稀有金属(英文版) 2018,37(10),859-867

Dry ball milling and wet ball milling for fabricating copper-yttria composites

Fei Huang Hang Wang Jin-Shui Chen Bin Yang

School of Materials Science and Engineering, Jiangxi University of Science and Technology

Editorial Office, Nonferrous Metals of Science and Engineering Jiangxi University of Science and Technology

Institute of Engineering Research, Jiangxi University of Science and Technology

School of Materials Science and Engineering,Jiangxi University of Science and Technology

作者简介：*Bin Yang e-mail: yangbin65@126.com;

收稿日期：4 April 2017/

基金：financially supported by the National Key Research and Development Program of China (No. 2016YFB0301400);the Organization Department of Jiangxi Province(No. 2012215);the Education Department of Jiangxi Province (No. KJLD13041);the Outstanding Doctoral Dissertation Project Fund of JXUST (No. YB2017011);

Dry ball milling and wet ball milling for fabricating copper-yttria composites

Fei Huang Hang Wang Jin-Shui Chen Bin Yang

School of Materials Science and Engineering, Jiangxi University of Science and Technology

Editorial Office, Nonferrous Metals of Science and Engineering Jiangxi University of Science and Technology

Institute of Engineering Research, Jiangxi University of Science and Technology

School of Materials Science and Engineering,Jiangxi University of Science and Technology

Abstract：

Yttria-reinforced copper matrix composites were prepared by dry ball milling (DBM) and wet ball milling(WBM), respectively, followed by spark plasma sintering(SPS). It is to determine which milling process is better for fabricating Cu-Y₂O₃ composites. It is found that Cu-Y₂O₃composites synthesized by DBM exhibit better densification, mechanical and electrical properties than those by WBM. Less agglomeration of reinforcements in the bulk composites by DBM is responsible for the better performances. To further understand the reason of less agglomeration of Y2O₃ in the bulks by DBM, morphologies of prepared powders were investigated and analyzed. Higher ball's impact energy and the formation of copper oxide on the matrix surface during DBM process contribute to small matrix particles, which is beneficial for less agglomeration.

Keyword：

Cu-Y₂O₃ composites; Dry ball milling; Wet ball milling; Spark plasma sintering; Morphology;

Received： 4 April 2017/

1 Introduction

Particulate-reinforced copper matrix composites(PRCMCs) are a kind of artificial synthetic materials.Excellent electrical and thermal conductivities of copper and high strength,high modulus of the particle reinforcements are adopted for great performance of the composites.The most common particle reinforcements include oxides(e.g.,Al₂O₃),carbides (e.g.,SiC,TiC),nitrides (e.g.,AlN,Si₃N₄),borides (e.g.,TiB₂,ZrB₂).Oxides of trivalent rare earth oxides (RE₂O₃) exhibit excellent thermodynamic stability,but most of them are less used as inclusions in matrix for their fancy price [ 1] .Nevertheless,yttria,as one of the lowest cost rare earth oxides,not only have an excellent thermodynamic stability but also can form an interface of crystallographic orientation relationship with copper to further improve the strengthening effect of reinforcements on matrix in appreciate conditions [ 2] .These advantages of yttria draw more attentions on producing Cu-Y₂O₃ composites via various processing techniques,e.g.,in situ chemical reduction [ 3] ,friction stir processing [ 4] ,in situ reaction at the liquidus temperature [ 5] ,powder metallurgy [ 6] .

One of the most widely used methods in preparing PRCMCs is solid-state processing which involves many steps prior to final consolidation [ 7] .Powder processing is a crucial step for solid-state processing,which normally includes in situ chemical reduction method or ball milling method.The ball milling method enjoys greater popularity in the industry as it is much easier to be controlled.

Ball milling methods are usually pided into dry ball milling (DBM) and wet ball milling (WBM).DBM is mainly carried out in the environment of gas atmosphere,e.g.,argon ambient.WBM is mainly conducted in liquid environment,e.g.,ethanol.Both of the ball milling methods are used in fabricated metal matrix composites [ 3, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18] .Owing to different contents of reinforcements and different processing parameters in the references mentioned above,it is still not easy to judge whether DBM or WBM is better for synthesis of PRCMCs.Therefore,in the present work,the two milling methods followed by spark plasma sintering (SPS) for CuY₂O₃ composites are to be compared in terms of micros true ture,densification,mechanical properties and electrical conductivity.

2 Experimental

High-purity electrolytic copper powders and yttria powders were used as raw materials to fabricate CMCs.Average particle sizes of Cu and Y₂O₃ are 43 and 4μm,respectively.Contents of Y₂O₃ are 2 vol%,5 vol%,8 vol%and12 vol%.Powders are milled in horizontal ball mill (Xianyang Jinhong General Machinery Ltd.,GMJ/B) for 24 h.WBM was carried out in ethanol for it is easy to remove after milling.DBM was done in sealed nitrogen atmosphere,and nitrogen with the least protective effect was to represent commonly used atmosphere (H₂,Ar and N₂) [ 14] .The mill vessel was made of polyurethane (0.5 l),and the milling balls were made of zirconia (1,3 and 5 mm in diameter).The weight ratios of ball-to-powder and 3 kinds of milling balls are 5:1 and 1:1:1,respectively.The rotation speed of the mill vessel is 140 r·min^-1.Reduction was carried out in hydrogen atmosphere for DBM powders at500℃for 60 min before sintering.The powders after WBM were preserved in a vacuum drying oven at 80℃for 120 min.

The milled composites powders were sintered in a SPS device (Sumitomo Electric,SPS-1050).The sintering temperature was up to 920℃for 25 min,holding for5 min at the maximum temperature,followed by cooling in the furnace to room temperature.The entire heating was done under a vacuum below 10 Pa with a uniaxial pressure of 45 MPa.The geometry of the samples was a pellet of30 mm in diameter and 5 mm in height.Pure Cu powders were also processed according to the same procedure for the purpose of comparison.

Phases of bulk samples were analyzed by X-ray diffractometer (XRD,Bruker's,D8-Advance).The distribution of yttria in bulk composites and morphology of milled powders were observed and analyzed by scanning electron microscope (SEM,TESCAN,MIRA3 LMH).Laser particle size analyzer (LPSA,Sympatec GmbH,Helos/Rodos) was utilized to measure the distribution of particle size of milled CuY₂O₃ composite powders by different milling methods.Details of milled particle micro structure and contents were also studied by transmission electron microscopy (TEM,FEI,Tecnai G2-20).

Density of the consolidated Cu-Y₂O₃ composites was determined by Archimedes drainage method.Electrical conductivity of each sample was tested 5 times by SIG-MASCOPE SMP10 eddy current electro-conductive device at room temperature.Average values were adopted in the analysis.The tensile test was carried out by low load small sample drawing machine (Shimadzu,EZ graph) with a strain rate of 1×10^-3 s^-1.Dimensions of tensile specimens for tensile tests are shown in Fig.1 according to Ref. [ 19] .Specimens were then mechanically polished to a mirror finish.Microhardness test was performed at six different positions by digital display Vickers hardness tester (Shanghai optical Instrument factory,HXD-1000TMC/LCD) with a load of 0.98 N and loading time of10 s.

3 Results

3.1 Phase identification

XRD patterns of consolidated Cu-12 vol%Y₂O₃ microcomposites by different ball milling ways are illustrated in Fig.2.XRD patterns of the two samples both show the presence of pure copper and yttria only.No evidence of formation of any copper oxides in the composites is observed.Also,there is no signal for copper oxides in XRD patterns of 2 vol%,5 vol%,8 vol%Y₂O₃ samples,which are been shown here.

3.2 Distribution of Y2O3 particles

Back-scattered electron (BSE) images of Cu-Y₂O₃ composites by DBM and WBM are shown in Fig.3a-d,e-h,respectively.The bright regions in BSE images represent copper matrix,while the dark regions correspond to Y₂O₃particles.Morphology of Y₂O₃ particles in copper matrix is almost sphere-shape at low contents in Fig.3a,e.When the content of yttria increases,the shape of Y₂O₃ particles becomes more needle-like (Cu-12 vol%Y₂O₃ sample in Fig.3d,h).Taking WBM samples of CuY₂O₃ for example,agglomeration can be easy found with 5 vol%yttria,shown in Fig.3f,and the agglomeration size in this sample is approximately 10μm.More severe agglomeration is observed in the rest two samples with 8 vol%and 12 vol%Y₂O₃,as shown in Fig.3g,h.However,the Y₂O₃ particles exhibit slight agglomeration when DBM is introduced(Fig.3b,c).

Fig.1 Dimensions of specimen used for tensile tests (unit:mm)

Fig.2 XRD patterns of Cu-12 vol%Y₂O₃ composites by different ball milling ways

3.3 Densification

Figure 4a demonstrates density of Cu-Y₂O₃ composites against yttria content using DBM and WBM processes.The line with square stands for theoretical density,and those with circle and triangular symbols represent sintered density by DBM and WBM,respectively.With the increase in the content of Y₂O₃,both theoretical density and sintered density decrease.With the same Y₂O₃ content,the density of SPS sintered samples by DBM is obviously higher than that by WBM and closer to the theoretical density.Figure 4b shows densifications of SPS sintered samples.The densifications of DBM samples are about 98.5%,while those of WBM samples vary from 94%to 96%.This is due to less agglomeration of yttria particles in the bulk composites.It should also be noted that the densification values are higher than those prepared by traditional powder metallurgy technology (up to 94%) [ 6] .

3.4 Mechanical properties

True stress-strain curves of the CuY₂O₃ composites fabricated by different milling processes are shown in Fig.5.It is seen that the plastic property of the composites,no matter by DBM or WBM,decreases dramatically with the content of yttria increasing.In case of DBM,the yield strength of 8 vol%yttria-reinforced CMCs reaches the maximum value of about 239.8 MPa,and its elongation is7.34%.In case of WBM,the yield strength reaches the maximum of 138.2 MPa with yttria content of 12 vol%,and its elongation is only 2.78%.The results indicate that the elongation,yield strength and ultimate tensile strength of sintered samples by DBM are higher than those by WBM with the same content of yttria.

Fig.3 BSE images for distribution of Y₂O₃ in copper matrix by different ball milling processes:a DBM 2 vol%,b DBM 5 vol%,c DBM8 vol%,d DM 12 vol%,e WBM 2 vol%,f WBM 5 vol%,g WBM 8 vol%and h WBM 12 vol%

Fig.4 a Density and b densification of Cu-Y₂O₃ composites by different ball milling processes

Fig.5 True stress-strain curves of Cu-Y₂O₃ composites by a DBM and b WBM processes

The Vickers hardness with different contents of yttria is shown in Fig.6.The hardness values of DBM and WBM samples are on the rise with the content of yttria increasing.Note that the Vickers hardness of bulk samples by DBM can achieves the maximum of HV 112.8,increasing by73.5%compared with that of pure copper (HV 65.0).While the maximum Vickers hardness of WBM samples is HV91.3,increasing only 40.5%compared with that of pure copper.The results of microhardness of sintered samples are consistent with the stress-strain results.

Fig.6 Microhardness of Cu-Y₂O₃ composites by different ball milling processes

3.5 Electrical conductivity

Electrical conductivities of the Cu-Y₂O₃ composites produced by different ball milling methods are depicted in Fig.7.It illustrates that the conductivities of both DBM and WBM samples decrease along with the increase in the content of Y₂O_3.The conductivity of Cu-2 vol%Y₂O₃sample by DBM is 93.3 IACS%,while that by WBM is87.2 IACS%.When the content reaches 12 vol%,both conductivity of samples by DBM and WBM drops below80 IACS%.

Fig.7 Electrical conductivity of Cu-Y₂O₃ composites by different ball milling processes

4 Discussion

Properties of the sintered samples by two different ball milling processes are summarized in Table 1,e.g.,densification,yield strength,hardness and electrical conductivity.The properties of consolidated samples by DBM are generally superior to those by WBM.Also,the performance of the Cu-8 vol%Y₂O₃ sample by DBM is the best one—densification,Vickers hardness,yield strength and electrical conductivity of 99.07%,HV 112.8,239.8 MPa,and 83.0 I ACS%,respectively.This is obviously due to the distribution of Y₂O₃ in the matrix.However,it remains unclear why DBM leads to better distribution of yttria.

On the one hand,collision energy produced by falling impact of ball is one of the important parameters for ball milling.Therefore,during WBM,the impact force of the ball on powders is weakening due to the resistance of liquid to falling ball.The lower impact force of the ball influences particle size of both reinforcements and matrix.On the other hand,contamination of oxygen is unavoidable in the nitrogen atmosphere during DBM,so the copper powder surface tends to form small amount of oxides.These oxides are brittle and easy to crush to fine powders under the continuous impacts of the ball.Fine powders make less room for yttria to be aggregated.However,in the process of WBM,the copper powders are protected from oxygen in ethanol environment to form any oxide.Therefore,no brittle oxides effect can be expected in WBM case.The above explanation has been validated from two aspects:micro structure of copper powders after DBM and WBM and determination of oxygen content on the surface of copper powders.

SEM images for Cu-8 vol%Y₂O₃ composites powders of DBM and WBM before sintering are shown in Figs.8and 9,respectively.Figure 10 illustrates particle size distributions of the powder samples referring to Figs.8 and 9.In case of DBM,the particle size range (d₁₀-d₉₀) is between 4.19 and 30.50μm and the arithmetic mean size is13.94μm.Please note that d_x is the cumulative particle size for x%of particles.The morphology of copper shows flat flake shape with 1-2μm in thickness.The surface of the flake is relatively smooth,and some Y₂O₃ particles (about1μm) are embedded on it.In the case of WBM,the morphology of copper is still flat flake shape,but it is much thicker and coarser than that of DBM.Meanwhile,there are some Y₂O₃ particles (around 2μm) embedded on the surface.The particle size range (d₁₀-d₉₀) is from 5.19 to43.41μm,and the arithmetic mean size equals 18.94μm.The greater the particle is,the larger space exists between these particles.The larger space between copper powders will become flat during sintering.Therefore,the morphology of yttria clusters in bulk composite becomes“needlelike”shape.

If brittle oxides are formed on the copper surface,it is easier to obtain small copper particles.Therefore,there will be more oxygen on small particles surface than big ones.TEM was used to find the small copper particle by DBM and WBM.Figures 11 and 12 show the typical morphology of the small copper particles and energy-dispersive spectroscope (EDS) results using DBM and WBM,respectively.The oxygen contents on the surface are about1.4 wt%and 0.1 wt%,respectively.The results convince that more brittle oxides have been found on the copper particle surface by DBM—beneficial for particle fragmentation.

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Table 1 Characterization of Cu-Y₂O₃ by different ball milling processes and SPS

Fig.8 SEM images of 8 vol%Cu-Y₂O₃ powders after 24-h DBM with different magnifications

Fig.9 SEM images of 8 vol%Cu-Y₂O₃ powders after 24-h WBM with different magnifications

Fig.10 Histograms of particle size distribution of 8 vol%Cu-Y₂O₃ powders with a DBM and b WBM processes

Fig.11 a TEM image of copper particle and b EDS results using DBM showing oxygen contents of 1.5 wt%

Fig.12 a TEM image of copper particle and b EDS results using WBM showing oxygen contents of 0.1 wt%

As long as a layer of brittle oxide surrounded copper powders improves fragmentation,it can be speculated that DBM is better for ductile matrix powders,while WBM is better for brittle matrix powders.Table 2 demonstrates usage profiles of different properties of the matrix and reinforcements by DBM or WBM.There are in total 36papers under consideration.When the raw material or the matrix is brittle particles,the number of literatures using WBM is 13 [ 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32] which outpaces 8 more than that using DBM [ 33, 34, 35, 36, 37] .This could be reflecting that the brittle particles may become finer particles by WBM or achieve better properties.This is consistent with the studies comparing WBM and DBM for brittle quartz particles [ 38] and Al₂O₃-MoSi₂ composites [ 39] .

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Table 2 Different properties of materials by different ball milling processes

In the case of copper powders,almost all the studies [ 40, 41, 42, 43, 44, 45] (5 in 6) are using DBM,and the effects of various parameters of ball milling processes on morphology and properties of the powders have been studied.For examples,Menapace et al. [ 44] compared the copper particle size fabricated by copper powders with different initial oxygen contents by DBM.High initial oxygen content powders changed to much finer copper powder particles after 100-h DBM.However,the mechanical properties of SPS samples without hydrogen reduction were worse than those of lowoxygen content samples for oxides,slowing down the sinterability of the powder.Boytsov et al. [ 41] studied the evolution of copper powder microstructure with rotating disk speed,vial rotation speed and milling time in the air and obtained nanocrystalline copper powders.In the preparation of Y₂O₃,Al₂O₃,graphite,SiC and other reinforcements strengthened CMCs,most of references,more than three quarters of the references,employ ball milling in inert atmosphere [ 11, 12, 13, 14, 15, 16, 17, 18] ,while less than a third of the references [ 3, 8, 9, 10] adopt WBM in methanol or ethanol.From the relation of utilization number for WBM with brittle particles,it can be inferred that utilization number of DBM on ductile copper powder may,from another perspective,reflects the conclusion that CMCs obtained by DBM can achieve more uniform dispersion and better mechanical properties than those by WBM.

5 Conclusion

Two series Cu-Y₂O₃ composites powders with different contents of reinforcements were prepared by DBM and WBM,respectively.Microstructure,mechanical properties and electrical conductivity of these two series SPS sintered samples were analyzed.The mechanical properties and electrical conductivities of sintered samples fabricated by DBM with hydrogen reduction are better than those prepared by WBM.The performance of Cu-8 vol%Y₂O₃composites prepared by DBM is the best one among all the samples.The densification,Vickers hardness,tensile strength and electrical conductivity are 99.07%,HV 112.8,239.8 MPa and 83 IACS%,respectively.Less agglomeration of reinforcements in consolidated composites by DBM is attributed to the stronger ball's impact force and formation of copper oxide on the matrix surface during milling process.When the matrix is ductile material,finer particles and better properties of sintered materials can be obtained by DBM.However,if the matrix is brittle,it is better to use WBM.

Acknowledgements This study was financially supported by the National Key Research and Development Program of China (No.2016YFB0301400),the Organization Department of Jiangxi Province(No.2012215),the Education Department of Jiangxi Province (No.KJLD13041) and the Outstanding Doctoral Dissertation Project Fund of JXUST (No.YB2017011).One of the authors Fei Huang would like to thank Prof.Hao Chen and Dr.Xue-Hui Zhang for their advice.

参考文献

[1] Liu G. Rare Earth Materials. Beijing:Chemical Industry Press;2011. 44.

[2] Zhuo HO, Tang JC, Ye N. Strengthening mechanisms of Y_2O_3dispersion strengthened copper-based composites. Rare Metal Mat Eng. 2015;44(5):1134.

[3] Joshi PB, Bharati R, Palak N, Swati P, Khanna PK. Studies on copper-yttria nanocomposites:high-energy ball milling versus chemical reduction method. J Nanosci Nanotechnol. 2012;12(3):2591.

[4] Avettand-Fenoel MN, Simar A, Shabadi R, Taillard R, de Meester B. Characterization of oxide dispersion strengthened copper based materials developed by friction stir processing.Mater Design. 2014;60:343.

[5] Zhuo HO. Study of properties of nano-yttria dispersion strengthened copper-based composites prepared by in-situ reaction at liquidus temperature. Nanchang:University of Nanchang; 2015. 19.

[6] Zhen M, Geng HR, Li MM, Nie GL, Leng J. Effects of Y_2O_3 on the property of copper based contact materials. Compos B Eng.2013;52:51.

[7] Ibrahim IA, Mohamed FA, Lavernia EJ. Particulate reinforced metal matrix composites:a review. J Mater Sci. 1991;26(5):1137.

[8] Stobrawa JP, Rdzawski ZM, Gluchowski WJ. Dispersion and precipitation strengthened nanocrystalline and ultrafine grained copper. J Nanosci Nanotechnol. 2012;12(12):9102.

[9] Zhang XH, Lin CG, Cui S. Microstructure and properties of Al_2O_3 dispersion-strengthened copper fabricated by reactive synthesis process. Rare Met. 2014;33(2):191.

[10] Feng D, Chen YX, Fu LW, Li J, He JQ. SnSe+Ag2Se composite engineering with ball milling for enhanced thermoelectric performance. Rare Met. 2018;37(4):333.

[11] Akbarpour MR, Salahi E, Alikhani FH, Simchi A, Kim HS.Fabrication, characterization and mechanical properties of hybrid composites of copper using the nanoparticulates of SiC and carbon nanotubes. Materi Sci Eng A. 2013;572:83.

[12] Bozic D, Stasic J, Dimcic B, Vilotijevic M, Rajkovic V. Multiple strengthening mechanisms in nanoparticle-reinforced copper matrix composites. Bull Mater Sci. 2011;34(2):217.

[13] Carro G, Munoz A, Monge MA, Savoini B, Pareja R, Ballesteros C. Fabrication and characterization of Y_2O_3 dispersion strengthened copper alloys. J Nucl Mater. 2014;455(1-3):655.

[14] Liu WY, Zhang JB, Wu SJ, Hu MJ, Chen TT, Guo LL. Effects of Si on friction properties of Ti3SiC2/Al composites. Nonferrous Met Sci Eng. 2017;8(5):89.

[15] Dash K, Ray BC, Chaira D. Synthesis and characterization of copper-alumina metal matrix composite by conventional and spark plasma sintering. J Alloys Compd. 2012;516:78.

[16] Martin U, Kudashov DV, Heilmaier M, Oettel H. Microstructure and deformation behaviour of ultra-fine-grained ODS copper prepared by mechanical alloying. WIT Trans Built Environ.2004;6(7):341.

[17] Naser J, Riehemann W, Ferkel H. Dispersion hardening of metals by nanoscaled ceramic powders. Mater Sci Eng A. 1997;234-236:467.

[18] Wang X, Liang S, Yang P, Fan Z. Effect of milling time on electrical breakdown behavior of Al_2O_3/Cu composite. J Mater Eng Perform. 2010;19(6):906.

[19] Chandrasekhar SB, Wasekar NP, Ramakrishna M, Babu PS, Rao TN, Kashyap BP. Dynamic strain ageing in fine grained Cu-lwt%Al_2O_3 composite processed by two step ball milling and spark plasma sintering. J Alloys Compd. 2016;656:423.

[20] Masaki H, Wada S. Wear of media balls during the ball milling of Si3N4 powder. Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi. 1993;101(2):221.

[21] Meng H, Zhang Z, Zhao F, Qiu T. Preparation of WC nanoparticles by twice ball milling. Int J Refract Met Hard Mater. 2013;41:191.

[22] Nagai Y, Lai GC. Preparation of fine AIN powders by wet ball-milling and their characterization. Nippon Seramikkusu Kyokai. 1997;105(1):6.

[23] Jeong YK, Nakahira A, Peter MED, Niihara K. Effect of milling conditions on the strength of alumina-silicon carbide nanocomposites. J Am Ceram Soc. 1997;80(5):1307.

[24] Anandajothi M, Ramanathan S, Ananthi VP. Narayanasamy 1.Fabrication and characterization of Ti6A14 V/TiB2-TiC composites by powder metallurgy method. Rare Met. 2017;36(10):806.

[25] Zhang YF, Wang LJ, Jiang W, Chen LD. Effect of different milling methods on the fabrication of Al_2O_3-TiC nanocomposites by SPS. J Inorg Mater. 2005;20(6):167.

[26] Luo H, Luan DC, Wang ZY, Wang L. Influence of high power ball mill technology on sturcture of tungsten-copper composites.Powder Metall Ind. 2007;17(1):30.

[27] Maneshian MH, Simchi A. Solid state and liquid phase sintering of mechanically activated W-20wt.%Cu powder mixture. J Alloys Compd. 2008;463:153.

[28] Ozkal B, Upadhyaya A, Ovecoglu ML, German RM. Comparative properties of 85W-15Cu powders prepared using mixing,milling and coating techniques. Powder Metall. 2010;53(3):236.

[29] Su W, Sun Y, Feng J, Liu J, Ruan J. Influences of the preparation methods of WC-Co powders on the sintering and microstructure of coarse grained WC-8Co hardmetals. Int J Refract Met Hard Mater. 2015;48:3 69.

[30] Zhang FL, Wang CY, Zhu M. Nanostructured WC/Co composite powder prepared by high energy ball milling. Scr Mater.2003;49(11):1123.

[31] Zhang Q, Shi X, Yang H, Duan X. Microstructure and properties of W-15Cu alloys prepared by mechanical alloying and spark plasma sintering process. J Wuhan Univ Technol Mater Sci Ed.2008;23(3):399.

[32] Zhang YL, Cui X, Zhu M, Wang CY. Nanostructured WC-Co composite powder fabricated by high-energy ball milling and spark plasma sintering. Cem Carbride. 2007;24(2):80.

[33] Shon IJ, Kwon H, Oh HS. Effect of milling on properties and consolidation of AIN by high-frequency induction heated sintering. Electron Mater Lett. 2014;10(2):337.

[34] Zhang Y, Wang L, Jiang W, Chen L, Bai G. Microstructure and properties of Al_2O_3-TiC nanocomposites fabricated by spark plasma sintering from high-energy ball milled reactants. J Eur Ceram Soc. 2006;26(15):3393.

[35] Hewitt SA, Kibble KA. Effects of ball milling time on the synthesis and consolidation of nanostructured WC-Co composites. Int J Refract Met Hard Mater. 2009;27(6):937.

[36] Mao CH, Du J. Study on nano-structured WC-Co composite powders made by mechanical milling. Rare Met. 1998;17(4):2.

[37] Wang FT, Wu YC, Wang TG, Ren R. Characteristics of W-20Cu nano-crystallite composites fabricated by mechanical alloying. J Nanosci Nanotechnol. 2010;10(8):5422.

[38] Huang Z, Zhou W, Tang X, Zhu J. Effects of milling methods on the dielectric and the mechanical properties of hot-pressed sintered MoSi2/Al_2O_3 composites. J Alloys Compd. 2011;509(5):1920.

[39] Kotake N, Kuboki M, Kiya S, Kanda Y. Influence of dry and wet grinding conditions on fineness and shape of particle size distribution of product in a ball mill. Adv Powder Technol. 2011;22(1):86.

[40] Wu SP, Gao RY, Xu LH. Preparation of micron-sized flake copper powder for base-metal-electrode multi-layer ceramic capacitor. J Mater Process Technol. 2009;209(3):1129.

[41] Boytsov O, Ustinov AI, Gaffet E, Bernard F. Correlation between milling parameters and microstructure characteristics of nanocrystalline copper powder prepared via a high energy planetary ball mill. J Alloys Compd. 2007;432(1-2):103.

[42] Huang JY, Wu YK, Ye HQ. Ball milling of ductile metals.Mater Sci Eng A. 1995;199(2):165.

[43] Pei ZM, Cai XL, Wang KJ. Bronze powder preparation by high energy milling. Min Metall. 2011;44(20):77.

[44] Menapace C, Cipolloni G, Hebda M, Ischia G. Spark plasma sintering behaviour of copper powders having different particle sizes and oxygen contents. Powder Technol. 2016;291:170.

[45] Madavali B, Lee JH, Lee JK, Cho KY, Challapalli S, Hong SJ.Effects of atmosphere and milling time on the coarsening of copper powders during mechanical milling. Powder Technol.2014;256:251.