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2018 Vol. 28, No. 03
Published: 2018-06-10
1
Preparation and properties of boron-doped diamond electrode and its surface modification strategies
XU Yan-jun，，LIU Xue-quan，
DOI: 10.13228/j.boyuan.issn1006-6543.20170162
The boron-doped diamond （BDD） electrodes have been attracting much attention not only in electrochemistry， but also in fields such as functional materials， analytical chemistry， environmental science， biomedical or biological science， because of their superior properties such as high chemical stability， wide potential window，low background currents and an inert surface with low adsorption. The main preparation methods and basic properties of BDD electrodes were discussed， and surface modification strategies for BDD electrodes were also summarized.
2018 Vol. 28 (03): 1-7 [
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Ti6Al4V alloy powder prepared by electrode induction-melting inert gas atomization for 3D printing
YANG Qi-yun，WU Wen-heng，ZHANG Liang，HE Bei-bei，LONG Qian-lei，WU Kai-qi
DOI: 10.13228/j.boyuan.issn1006-6543.20170158
According to the characteristics requirements of metal powder materials used for 3D printing technology， Ti6Al4V alloy powder was prepared by vacuum electrode induction melting gas atomization （EIGA）. The effects of atomization pressure on the chemical composition， particle size distribution， particle morphology and flowability of the powder were investigated. Results show that the oxygen increment of Ti6Al4V alloy powder prepared by EIGA atomization technology is less than 0.02% （mass percent）. Some “satellite ball” and “hollow ball” particles form during the atomization process. With the increase of the atomization pressure， the average particle size of the powder gradually decreases and the powder flowability becomes worse. According to the requirements of 3D printing technology for powder properties， it is advisable to control the atomization pressure at 3.2-3.6 MPa.
2018 Vol. 28 (03): 8-12 [
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Study on microstructure and mechanical properties of 7075 aluminum alloy fabricated by selective laser melting
XIE Yan-jun，，YANG Huai-chao，WANG Xue-bing，KUANG Chun-jiang，，HAN Wei
DOI: 10.13228/j.boyuan.issn1006-6543.20170153
7075 aluminum alloy was prepared by selective laser melting technology. The effect of laser scanning speed on microstructure and mechanical properties of 7075 aluminum alloy was investigated. The results show that 7075 aluminum alloy prepared by selective laser melting technology is a single-phase solid solution with obvious cracks in it. Reducing the laser scanning speed can reduce the number of cracks， but the increasing internal stress can make the crack cracking degree increases. The contents of zinc and magnesium decrease with the decrease of laser scanning speed. Due to the directionality of the crack， the mechanical properties of the specimen in[z]direction are higher than those in[x]and[y]direction. The tensile strength， yield strength and elongation in[z]direction increase with the decrease of laser scanning speed， while the tensile strength in[x]and[y]directions decreases with the decrease of laser scanning speed.
2018 Vol. 28 (03): 13-18 [
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Effect of lubricant on properties of warm compacted water atomized iron silicon chromium powder
LI Wei-jian，LI Yuan-yuan
DOI: 10.13228/j.boyuan.issn1006-6543.20170169
Using the water atomized Fe-Si-Cr powder as the research object， different kinds and contents of lubricants were added into the water atomized Fe-Si-Cr powder for warm compaction. Through testing a series of physical properties such as density and insulation resistance of green compact， the influence mechanism of lubricant on the properties of green compact was analyzed， so as to determine the optimal lubrication adding mode. The results show that with the increase of lubricant content， the density， permeability and compressive strength of green compact increase first and then decrease. The insulation resistance and quality factor of green compact increase continuously. When the mass percent of lubricant is 0.5% of the powder， the magnetic ring has the best performance. At that same time， the different characteristics of magnesium stearate and EBS leads to the different performance contribution of the magnetic ring. When the mass ratio of magnesium stearate to EBS is 1∶3， the magnetic ring has the highest density（5.23 g/cm3）， permeability（29.0）and compressive strength（0.72 MPa）. However， when the mass ratio of magnesium stearate to EBS is 3∶1，the magnetic ring shows higher insulation resistance and quality factor.
2018 Vol. 28 (03): 19-23 [
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Effect of compaction pressure on microstructure and properties of mechanically alloyed Cu20Fe80 alloy during microwave sintering
WANG Bo，WANG Yang，DONG Zhong-qi，YIN Su-hua，FU Jun-wei
DOI: 10.13228/j.boyuan.issn1006-6543.20170004
Cu20Fe80 alloy was prepared by mechanical alloying， cold pressing and microwave sintering. The microstructure and phase composition of Cu20Fe80 alloy were analyzed by SEM and X-ray diffraction. The density and hardness of the alloy were determined， and the microstructure evolution during the preparation process was studied. The results show that the microstructure of Cu20Fe80 alloy is lamellar. With the increase of pressing pressure， the Cu20Fe80 alloy compacts gradually become dense， and the formability of the alloy increases. After microwave sintering， the microstructure of the alloy is also lamellar. With the increase of pressing pressure， the grain boundary becomes obvious， the porosity decreases， the density and the hardness increase.
2018 Vol. 28 (03): 24-28 [
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Microstructure and properties of SiCp/Al composites prepared by hot isostatic pressing
LI Shu-zhi，WANG Tie-jun，LIU Gui-rong，WANG Ling
DOI: 10.13228/j.boyuan.issn1006-6543.20160131
SiC particles reinforced aluminum matrix composites were prepared by hot isostatic?pressing?（HIP）. Microstructures and mechanical properties of the composites were studied. The fracture morphology and mechanism were analyzed and the thermal expansion coefficient of composites was also measured. The results show that the SiC particles in the composites agglomerate and form a hard SiC?skeleton after hot isostatic pressing. The tensile strength of 20%SiCp/6061Al （volume percent） composites reaches 304 MPa， while the tensile strength of 20%SiCp/2024Al （volume percent） composites reaches 276 MPa. The tensile strength of both composites reaches or exceeds the level of other preparation methods. The fracture mechanism of composites is the ductile fracture of the matrix， the cleavage fracture of SiC particles and the interface stripping between SiC and matrix. The thermal expansion coefficients of composites are compared with Turner and Kerner theory values. It shows that the numerical value of Turner model is closer to the experimental value.
2018 Vol. 28 (03): 29-33 [
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34
3D printing and gelcasting process of Ti-6Al-4V porous titanium bone
SHI Yong-liang，GUO Zhi-meng，LI Xiu-min，QI Cui-fen，YANG Xiao-cai
DOI: 10.13228/j.boyuan.issn1006-6543.20170112
The method for preparing porous titanium human bone model by 3D scanning， 3D printing and turning?mode was studied. The porous titanium bone model with an original size deviation of 0.5 mm was prepared by water-based gelcasting and vacuum sintering using Ti-6Al-4V powder as raw material and polyvinyl alcohol as pore former. Phase composition， shrinkage ratio， strength， porosity and pore structure change in the process of drying and sintering were investigated. The results show that， the body shrinkage is uniform in the gelcasting and vacuum sintering process， the radial shrinkage rate and axial shrinkage rate is 16.11% and 16.04%， respectively. The optimum performance is obtained at 1 200 ℃ for 2 hours. Under these conditions， the porous Ti has uniform honeycomb structure， pore size of 100-350 μm， micropore size of less than 10 μm， total porosity of 70.56%， open porosity of 65.60%， compressive strength of 194 MPa， and bending strength of 105 MPa. The structure and performance can both meet the requirement of making human skeleton.
2018 Vol. 28 (03): 34-39 [
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Effect of stretching temperature on microstructure and properties of rapidly solidified Mg-8Zn-0.5Y alloy
WANG Wen-le，JI Hui，ZHANG Peng-cheng
DOI: 10.13228/j.boyuan.issn1006-6543.20170147
SEM， XRD and EBSD were used to study the tensile fracture and microstructure evolution during deformation of rapidly solidified Mg-8Zn-0.5Y magnesium alloy， and the effect of stretching temperature on the microstructure and properties of the alloy was analyzed. The results show that the Mg-8Zn-0.5Y magnesium alloy is composed of quasi crystal Mg3Zn6Y and α-Mg， with the average grain size of 60 μm. With the increasing of stretching temperature， the tensile strength and yield strength of the magnesium alloy decrease， while the elongation increases apparently. The tensile fracture of the alloy is uneven at room temperature， and there are a large number of flat round dimples after tensile at 300 ℃. The volume fraction of the deformed microstructure in rapidly solidified Mg-8Zn-0.5Y magnesium alloy is 23% and its width is 2 μm at room temperature. As the stretching temperature increases to 300 ℃， the large angle grain boundary cellular structure with larger orientation difference and parallel distribution is formed in the grains.
2018 Vol. 28 (03): 40-43 [
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44
Study on the microstructure and properties of multi-component hard phase reinforced Mo2FeB2 based cermets
TAO Ze-xu，CONG Shan-hai，PENG Jia-jian，WANG Xiao-feng
DOI: 10.13228/j.boyuan.issn1006-6543.20170026
Mo2FeB2 based cermets were prepared by vacuum liquid phase sintering process using Mo， FeB and Fe powder as raw materials and adding various contents of WC， NbC， TiC. The effects of multi-component hard phase on the microstructure and properties of samples were studied by metallographic microscope， scanning electron microscope， energy spectrum analysis， X-ray diffraction， rockwell hardness test and wear test. The results show that the multi-component hard phase addition can refine the microstructure and dispersion strengthening， thus improving the hardness and wear resistance of cermets. When the mass percent of WC， NbC and TiC is 10%， 4% and 5%， respectively， the hardness and wear resistance of the samples are the highest.
2018 Vol. 28 (03): 44-47 [
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48
Experimental study on the application of nano-grade copper oxide powder in solar energy collector
ZHAO Jin-xiu，ZHOU Hong-xing
DOI: 10.13228/j.boyuan.issn1006-6543.20170105
The nano-sized copper oxide powder was added to the working fluid of heat collector， and the thermal conductivity of the aqueous solution was measured. Aqueous solution added with different mass fraction of nano CuO powder and pure water were used as working fluid of heat collector， the comparative experiments was carried out under the same solar radiation. The results show that the thermal conductivity of aqueous solution with nano CuO powder is significantly higher than that of pure water. The outlet temperature of the heat collector with 0.1%， 0.5% and 1.0% nano CuO powder added as working fluid is 4.7%， 6.6% and 4.9% higher than that with pure water as working fluid， respectively. The water temperature and heat storage capacity of the heat storage tank with 0.5% CuO nano-powder as heat collection medium are 15.2% and 29.8% higher than those with pure water as heat collection medium.
2018 Vol. 28 (03): 48-52 [
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Effect of particle size， grade and coating thickness of diamond coated with chromium film on thermal properties of diamond/Cu composite
HUANG Xia，，XU Yan-jun，，YIN Xiang，，LIU Yi-bo，，ZHENG Yong-xiang，，GE Ke，
DOI: 10.13228/j.boyuan.issn1006-6543.20170108
Diamond/Cu composites were prepared via infiltration method using diamonds with surface modification as raw materials. The effect of particle size， diamond grade and coating thickness on the composites’ thermal conductivity （TC） and thermal expansion characteristics were studied. The results show that the TC of diamond/Cu composites increases with diamond particle size and diamond grade. The TC is 787 W/（m·K） when the thickness of chromium coating on diamond is 210 nm， and 633 W/（m·K） when the thickness is 150 nm， which indicates that too thin chromium coating on diamond leads to the decrease of composite thermal conductivity. The coefficient of thermal expansion （CTE） of diamond/Cu composites is among （3.00～8.00）×10－6 K－1 at temperature between 30～200 ℃，and increases with temperature increasing.
2018 Vol. 28 (03): 53-56 [
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Preparation and mechanical properties of titanium matrix composites reinforced by graphene with Cu-coated for engines
WANG Li-jun
DOI: 10.13228/j.boyuan.issn1006-6543.20170148
The GNPs-Cu/Ti6Al4V composites were prepared by microwave sintering. The effects of copper plated GNPs on the microstructure and mechanical properites of Ti matrix composites were investigated. The results show that a layer of uniformly distributed copper particles is successfully coated on the surface of GNPs. The interfacial reaction between graphene and Ti matrix is serious， and TiC with particle size of 2-5 μm is easily generated. After copper coating， the TiC contents at the interface increase， and the new Ti2Cu phase is also generated. Compared to the GNPs/Ti6Al4V composites， the mechanical properties of the GNPs-Cu/Ti6Al4V are improved. The relative density， micro-hardness and compression strength of GNPs-Cu/Ti6Al4V are up to 95.48%， 468 HV0.1 and 1 406 MPa， respectively. At the same time， the wear mechanism changes from abrasive wear of Ti6Al4V matrix to adhesive wear of GNPs-Cu/Ti6Al4V composites.
2018 Vol. 28 (03): 57-60 [
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Effects of binder and warm compaction process on the properties of bonded NdFeB magnets
ZHONG Hong-hai，NI Di，CHENG Min，MU Hao-han，JIANG Yang
DOI: 10.13228/j.boyuan.issn1006-6543.20160137
In order to obtain high-performance bonded NdFeB magnets， NdFeB powders containing coupling agent and binder were warm compacted. The influences of pressure， temperature， the kind and the content of binder on the density and performance of bonded NdFeB magnets were explored in the temperature range of 70-110 ℃. The results show that the relations between compaction pressure and green density of the NdFeB powder with 0.5% coupling agent blending 0.6% binder （mass percent） is in accordance with HUANG Pei-yun’s equation with the compaction module of 3.57 MPa and the nonlinear exponent of 0.21. With the increase of temperature and pressure， the density and the maximum magnetic energy product of the bonded NdFeB magnets increase first and then decrease. The density of magnets decreases rapidly when the mass percent of the binder exceeds 1.0%. Using the identical temperature， pressure and the content of binders， the magnets with the addition of semisolid E44 binder has higher density than those with E51 and CYD. The bonded NdFeB permanent magnet material with the density of 6.7 g/cm3 and the maximum magnetic energy products of 104 kJ/m3 is obtained at 80 ℃.
2018 Vol. 28 (03): 61-66 [
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Research progress on preparation technology of spherical tungsten powder
ZHANG Ying-ying，，， ZHOU Wu-ping，WANG Tie-jun，WANG Xue-bing，，YANG Huai-chao，LIANG Jun-cai
DOI: 10.13228/j.boyuan.issn1006-6543.20160138
Spherical tungsten powder is the raw material of tungsten and tungsten alloys applying to 3D printing， porous materials， high density powder coating and other industries， the preparation method and process of spherical tungsten powder are concerned widely. The preparation methods of spherical tungsten powder at home and abroad were summarized. The characteristics of plasma spheroidization technology， the advantages and the research achievements were also introduced. By comparing the advantages and disadvantages of various preparation methods， the development trend of the preparation technology for spherical tungsten powder was put forward.
2018 Vol. 28 (03): 67-73 [
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Pollution reduction of powder metallurgy process
Lü Ze-yu，ZHANG Bo，Lü Zhu-ming，DIAO Xiao-hua，SUN Hui
DOI: 10.13228/j.boyuan.issn1006-6543.20170005
Powder metallurgy is a kind of metal forming technology that is energy saving， high efficiency and environment friendly. Powder metallurgy product has its special properties and application fields. With the further requirements for environmental protection， more and more attention has been paid to reduce pollution emission in powder metallurgy production. Taking one enterprise as an example， through the analysis of its pollution producing node in the process of powder metallurgy production， the way of its pollution prevention and control was found.
2018 Vol. 28 (03): 74-77 [
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Copyright © Editorial Board of Powder Metallurgy Industry
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Beijing Magtech
