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2016 Vol. 26, No. 06
Published: 2016-12-10
1
Microstructure and mechanical properties of welding zones of diamond saw blade
LUO Xi-yu，，XU Yan-jun， ，ZHANG Guang-ning， ，SHEN Xiang，，LIU Yi-bo，
DOI: 10.13228/j.boyuan.issn1006-6543.20160108
The transverse section division of welding seam， morphology， microstructure， composition and phase， hardness and bending strength of laser welding and brazing were analyzed， the samples were from butt-welded steel matrix and powders sintering segments of diamond saw blade. The cause of the laser welding pores was also stated. Results show that the fine-arrangement column grain and residual pores exist in the laser welding melting zone with the hardness varies linearly； while bi-phase structure， obvious dendritic structure and no cracks and pores exist in the brazing melting zone with low hardness. Acicular martensite appears in the laser welding heat-affected zone (HAZ) of steel side， while in the brazing， there is no HAZ caused by phase transition in the steel side. With specific proportioning system， there is also no HAZ caused by solid phase transition in the cutter head transition layer of laser welding and brazing segments， which remains powder sintering microstructure. The bending strength of laser welding and brazing seam are 1 175 MPa and 983 MPa， respectively， both higher than the overseas security strength requirements. The bending strength of laser welding has relatively large fluctuations， which is closely related to residual pores.
2016 Vol. 26 (06): 1-7 [
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Fabrication and properties of W-Cu functionally graded materials by tape calendaring method
SHEN Xiao，，CHENG Ji-gui，，LI Jian-feng，，CHEN Wen-chao，，WEI Chen-long，，LUO Lai-ma，，WU Yu-cheng，
DOI: 10.13228/j.boyuan.issn1006-6543.20150112
With tungsten powder and electrolytic copper powder as raw materials and PVB as the binder， W-Cu green tapes with different Cu contents (W-25%Cu， W-50%Cu， W-75%Cu， mass percent) were prepared by a tape calendaring method. Green W-Cu graded tapes were obtained by laminating the three W-Cu tapes together， and were subsequently sintered in H2 atmosphere to form W-Cu graded samples. Influence of the binder content on the green tapes was investigated. The formability， microstructure and physical properties were also investigated to evaluate the effect of processing conditions on the sintered W-Cu graded samples. The results indicate that W-Cu composite materials with layered structures can be successfully fabricated by a process based on tape calendaring and lamination. The binder content has an obvious effect on the density and properties of the W-Cu graded materials， and the green tapes with 6% (mass percent) binder show better formability and lower porosity. The W-Cu composite materials with layered structures sintered at 1 150 ℃ have a relative density of 93.11%. The resultant W-Cu graded materials have excellent physical and mechanical properties.
2016 Vol. 26 (06): 8-14 [
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15
Preparation and electrochemical properties of α-MnO2
LI Zhe， LI Tao
DOI: 10.13228/j.boyuan.issn1006-6543.20160003
Electrode material of MnO2 microspheres were synthesized via a simple liquid phase co-precipitation method by using K2S2O8 and MnSO4·H2O as raw material. The products were characterized by XRD and SEM. Results show that the α-MnO2 in tetragonal system with obvious nanothorn structure are obtained under the conditions of pH value of l，reaction temperature of 60 ℃ and reaction time of 22 h. The obtained α-MnO2 was then applied as the electrode material for supercapacitors， with 6 mol/L KOH as electrolyte solution， the electrochemical characterization was carried out using galvanostatic charge-discharge cycling， cyclic voltammetry and impedance spectroscopy. Its specific capacitance is 156.0 F/g at the scanning rate of 5 mV/s.
2016 Vol. 26 (06): 15-19 [
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20
Effect of silicon on the properties of iron-based magnetic powder cores
XU Lin-hao， ，ZHANG Hong-ping， ，ZHAO Dong-liang， ，DU Zhao-fu， ，YU Hai-chen
DOI: 10.13228/j.boyuan.issn1006-6543.20150115
The effects of silicon on the properties of iron-based magnetic powder cores were analyzed from hysteresis loop， loss， permeability and DC-bias. The results show that， the saturation magnetic induction intensity of magnetic powder core decreases with the increase of silicon content， and the pure iron powder core has the maximum saturation magnetic induction intensity. The loss of magnetic powder core decreases with the increase of silicon content， and the pure iron powder core has the highest loss， while the FeSi6.5 has the lowest. The permeability of pure iron powder core is higher than that of silicon-iron magnetic powder core， but it slowly rises with the increase of silicon content. The stability of DC-bias characteristic of magnetic powder core decreases with the increase of silicon content.
2016 Vol. 26 (06): 20-23 [
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24
Effect of volume ratio of SiC with different particle sizes on microstructure and tensile properties of SiCp/Al composites
XIE Rui，LI Ping，LIU Guo-kai，MA Jun-lin，XUE Ke-min，HE Peng
DOI: 10.13228/j.boyuan.issn1006-6543.20150114
In order to study the influence of volume ratio of SiC with different particle sizes on the microstructure and tensile properties of SiCp/Al composites， the mixtures of SiC particles with pure Al powder were fabricated into 10% SiCp/Al (volume percent) composites by high pressure torsion (HPT) method. The particle size of SiC particle is 3.5 μm (small) and 7.0 μm (large)， respectively， and the volume ratio of the small and large SiC particle is 4∶1， 1∶1 and 1∶4. The effects of SiC volume ratio on the microstructure and tensile properties of SiCp/Al matrix composites were studied by optical microscope， universal testing machine and scanning electron microscope. Results show that， with the increase of torsion radius， the distribution of SiC particles is more uniform and the particle agglomeration and segregation phenomenon decreases. The sample has the best performance when the volume ratio of small and large size SiC particle is 1∶1. The sample has the best elongation of 14.3% and the highest relative density of 99.1%. The tensile fracture of composite is ductile fracture.
2016 Vol. 26 (06): 24-29 [
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30
Study on the microstructure evolution of Cu60Cr40 alloy during microwave sintering
DONG Zhong-qi，YIN Su-hua，GAI Guo-sheng
DOI: 10.13228/j.boyuan.issn1006-6543.20150111
The Cu60Cr40 alloy was prepared using mechanical alloying， cold pressing and microwave sintering. The phase composition and microstructure of the Cu60Cr40 alloy were analyzed by XRD and SEM， respectively. The microstructure evolution rule of Cu60Cr40 alloy was investigated during the microwave sintering. Results show that， the microstructure of Cu60Cr40 alloy powder and cold pressed blank is lamellar. With the increase of sintering temperature， the microstructure of the Cu60Cr40 alloy transforms from laminar into short rod ball or ball grains， the grain boundary gradually becomes obvious， the porosity is reduced， and the density increases， the sintering process changes from solid phase sintering into liquid phase sintering.
2016 Vol. 26 (06): 30-34 [
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35
Study on properties of W-Ni-Fe alloy for high speed precision cutting by PCBN tool
ZHANG Yan，XIA Zhi-hui，XU Dong-ming
DOI: 10.13228/j.boyuan.issn1006-6543.20150106
The high-speed precision cutting experiment was conducted on W-Ni-Fe alloy using PCBN cutting tool. The failure and wear mechanism were analyzed by observing the rake and flank face of the cutting tool. Meanwhile， the cutting performance of PCBN tool when cutting W-Ni-Fe alloy was studied from the aspects of CBN contents， tool parameters and surface roughness. Results show that， the PCBN tool with high CBN content and large tip radius presents a longer life， and good surface quality is obtained in the condition of high cutting speed， low feeding rate and low cutting depth. The wear mechanism of W-Ni-Fe alloy in high speed precision cutting of PCBN tool is mainly composed of adhesive wear， diffusion wear， local peeling， oxidation wear， chipping wear and multiple results of them.
2016 Vol. 26 (06): 35-40 [
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41
Study on mechanical properties of ultra light aluminum sponge
WANG Zhan-guang，ZHEN Ying-hong，PENG Kai-qi，WANG Yang
DOI: 10.13228/j.boyuan.issn1006-6543.20150105
The aluminum sponge with porosity of 92%-98% was prepared by the combined method of complex model casting and seepage flow techniques， and the flammable polyurethane foam ball was employed as filling material. The mechanical properties of aluminum sponge were investigated. The results show that the compression curve of aluminum sponge is approximately divided into three stages： linear elastic stage， platform stage and densification stage. The pore structure is easy to be damaged due to its thin pore edge， and the yield strength of aluminum sponge decreases rapidly with the increase of porosity. The energy absorption curve of aluminum sponge is approximately linear， and the energy absorption efficiency at the platform stage is between 60%-80%.
2016 Vol. 26 (06): 41-45 [
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46
Effect of sintering temperature on the properties of biomedical titanium matrix composites
FAN Xing-ping，YANG Cheng
DOI: 10.13228/j.boyuan.issn1006-6543.20150104
Biomedical titanium matrix composites were fabricated by powder metallurgy method with titanium and hydroxyapatite (HA) powder as raw materials. The influence of different sintering temperature (1 200 ℃， 1 300 ℃ and 1 400 ℃) on microstructure， phase transformation， densification and compressive strength were studied. The results indicate that the composites exhibit high mechanical properties and good microstructure at proper sintering temperature. The HA has decomposed and reacted at 1 200 ℃， moreover， the microstructure of the composite material is loose. The density increases and the microstructure grows coarse with increasing sintering temperature， meanwhile， a large number of TiP and CaTi4(PO4)6 brittle phases form， which decreases the compressive strength of the composites.
2016 Vol. 26 (06): 46-49 [
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50
Effect of pre-deformation on heat treatment microstructure of FGH97 PM superalloy
HAN Shou-bo，，Lü Ri-hong，ZHANG Ying，，SUN Zhi-kun，，LI Ke-min，，HUANG Hu-bao，，LIU Ming-dong，，ZHANG Yi-wen，
DOI: 10.13228/j.boyuan.issn1006-6543.20160098
During the production and processing process， local surface pits usually occur on FGH97 PM superalloy products due to improper operation. The FGH97 alloy product with this kind of defects was tested and analyzed. The abnormal grain coarsening was found at the deformation zone caused by external force. Thermal simulation experiments were carried out to verify the effect of pre-deformation on heat treatment microstructure of FGH97 alloy. Results show that abnormal grain growth appears during heat treatment when the deformation of FGH97 alloy reaches the critical deformation， resulting in non-homogeneous microstructure， thereby affecting the performance and application of the alloy. It is advised that operation specification should be strictly abided to avoid local deformation.
2016 Vol. 26 (06): 50-54 [
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Research progress of discontinuous phase hybrid reinforced metal matrix composites
LI Jian-yun，XIE?Jing-pei，，WANG?Ai-qin，，ZHU Peng-fei
DOI: 10.13228/j.boyuan.issn1006-6543.20150108
The research situation of discontinuously reinforced metal matrix composites was discussed. Several kinds of preparation technology for discontinuous phase hybrid reinforced metal matrix composites were briefly introduced， including mixing casting， pressure casting， pressureless infiltration， spray deposition， powder metallurgy method， in situ reaction method， etc. Three common hybrid types were discussed， including particle and particle， short fiber and whisker (short fiber)， particle and whisker (short fiber). Properties and present research situation of those three types were reviewed. The existed problems of discontinuous phase hybrid reinforced metal matrix composites were proposed， and the future development was also forecasted.
2016 Vol. 26 (06): 55-61 [
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62
Control and analysis of powder metallurgy steel sintering process
TAN Zhao-qiang，WANG Hui，UlfEngstr?m
DOI: 10.13228/j.boyuan.issn1006-6543.20150098
The control of sintering process is very critical for PM technology. Bad control during sintering will cause inconsistence in dimension and mechanical properties of sintered parts， and even some failure issue， like oxidation， decarburization， carburization， blistering and sooting. With the higher requirement on the performance and cost of PM products， chromium with high hardenability and low cost becomes an interesting development of PM industry. However， Cr is easy to be oxidized， and has strict requirement on sintering atmosphere， so it is a challenge to the sintering process. With the development of sintering furnace and the wide use of nitrogen based protective gas， the sintering of PM part with Cr components in the net belt furnace has become a reality. Practical field experiences with sintering furnace atmosphere based on nitrogen and hydrogen mixed gas were given by utilizing a measuring system consisting of thermal couple， oxygen and CO probes. The cause and effect relationships for many common atmosphere-related problems were explored and solutions offered for corrective action， as well as the sintering requirement of materials with Cr were summarized.
2016 Vol. 26 (06): 62-66 [
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The design of drilling fixture for the pin hole on oil pump rotor shaft
SHANG Wei，ZHANG Ju-xiang，SHEN Xiao-ping
DOI: 10.13228/j.boyuan.issn1006-6543.20150072
Based on the basic structure of the oil pump rotor， the locating scheme and clamping scheme， the design of the locating and clamping device， and the design of ensemble structure of special drill jig in the production were presented. Aiming at the problem of lacking of generality on special drilling jig， the adjustable fixture， modular fixture and other solutions were put forward to ensure processing quality， improve machining efficiency， reduce processing time and reduce production costs.
2016 Vol. 26 (06): 67-70 [
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Research of leaching process and design of leaching equipment for NdFeB waste
HUANG Wei-ling，WANG Zhong-feng
DOI: 10.13228/j.boyuan.issn1006-6543.20160033
Since the low automation degree for retrieving rare earths from NdFeB waste and the large fluctuation of product purity at present， it is difficult to ensure safety of production process and running reliability， leading to low recovery index of rare earth. Recycling of rare earths from NdFeB waste relying on hydrochloric priority dissolution method was conducted. The purification process that greatly influences the rare earth leaching loss was experimentally studied， and the technical measures to improve the leaching rate were summarized. The NdFeB waste leaching process was also studied， and finally the extraction equipment was designed. The purity of rare earth recovery is stabilized， the recovery rate is improved， and the production cost is reduced， which has positive signification for automation and green production of NdFeB waste leaching process.
2016 Vol. 26 (06): 71-75 [
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