr and Sn, large glass forming abilities up to 5 mm in diameter were experimentally reached at Ti40Zr10Cu56.94Sn3.06 via copper mold suction casting. Another alloy Ti45.71Zr11.43Cu39.29Sn3.57 showed a slightly inferior glass forming ability of 4 mm but contained the highest Ti(Zr) content of all the Ti-based BMGs, Ni-, Pd- and Be-free. The thus-obtained bulk metallic glasses generally exhibited high compressive strengths of about 1.8 GPa and nearly zero ductilities, except a Co-alloyed one, [Ti-Cu5.3Sn0.5Co0.2Ti6.2Zr1.8]Cu3, whose compressive ductility exceeded 6%.
Co-reporter:Zijian Wang, Dandan Dong, Shuang Zhang, Yanping Ma, Chuang Dong
Journal of Alloys and Compounds 2016 Volume 654() pp:340-343
Publication Date(Web):5 January 2016
DOI:10.1016/j.jallcom.2015.08.244
•A correlation between GFA and cluster formula issued from the cluster-plus-glue-atom model was revealed.•Three characteristics of binary BMG formulas were unveiled, which may guide new BMG design.•Binary eutectics in Cu-(Zr, Hf, Ti), Ni-(Nb, Ta), and Al–Ca systems were accurately interpreted.Compositions of typical bulk metallic glasses (BMGs) and boron-containing eutectics have been previously interpreted by cluster formulas issued from the cluster-plus-glue-atom model. In the present work, binary BMG composition formulas are established via dissociating dual-cluster formulas for their relevant eutectics. It is unveiled that BMG formulas satisfy three ubiquitous rules: cluster formula of the form [cluster](glue atom)1 or 3 with 24 valence electrons per unit formula, the center and the glue sites occupied by the same atomic species, and the BMG composition falling within the eutectic zone. These characteristics may serve as the finger prints for good glass formers and eventually the BMG design tool.
Co-reporter:Yongjun Chen, Jianbin Qiang, Chuang Dong
Intermetallics 2016 Volume 68() pp:23-30
Publication Date(Web):January 2016
DOI:10.1016/j.intermet.2015.09.001
•The quasicrystal abrasive exhibits prominent smear-type wear, but conventional ones remove and scratch easily soft metals.•The quasicrystal abrasive produces a flattened surface with the least surface removal when used to polish soft metals.•Cutting- and smearing-dominated wear is distinguished by the indent size shrinking with respect to surface removal depth.The abrasive polishing behavior of Al62Cu25.5Fe12.5 quasicrystal on Cu, Al and austenite stainless steel alloys were investigated, to compare with commonly used hard abrasives such as diamond, alumina and silica. The quasicrystal abrasive showed a dominating smearing-type wear mechanism, in sharp contrast to all the other three abrasives, as reflected by large indent size shrinking with respect to surface removal depth. The quasicrystal abrasive polishing, producing a flattened surface with minor depth removal, may open new application fields where low-wearing and fine surface finishing are demanded.
Co-reporter:Hailian Hong;Qing Wang
Science China Materials 2015 Volume 58( Issue 5) pp:355-362
Publication Date(Web):2015 May
DOI:10.1007/s40843-015-0049-y
It was recently known that the compositions of industrial alloy specifications generally satisfy simple composition formulas issued from short-range-order structural units in their basic solid solutions. In present work, Cu-Ni face-centered-cubic alloys were further addressed by introducing the cluster-plus-glue-atom model for the short-range-order structural descriptions. Composition formulas covering only the first twelve and the second six neighbor shells in the face-centered-cubic lattice are proposed, [Cu-Cu12](Cu,Ni)6 for the Cu-rich alloys and [Ni-Ni12]Cu6 ~ [Ni-Ni12](Cu5Ni) for Monel alloy, the only Ni-rich alloy specficiation, where the square-bracketed part represents a cuboctahedral cluster. The alloy specification selection is also discussed in terms of valence electron numbers per unit formula. The present work confirms that well-established industrial alloys have simple composition rules that reflect the intrinsic short-range-order local structures in the solid solutions.工业合金牌号成分一般满足简单的成分式, 我们认为该成分式源自其固溶体中的化学近程有序. 在本文中, 我们通过引入用于描述近程有序结构的团簇与连接原子模型, 进一步详细阐述面心立方结构Cu-Ni合金的工业牌号成分解析. 我们提出的团簇成分式只涉及第一近邻的十二配位立方八面体团簇(方括号部分)和第二近邻的八面体(连接原子部分), 理想满足元素间相互作用: 富铜端的白铜对应于[Cu-Cu12](Cu,Ni)6团簇式, 在富镍端只有蒙乃尔一种工业牌号合金, 用团簇式[Ni-Ni12]Cu6 ~ [Ni-Ni12](Cu5Ni)来解析. 我们还指出, 团簇式对应着特定的价电子总数规律. 本工作进一步证实, 工业合金牌号背后隐藏着体现固溶体近程有序本质的成分规律.
Co-reporter:Zhen Li, Ruiqian Zhang, Qianfeng Zha, Yingmin Wang, Jianbing Qiang, Chuang Dong
Progress in Natural Science: Materials International 2014 Volume 24(Issue 1) pp:35-41
Publication Date(Web):February 2014
DOI:10.1016/j.pnsc.2014.01.010
The composition characteristics of maraging stainless steels were studied in the present work investigation using a cluster-plus-glue-atom model. The least solubility limit of high-temperature austenite to form martensite in basic Fe–Ni–Cr corresponds to the cluster formula [NiFe12]Cr3, where NiFe12 is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula [NiFe12](Cr2Ni) with surplus Ni was then determined to ensure the second phase (Ni3M) precipitation, based on which new multi-component alloys [(Ni,Cu)16Fe192](Cr32(Ni,Mo,Ti,Nb,Al,V)16) were designed. These alloys were prepared by copper mould suction casting method, then solid-solution treated at 1273 K for 1 h followed by water-quenching, and finally aged at 783 K for 3 h. The experimental results showed that the multi-element alloying results in Ni3M precipitation on the martensite, which enhances the strengths of alloys sharply after ageing treatment. Among them, the aged [(Cu4Ni12)Fe192](Cr32(Ni8.5Mo2Ti2Nb0.5Al1V1)) alloy (Fe74.91Ni8.82Cr11.62Mo1.34Ti0.67Nb0.32Al0.19V0.36Cu1.78 wt%) has higher tensile strengths with YS=1456 MPa and UTS=1494 MPa. It also exhibits good corrosion-resistance in 3.5 wt% NaCl solution.
Co-reporter:Y. Samih, G. Marcos, N. Stein, N. Allain, E. Fleury, C. Dong, T. Grosdidier
Surface and Coatings Technology 2014 Volume 259(Part C) pp:737-745
Publication Date(Web):25 November 2014
DOI:10.1016/j.surfcoat.2014.09.065
•A martensitic steel was subjected to high current pulsed electron beam (HCPEB).•Fine δ-Fe grains formed via epitaxial growth from the substrate.•Larger γ–grains nucleated from surface of the melt and transformed into martenite.•Despite a complex multi-phase microstructure, the corrosion resistance was enhanced.•Increase in Cr content improved the corrosion and deep-hardening was not revealed.The surface of the AISI 420 martensitic stainless steel was subjected to High Current Pulsed Electron Beam (HCPEB) treatment. The microstructure in the melted layer consisted of a three phase mixture: (i) fine δ-Fe grains formed via epitaxial growth from the substrate, (ii) larger γ–grains nucleated from the top surface of the melt and (iii) some needles-like variants issued from the solid state martenitic transformation. Despite this complex multi-phase microstructure, the corrosion performance, tested in a sulfuric acid solution, was significantly enhanced by the HCPEB treatment. The increase in corrosion potential and delayed pitting are essentially attributed to an increase in Cr content, rising from 13.3 wt. % in the bulk to about 14 wt. % at the surface, together with a very limited amount of surface craters. This low density of craters did not give rise to significant deep hardening in the sub-surface but the top surface melted layer hardness was increased by more than 50% because of the triggering of the martensitic transformation.
Co-reporter:Shao-Xu Wang, Shi-Guang Quan, Chuang Dong
Thermochimica Acta 2012 Volume 532() pp:92-95
Publication Date(Web):20 March 2012
DOI:10.1016/j.tca.2010.12.005
The kinetics of the glass transition of Zr57.2Al21.4Ni21.4 bulk metallic glass (BMG) was studied using differential scanning calorimetry (DSC) with continuous heating of the sample at various heating rates. The heating rate dependence of the glass transition temperature (Tg) was investigated. By employing Moynihan and Kissinger models, the activation energy (E) of the glass transition was determined. It was shown that the transition process cannot be described in terms of single activation energy. The variation of E with the extent of conversion (α) was further analyzed by using two isoconversional methods (Kissinger–Akahira–Sunose method and Vyazovkin method). Evidence of the variation of E throughout the glass transition region was observed, which indicated that the transformation from amorphous to a supercooled liquid phase of Zr57.2Al21.4Ni21.4 BMG was a complex process.Research highlights▶ The glass transition process of Zr57.2Al21.4Ni21.4 bulk metallic glass (BMG) can not be described in terms of single activation energy. ▶ The activation energy throughout the glass transition region increases with increasing the extent of conversion. ▶ The transformation from amorphous to a supercooled liquid phase of Zr57.2Al21.4Ni21.4 alloy is a complex process.
Co-reporter:Baozeng Li, Junjie Gu, Qing Wang, Chunjun Ji, Yingmin Wang, Jianbing Qiang, Chuang Dong
Materials Characterization 2012 Volume 68() pp:94-101
Publication Date(Web):June 2012
DOI:10.1016/j.matchar.2012.04.002
The cluster-plus-glue-atom model is applied in the composition interpretation of Monel alloys. This model considers ideal atomic nearest neighbor configurations among the constituent elements and has been used in understanding compositions of complex alloys like quasicrystals, amorphous alloys, and cupronickels. According to this model, any structure can be expressed by cluster formula [cluster](glue atom)x, x denoting the number of glue atoms matching one cluster. According to this model, two groups of experimental composition series [Fe1Ni12]Cux and [FeyNi12]Cu5 were designed which fell close to conventional Fe-containing Monel alloys. The designed alloys after solution treatment plus water quenching, are monolithic FCC Ni-based solid solutions. Among them, the [Fe1Ni12]Cu5 alloy has the highest corrosion resistance in simulated sea water, and its performance is superior to that of industrial Monel 400 alloy.Highlights►A stable solid solution model is proposed using our “cluster-plus-glue-atom model”. ►This model is used to develop Monel corrosion resistant alloys. ►Single FCC structure is easily retained. ►The alloys show good corrosion properties. ►This work contributes to the general understanding of engineering alloys.
Co-reporter:Fa-quan Gong, jing Wen, Ya-jun Zhao, Jian-bing Qiang, Ying-min Wang, Xian-xiu Mei, Chuang Dong, Zhi-guang Wang
Journal of Nuclear Materials 2012 429(1–3) pp: 221-225
Publication Date(Web):
DOI:10.1016/j.jnucmat.2012.05.046
Co-reporter:Yuanjun Su, Jun Xu, Chuang Dong, Wenqi Lu
Surface and Coatings Technology 2012 206(14) pp: 3159-3164
Publication Date(Web):
DOI:10.1016/j.surfcoat.2011.10.042
Co-reporter:Baozeng Li, Qing Wang, Yingmin Wang, Jianbing Qiang, Xiaona Li, Chunjun Ji, Xiaolei Guo, Chuang Dong, Liqiang Zuo
Materials & Design 2012 40() pp: 171-175
Publication Date(Web):
DOI:10.1016/j.matdes.2012.04.006
Co-reporter:Guang Han, Jianbing Qiang, Fengwei Li, Liang Yuan, Shiguan Quan, Qing Wang, Yingmin Wang, Chuang Dong, Peter Häussler
Acta Materialia 2011 Volume 59(Issue 15) pp:5917-5923
Publication Date(Web):September 2011
DOI:10.1016/j.actamat.2011.05.065
Abstract
The electrons per atom ratio e/a is an important factor in discussing the stabilization mechanism of metallic glasses. However, the e/a assignment is complicated by hybridization effects, particular in transition metal systems. We have previously proposed the “cluster-plus-glue-atom” model for metallic glasses and the relevant cluster formula [cluster](glue atom)x, x ∼ 1 or 3. In the present paper, this model is combined with Häussler’s global-resonance model into a so-called cluster-resonance model. This model allows the calculation of the Fermi vector and hence the effective e/a of an ideal metallic glass. By assuming an ideal dense packing of the clusters, the atomic density can be obtained and e/a becomes associated with the number of atoms in the unit cluster formula Z. Experiments are carried out to verify these correlations. Alloys like Cu8Zr5Al, Ni4Zr9Al2 and [Ni7Nb5Zr]Ni3, possessing locally the highest glass-forming abilities, are interpreted by cluster formulae, with their Zs being determined by their e/a values. Such verifications not only validate the proposed e/a calculation schemes and the models behind them, but also support the ideal metallic glass feature of bulk metallic glasses with high glass-forming abilities.
Co-reporter:X.D. Zhang, S.Z. Hao, X.N. Li, C. Dong, T. Grosdidier
Applied Surface Science 2011 Volume 257(Issue 13) pp:5899-5902
Publication Date(Web):15 April 2011
DOI:10.1016/j.apsusc.2011.01.136
Abstract
The microstructure, hardness and corrosion resistance of commercially pure Ti treated by low energy high current pulsed electron beam (LEHCPEB) have been investigated. The thin near-surface melted layer rapidly solidified into β and subsequently transformed into ultrafine α′ martensite. This has led to a drastic improvement of the corrosion properties and a significant increase (more than 60%) in hardness of the top surface.
Co-reporter:Hua Chen;Jianbing Qiang;Qing Wang;Yingmin Wang
Israel Journal of Chemistry 2011 Volume 51( Issue 11-12) pp:1226-1234
Publication Date(Web):
DOI:10.1002/ijch.201100139
Abstract
Compositions of binary Al-TM (TM=Cr to Ni) quasicrystals are interpreted with a unified cluster formula [icosahedron](glue)1 using the newly developed cluster–resonance model and the e/a formalism. The icosahedra are chosen from the corresponding approximants by considering large radial atomic density, high degree of isolation, and narrow distribution of the shell atoms. Icosahedral quasicrystals are expressed by an icosahedron plus one averaged icosahedron atom as the glue atom [icosahedron](icosahedron/13)1, characterized by e/a ∼1.83–1.85, while decagonal quasicrystals are expressed by an icosahedron plus one TM atom, with e/a ∼1.71–1.78. The total electrons accommodated in unit cluster formulas of different Al-TM quasicrystals have the same value approaching 24, which implies that the cluster formulas are both chemical and electronic structural units.
Co-reporter:Liang Yuan, Chang Pang, Yingmin Wang, Qing Wang, Jianbing Qiang, Chuang Dong
Intermetallics 2010 Volume 18(Issue 10) pp:1800-1802
Publication Date(Web):October 2010
DOI:10.1016/j.intermet.2010.01.023
The Ni–Nb–Zr bulk metallic glass composition was analyzed by our cluster-plus-glue-atom model using a eutectic-related binary cluster M-Ni6Nb6, M = 0.5Ni + 0.5Nb, which was derived from a eutectic phase Ni7Nb6 (Fe7W6 type). A composition formula [M-Ni6Nb4MZr]Ni3 was then proposed, where the combination of one M and one Zr atom had an almost equal atomic size as a Nb atom to be substituted for. Alloy rods with 3 mm in diameter were obtained using copper mould suction casting. XRD results showed that compositions [M-Ni6Nb5-xMZrx]Ni3, x = 0.76, 0.84, 0.92, 1, 1.08, 1.16 formed single glassy phases, conforming to the proposed formula.
Co-reporter:C.L. Zhu, Q. Wang, Y.M. Wang, J.B. Qiang, C. Dong
Intermetallics 2010 Volume 18(Issue 5) pp:791-795
Publication Date(Web):May 2010
DOI:10.1016/j.intermet.2009.12.007
Co-reporter:Chun-lei Zhu;Qing Wang;Jie Zhang
International Journal of Minerals, Metallurgy, and Materials 2010 Volume 17( Issue 3) pp:323-326
Publication Date(Web):2010 June
DOI:10.1007/s12613-010-0312-x
Bulk metallic glass (BMG) formation was explored in the Fe-B-Si-Nb alloy system though combined use of the atomic cluster line approach and the minor alloying strategy. The basic ternary compositions in the Fe-B-Si system were determined by the intersection points of two cluster lines, namely, Fe-B cluster to Si and Fe-Si cluster to B. 3at%–4at% Nb was added to the quaternary Fe-B-Si-Nb alloy. The casting experiments revealed that good glass-forming ability (GFA) occurred at the (Fe73.4Si8.2B18.4)96Nb4 composition, and 3-mm diameter BMG samples were made. The glass transition temperature (Tg), crystallization temperature (Tx), and supercooled liquid region (ΔTx=Tx−Tg) of this BMG were measured to be 866, 889, and 23 K, respectively. The BMG shows a high Vickers hardness of about Hv 1164, a Young’s modulus of 180 GPa, and a good corrosion resistance in the solutions of 1 mol/L HCl and 3wt% NaCl.
Co-reporter:Chuang Dong, Weirong Chen, Yingmin Wang, Jianbing Qiang, Qing Wang, Yi Lei, Monique Calvo-Dahlborg, Jean-Marie Dubois
Journal of Non-Crystalline Solids 2007 Volume 353(32–40) pp:3405-3411
Publication Date(Web):15 October 2007
DOI:10.1016/j.jnoncrysol.2007.05.162
It has been widely accepted that quasicrystals and at least some metallic glasses are built up with icosahedral clusters. Information about the cluster structures can be obtained from crystalline counterparts. In this paper, we will describe the formation rules of bulk metallic glasses, originally developed for quasicrystals, by combining cluster structures with phase diagram features. We will introduce the e/a-constant and e/a-variant criteria for ternary systems, and e/a-constant and atomic size constant criteria for quaternary systems. We will show how the glass forming composition optimization is realized by applying these rules in the Zr–Al–Ni and Zr–Al–Ni–Cu systems. In both systems the optimized glass-forming composition is related to a common binary icosahedral cluster Zr9Ni4 derived from the fcc Zr2Ni phase. A novel route to reach amorphous forming composition is also attempted by mixing Al-based quasicrystal-forming compositions with Zr.
Co-reporter:Qing Wang, Jianbing Qiang, Yingmin Wang, Junhai Xia, Chuang Dong
Journal of Non-Crystalline Solids 2007 Volume 353(32–40) pp:3425-3428
Publication Date(Web):15 October 2007
DOI:10.1016/j.jnoncrysol.2007.05.093
The formation of bulk metallic glasses (BMG) in the Cu-rich Cu–Zr–Ti ternary system is studied by using the ‘e/a-variant line criterion’. Three such lines, (Cu9Zr4)1−xTix, (Cu61.8Zr38.2)1−xTix and (Cu56Zr44)1−xTix, are defined in the Cu–Zr–Ti system by linking three binary compositions Cu9Zr4, Cu61.8Zr38.2 and Cu56Zr44 to the third element Ti. The binary compositions Cu9Zr4, Cu61.8Zr38.2 and Cu56Zr44 correspond to specific Cu–Zr binary clusters. BMGs are obtained by copper mould suction casting method with Ti contents of 7.5–15 at.%, 7.5–12.5 at.% and 5–12 at.%, respectively along the (Cu9Zr4)1−x Tix, (Cu61.8Zr38.2)1−xTix and (Cu56Zr44)1−xTix lines. The BMGs on each composition line manifest decreased thermal stabilities and glass forming abilities (GFAs) with increasing Ti contents. The maximum GFA appears at Cu64Zr28.5Ti7.5, with characteristic thermal parameters of Tg = 736 K, Tx = 769 K, Tg/Tl = 0.627 and γ = 0.403, which are all superior to those reported for the known Cu60Zr30Ti10 BMG.
Co-reporter:J. Wu, Q. Wang, F. Chen, Y.M. Wang, J.B. Qiang, C. Dong
Intermetallics 2007 Volume 15(5–6) pp:652-654
Publication Date(Web):May–June 2007
DOI:10.1016/j.intermet.2006.10.007
The present paper is concerned with the formation of the ternary Sm-based Sm–Al–Ni bulk metallic glasses. Composition design is carried out using our e/a- and cluster-related criteria. Three bulk metallic glasses, Sm54Al23Ni23, Sm56Al22Ni22 and Sm58Al21Ni21, are obtained by suction casting into rods with diameter of 3 mm. All of them share a constant e/a = 1.5 and fall along the e/a-constant composition line in the ternary composition diagram. The Sm54Al23Ni23 BMG exhibits the best thermal stability and glass-forming ability, which is located at the intersecting point of the e/a-constant line and the Sm7Ni3–Al cluster line.
Co-reporter:Q. Wang, J.B. Qiang, J.H. Xia, J. Wu, Y.M. Wang, C. Dong
Intermetallics 2007 Volume 15(5–6) pp:711-715
Publication Date(Web):May–June 2007
DOI:10.1016/j.intermet.2006.10.025
The present paper investigates the bulk metallic glass formation in Cu–Zr–Al and Cu–Zr–Ti ternary systems by using the cluster line criterion. The binary basic clusters are first selected for constructing cluster lines. Three cluster selection rules are proposed: topologically dense packing, chemical short-range order and composition distance to deep eutectics. Three Cu–Zr clusters Cu8Zr5, Cu6Zr5 and Cu5Zr6 are selected according to the three rules. The bulk metallic glass-forming ranges in these two systems are determined. The thermal characteristic parameters of the Cu–Zr–Al BMGs on every composition line increase with increasing Al content and decrease with increasing Ti content in the Cu–Zr–Ti glass-forming range. The optimum bulk amorphous compositions in the Cu–Zr–Al system are Cu58.1Zr35.9Al6 and Cu39.7Zr47.1Al13.2, respectively, located in Cu8Zr5–Al and Cu5Zr6–Al cluster lines. In the Cu–Zr–Ti system, the Cu64Zr28.5Ti7.5 composition with the largest Tg/Tl is located in Cu9Zr4–Ti cluster line and the Cu57.6Zr32.4Ti10 composition with the largest glass-forming ability is located in Cu64Zr36–Ti line.
Co-reporter:Jianxin Zou, Thierry Grosdidier, Kemin Zhang, Chuang Dong
Acta Materialia 2006 Volume 54(Issue 20) pp:5409-5419
Publication Date(Web):December 2006
DOI:10.1016/j.actamat.2006.05.053
Abstract
This work investigates the mechanism of surface modification associated with the high-current pulsed electron beam (HCPEB) treatment of a D2 steel with increasing numbers of pulses. The surface layers were melted and resolidified but the treated surfaces showed very different features. This variation is essentially due to the different levels of homogeneity and carbide dissolution. It is demonstrated that the presence of carbides served as nucleation sites for the surface eruption phenomenon that creates craters on the surface. After a sufficient number of pulses, most of the carbides in the surface layer were dissolved and an almost crater-free homogeneous melted layer consisting of a very stable nano-austenite structure was formed. The HCPEB technique is thus demonstrated to be a versatile technique for surface microstructure modification involving, in the case of steels, austenite stabilization and ultrafine grain formation.
Co-reporter:Zhang Zhiguo, Liu Tianwei, Xu Jun, Deng Xinlu, Dong Chuang
Surface and Coatings Technology 2006 Volume 200(16–17) pp:4918-4922
Publication Date(Web):27 April 2006
DOI:10.1016/j.surfcoat.2005.04.060
Zirconium nitride thin films were synthesized by a microwave electron cyclotron resonance (MW-ECR) plasma enhanced unbalanced magnetron sputtering (PE-UMS) technique. The results of plasma diagnostics by an electrostatic probe indicate that the electron temperature decreases with increasing nitrogen flow rate. The substrate ion current initially increases as the nitrogen flow rate increases at a low flow and then decreases with increasing nitrogen flow. The nitrogen concentration in the films increases and the grain size decreases while the N2+ ion density increases. The metastable Zr3N4 phase occurs as the N/Zr atomic ratio reaches 1.4. The films become amorphous as the N/Zr atomic ratio is higher. The corresponding microhardness of the deposited films increases from 22.5 GPa to the maximum of 26.8 GPa, and then decreases linearly to 19.8 GPa as the N2 flow rate increases from 8 to 14 sccm. The mechanism of the influence of the plasma characteristics on the microstructure and mechanical properties of the deposited films were discussed.
Co-reporter:Lin Guoqiang, Bai Xiao, Dong Chuang, Wen Lishi
Surface and Coatings Technology 2005 Volume 194(2–3) pp:325-329
Publication Date(Web):1 May 2005
DOI:10.1016/j.surfcoat.2004.07.074
The main factors influencing substrate temperature such as ion bombardment, heat radiation, and heat conductivity are analyzed for Pulsed-Bias Arc Ion Plating (PBAIP). The wave profile of the pulsed bias voltage, varying from −1000 to 0 V, is basically rectangle. This characteristic periodic energy input has an average energy density being equal to the product of that of the DC Arc Ion Plating (DCAIP) and the duty cycle in PBAIP. A temperature model based on energy conservation for the substrate temperature is thus established, which incorporates input ion power, heat radiation and heat conductivity. Experiments are also conducted to verify the calculation.
Co-reporter:Yingmin Wang, Xinfang Zhang, Jianbing Qiang, Qing Wang, Dehe Wang, Dejun Li, Chan Hung Shek, Chuang Dong
Scripta Materialia 2004 Volume 50(Issue 6) pp:829-833
Publication Date(Web):March 2004
DOI:10.1016/j.scriptamat.2003.12.014
Composition optimization for locating the composition with the largest glass forming ability in the Al–Co–Zr system is attempted in this investigation. The criteria that we have developed are respectively related to a specific conduction electron concentration, termed the e/a-constant criterion, and to a specific cluster structure, termed the e/a-variant criterion. For this system, the two criteria are incarnated into the composition line with constant e/a=1.5 and the Co4Zr9–Al composition line. Bulk metallic glasses are obtained by suction casting for compositions with e/a=1.3–1.5, with their thermal stabilities and glass forming abilities being increased with increasing e/a ratios. The crossing point of the e/a=1.5 line and the Co4Zr9–Al line gives the composition Al23.5Co23.5Zr53 with the largest GFA (e.g. Tg/Tm=0.637), superior to the reported Al20Co25Zr55 alloy with Tg/Tm=0.621.
Co-reporter:Chuang Dong, Xiaona Li, Dong Nie, Lei Xu, Ze Zhang
Thin Solid Films 2004 Volume 461(Issue 1) pp:48-56
Publication Date(Web):2 August 2004
DOI:10.1016/j.tsf.2004.02.060
Carbon-doped β-FeSi2 films synthesized by ion implantation is investigated with the aim to fabricate high-quality semiconducting β-FeSi2 layer on silicon substrate. According to our TEM cross-section observations, the carbon-doped films are of better quality than the non-doped ones for their improved uniform film thickness, smooth β/Si interface and high thermal stability. In particular, annealing at 500–700 °C leads to the formation of a flat and continuous β-type silicide layer. Optical absorption measurements show that the carbon doping does not influence the band structure. We further point out that the presence of multiple and incoherent orientation relationships between β and Si, discussed within the framework of the near coincident site lattice theory, is a key factor responsible for the difficulty in obtaining high-quality epitaxial β films.
Co-reporter:Q. Wang, Y.M. Wang, J.B. Qiang, X.F. Zhang, C.H. Shek, C. Dong
Intermetallics 2004 Volume 12(10–11) pp:1229-1232
Publication Date(Web):October–November 2004
DOI:10.1016/j.intermet.2004.07.002
The present paper is concerned with the formation of the Cu-based Cu–Zr–Al bulk metallic glasses (BMGs). Composition optimization for BMG formation was realized by using an ‘e/a-variant criterion’ that had been successfully applied in the Zr–Al–Ni and Zr–Al–Co systems. This criterion was incorporated into the ternary phase diagram by constructing a composition line (Cu61.8Zr38.2)1−xAlx, which was defined by linking the optimum binary composition (Cu61.8Zr38.2, a deep eutectic in this case) and the third element. BMGs were obtained within an e/a span from 1.24 to 1.3 along this composition line. Thermal analysis results indicate that these BMGs manifest increased thermal stability and glass forming ability (GFA) with increasing e/a ratios. The maximum appears in Cu58.1Zr35.9Al6 with the e/a value of 1.3 which is the highest among our samples. The characteristic thermal parameters of this BMG are Tg=760 K, Tg/Tl=0.648, which are all superior to those reported for the known Cu55Zr40Al5 BMG.
Co-reporter:Jianxin Zou, Aimin Wu, Chuang Dong, Shenzhi Hao, Zhenmin Liu, Haitao Ma
Surface and Coatings Technology 2004 Volume 183(2–3) pp:261-267
Publication Date(Web):24 May 2004
DOI:10.1016/j.surfcoat.2003.08.087
A duplex surface treatment scheme, combining arc deposition with high-current pulsed electron beam (HCPEB) post treatment, has been applied to rapid surface alloying of AISI H13 steel in order to improve high-temperature oxidation resistance. An Al coating as thick as 10 μm was deposited on AISI H13 by arc deposition. The coating was then post-treated with HCPEB. Due to rapid surface heating and melting, part of the Al precoating was dissolved into the substrate surface, forming a saturated surface alloy layer. High temperature oxidation resistance is improved by approximately 40 times as compared to the untreated sample.
Co-reporter:Ying Qin, Jianxin Zou, Chuang Dong, Xiaogang Wang, Aimin Wu, Yue Liu, Shengzhi Hao, Qingfeng Guan
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 2004 Volume 225(Issue 4) pp:544-554
Publication Date(Web):October 2004
DOI:10.1016/j.nimb.2004.06.008
Physical models and numerical simulations are applied to describe the thermal–dynamical processes of the high current pulsed electron beam (HCPEB) treatment. The simulation of the temperature distributions reveals an ultrahigh heating/cooling rate in the order of 108–109 K/s, as well as rapid melting and re-solidification within microseconds in time and micrometers in depth. It is also pointed out that the melting starts at a sublayer about 1–2 μm in depth, which constitutes the crater formation mechanism. A temperature-induced dynamic thermal stress fields can then generate three principal stress, the quasi-static stress, the thermoelastic stress and the shock stress, the latter two being stress waves. The thermoelastic stress wave has small amplitudes less than 0.1 MPa. The shock stress wave however is a typical nonlinear wave, several hundreds of MPa in amplitudes, much stronger than the thermoelastic stress wave, and has a strong impact on materials structure and properties far beyond the heat-affected zone. The maximum compressive quasi-static stress in the surface layer reaches several hundreds of MPa, which easily induces surface deformation in metallic materials.
Co-reporter:W. Chen, Y. Wang, J. Qiang, C. Dong
Acta Materialia 2003 Volume 51(Issue 7) pp:1899-1907
Publication Date(Web):18 April 2003
DOI:10.1016/S1359-6454(02)00596-7
Abstract
Electron concentration and atomic size rules are important criteria for bulk metallic glass formation. According to these rules, a series of new Zr-Al-Ni-Cu amorphous alloys with a constant e/a ratio of 1.4 and an average atomic size of 0.1496 nm was designed. All the alloys have high glass forming abilities, large supercooled liquid regions ΔTx, and large reduced glass transition temperatures Trg. The best glass forming composition is located near Zr63.8Al11.4Ni17.2Cu7.6. Its glass forming ability is higher than that of the Inoue alloy Zr65Al7.5Ni10Cu17.5.
Co-reporter:Y.M Wang, C.H Shek, J.B Qiang, C.H Wong, W.R Chen, C Dong
Scripta Materialia 2003 Volume 48(Issue 11) pp:1525-1529
Publication Date(Web):June 2003
DOI:10.1016/S1359-6462(03)00129-5
In the present paper (Zr76Ni24)1−xAlx alloys were prepared to investigate the influence of e/a, electron number per atom, on their glass-forming abilities. The bulk metallic glasses (BMGs) obtained in this alloy series have an e/a span from 1.37 to 1.53. Their thermal stability increases with the e/a ratios. The largest thermal stability is found at Zr60Al21Ni19 with the highest possible e/a=1.53. These BMGs manifest negative temperature coefficients of resistivity and a nearly linear T-dependence of resistivity within the temperature span 80–293 K. The validity of the Nagel–Tauc conjecture, 2kf≈kp for the stabilities of these BMGs is discussed. The e/a-based rule is a promising way to locate glass-forming compositions in the Zr-based multi-component alloy systems.
Co-reporter:C Dong, A Wu, S Hao, J Zou, Z Liu, P Zhong, A Zhang, T Xu, J Chen, J Xu, Q Liu, Z Zhou
Surface and Coatings Technology 2003 Volumes 163–164() pp:620-624
Publication Date(Web):30 January 2003
DOI:10.1016/S0257-8972(02)00657-6
Electron beams are becoming an increased subject of interest for materials processing. While continuous electron beams have already found wide applications in drilling, hardening, cutting and welding, the advantage of a pulsed electron beam has just emerged. It generates a high power density up to 108–109 W/cm2 at the target surface. Such a high energy is deposited only in a very thin layer within a short time, and causes superfast processes such as heating, melting and evaporation. A dynamic stress field induced in these processes leads to significant modification effects in the material. The combination of these processes provides the material with improved physicochemical and mechanical properties unattainable with ordinary surface treatment techniques. The present paper reports our recent research work on surface treatment by high-current pulsed electron beam (HCPEB). HCPEB is produced on system ‘Nadezhda-2’ with an energy range of 20–40 kV. A series of pure Al and mold steels were studied. Some of them were pre-coated with C, Cr, Ti or TiN powders. A strong enhanced diffusion effect was revealed: the surface elements diffuse approximately several micrometers in depth into the substrate only after several bombardments. Tribological behaviors of these samples were characterized and significant improvement in wear resistance was found. Finally, TEM analysis reveals the presence of stress waves generated by the coupling of thermal and stress fields, which constitutes the main cause of the enhanced diffusion.
Co-reporter:Chuang Dong, Li-Ming Zhang, Esther Belin-Ferré, Pierre Brunet, Jean-Marie Dubois
Materials Science and Engineering: A 2001 Volumes 304–306() pp:172-177
Publication Date(Web):31 May 2001
DOI:10.1016/S0921-5093(00)01455-6
Quasicrystals and their approximants are Hume-Rothery compounds having similar valence electron concentrations. According to this new understanding of approximants, some B2 superstructures can be regarded as a special group of approximants. The present paper examines surface characteristics of this group of approximants synthesized by hot pressing. Friction coefficient, surface energy and hardness are analyzed and influences from factors such as valence electron concentration and Al3p partial density of states at the Fermi energy are discussed. Specifically, we show that samples containing the B2 structure and its superstructures exhibit a friction coefficient which decreases with increasing e/a and reaches minimum at 1.86, the value of the quasicrystal. Therefore, the B2-based approximants and quasicrystals belong to one group of phases whose surface properties are mainly determined by electronic structure characteristics rather than crystal structures.
Co-reporter:Chuang Dong, Qiu-hua Zhang, De-he Wang, Ying-min Wang
Micron 2000 Volume 31(Issue 5) pp:507-514
Publication Date(Web):October 2000
DOI:10.1016/S0968-4328(99)00131-6
The Al3Cu4 alloy, with an e/a ratio of 1.86 being close to ternary Al–Cu–TM (transition metal) quasicrystals, has been chosen for the search of Al–Cu approximants. Phase structures and compositions were studied using TEM, X-ray diffraction and EPMA techniques. Two new phases were found: face-centered orthorhombic oF-Al43.2Cu56.8 (a=0.8166, b=1.4149, and body-centered orthorhombic oI-Al41.3Cu58.7 (oI, a=0.4083, b=0.7074, Their e/a ratios are the same as that of the Al–Cu–Fe icosahedral quasicrystal. Both are B2 superstructures and their unit cell components can be expressed approximately as oF-Al36Cu48□12 and oI-Al8Cu12□4 (□: vacancies). They both exist in twinning variants of the types 120°/[001] and 180°/[310]. Such twinning modes indicate that these orthorhombic phases are the decomposition products of a high-temperature parent phase ϵ2-Al2Cu3, the atomic structure of which shows pentagonal atomic arrangements. Further analysis on the twinning modes of oF and oI leads to the recognition of the chemical-twinning mode of the basic B2 structure as 180°/〈111〉B2. This kind of chemical twinning mode is responsible for the pentagonal atomic configuration in the Al–Cu approximants as well as for the pseudo-5-fold B2 twinning.
Co-reporter:C.H. Shek, Y.M. Wang, C. Dong
Materials Science and Engineering: A 2000 Volume 291(1–2) pp:78-85
Publication Date(Web):31 October 2000
DOI:10.1016/S0921-5093(00)00979-5
The microstructure of an as-cast Zr65Al7.5Ni10Cu17.5 ingot was studied by TEM and XRD analysis. Apart from the amorphous phase, five crystalline phases were identified, namely, face-centered cubic cF (0.5273 nm), body-centered tetragonal tI-Zr67.0Al1.7Ni8.4Cu22.9 (0.3216, 1.1120 nm), hexagonal hP1-Zr65.4Al11.7Ni11.6Cu11.3 phase (0.8175, 0.3337 nm), hexagonal phase hP2 (0.8175, 0.3337 nm), and orthorhombic oP (0.8210, 1.3187, 0.3315 nm). The latter two phases are superstructures of hP1. Compared with the nominal sample composition, the tI phase is rich in Cu but poor in Al, the hP1, hP2 and oP phases are to the contrary. All the phases, including the amorphous phase, are Hume–Rothery phases having nearly the same valence electron concentration. Therefore the amorphous phase is strongly related with its related crystalline phases in electronic structure. This should constitute an empirical criterion for high glass forming ability, i.e. the compositions of the amorphous alloy and its crystalline counterparts should be near a constant valence electron concentration ‘surface’ in the quaternary Zr–Al–Ni–Cu phase diagram.
Co-reporter:Shuang Zhang, Dandan Dong, Zijian Wang, Chuang Dong, Peter Häussler
Intermetallics (June 2017) Volume 85() pp:
Publication Date(Web):June 2017
DOI:10.1016/j.intermet.2017.02.019
•Composition formulas of Ni-(Nb, Ta) bulk metallic glasses are re-examined following refined composition design procedures.•The devitrification phases in Ni-(Nb, Ta) systems are NbNi3 (instead of Nb7Ni6 as assumed previously) and NiTa.•The principal clusters in these two systems are [Ni-Nb4Ni8] and [(Ni, Ta)-Ni6Ta6].•The best glass forming composition Ni62Nb38 is explained by [Ni-Nb4Ni8]Nb2Ni satisfying the 24-electron rule.•The bulk metallic glasses within 59–62 at.% Ni in Ni-Ta system are explained by the formula [(Ni, Ta)-Ni6Ta6]Ni3.It is known that bulk metallic glass compositions can be well interpreted by cluster formulas for stable liquids [cluster](glue atom)1 or 3, where the clusters are derived from relevant devitrification phases. In the present work, the glass forming composition formulas in Ni-Nb and Ni-Ta systems are fully examined. The procedures include choosing the appropriate eutectic crystalline phases, selecting the principal clusters via the criteria such as spherical periodicity and cluster isolation degree, and determining the glue atoms. After strictly following these procedures, the best glass forming compositions Ni62Nb38 in Ni-Nb system and the range 59–62 at.% Ni in Ni-Ta system are explained by formulas [Ni-Nb4Ni8]Nb2Ni and [M-Ni6Ta6]Ni3 (M is a random mixture of Ni and Ta) respectively.
Co-reporter:Dandan Dong, Chuang Dong
Journal of Non-Crystalline Solids (15 March 2017) Volume 460() pp:125-129
Publication Date(Web):15 March 2017
DOI:10.1016/j.jnoncrysol.2017.01.035
