BA De-ma, MA Shi-ning, LI Chang-qing, XIONG Tian-ying. Investigation of Surface Nanocrystallization of 38CrSi Steel by SFPB[J]. Journal of Materials Engineering, 2006, 0(12): 3-7.
A nanocrystalline surface layer was fabricated on a quenched and tempered 38CrSi steel by using Supersonic Fine Particles Bombarding(SFPB).The microstructural evolution of SFPB-treated specimens under different processing conditions was characterized by using X-ray diffraction,scanning electron microscopy,transmission electron microscopy.The results showed that obvious grains refinement was observed and a nanocrystalline surface layer(grain size<100nm) was found after SFPB treatment.The thickness of nanostructured surface layer increased depending upon the treatment duration,but the grain size of the top surface layer varied slightly.For the sample peened for 240s,the average size of equiaxed nanocrystallites with random crystallographic orientations on the top surface layer was approximately 16nm.The average grain size in the nanostructued layer increased with an increase of the distance from the top surface layer.In the region about 25μm depth from the top surface,large numbers of cell structures with size of 80-100nm separated by dense dislocation walls were formed.Experimental analysis indicated that grain refinement can be attributed to the movement of dislocation.
CHENG Ju-qiang, LIU Zhi-xue, WANG Yuan-hui. Study on Microstructure and Impact Fatigue Properties of New Type Bainitic Steel[J]. Journal of Materials Engineering, 2006, 0(12): 8-10,15.
The microstructure and impact fatigue property of new type bainitic steel were studied by observation of microstructure and impact fatigue test at different heat treatment.The results showed that the microstructure of new type bainitic steel was bainitic ferrite and retained austenite at normalizing and low temperature tempering,the microstructure was martensite and retain austenite at quenching and low temperature tempering.The impact fatigue life at normalizing and low temperature tempering was longer than that at quenching and low temperature tempering.The behaviour of impact fatigue cracks propagation were expounded.The reason of the increase of the impact fatigue life at normalizing and low temperature tempering was discussed.
WANG Chao-sheng, ZOU Zheng-guang, GU Tao, LONG Fei. In-situ Synthesis of SiCw/Al2O3 Ceramic Composite Powder from Natural Kaolinite[J]. Journal of Materials Engineering, 2006, 0(12): 11-15.
SiCw/Al2O3 composite powders were prepared by in-situ synthesis from natural kaolinite and carbon black.The thermodynamics was studied and the formation mechanism of SiC whisker was also discussed.Characterization of the products synthesized at 1550℃ with the Ar atmosphere was analyzed by XRD and SEM method,which indicated that the SiC was presented whisker morphology with the diameter ≤200nm and length ≥5μm.The mechanism of the proceed was shown as follows: SiO gas phase appeared firstly,then carbon black and SiO formed SiC micro-crystalline particles by gas-solid reaction.More SiC particles were formed by the reaction between SiO and CO gases at higher temperature and deposited at SiC（111）crystal face to form whiskers.Mullite was reduced simultaneously and the structure of Al2O3 particles coated by SiCw was formed finally.
HUANG Jin, ZHANG Ren-yuan, WU Bin. Crystal Forms Transformation and Thermal Expansion Property of Polycrystalline Na2SO4/SiO2 Composite Phase-change Energy Storage Materials[J]. Journal of Materials Engineering, 2006, 0(12): 16-20.
Using X-ray diffraction,the crystal forms transformation of salt/ceramic（Na2SO4/SiO2） composite of phase-change energy storage materials,which fabricated by molten Na2SO4 spontaneous infiltrating porous ceramic preforms,were analyzed.Using difference dilatometer,the thermal expansion percentage was measured,and the influences of crystal forms transformation on thermal expansion property were discussed.The results showed that near the temperature point of 240℃ and 580℃,the thermal expansion coefficient curve had two abrupt peaks,which was induced by two compositions crystal forms transformation,and in the range from 800℃ to 900℃,the average thermal expansion coefficient was 32×10-6/℃.
CAO Xiu-hua, WANG Lian-shi, HU Jian-hua. Aqueous Tape-casting of X7R Ceramic Powder to Prepare Ni Electrode-multilayer Ceramic Capacitor[J]. Journal of Materials Engineering, 2006, 0(12): 21-23,39.
Ni electrode-multilayer ceramic capacitor(Ni-MLCC) was prepared by aqueous tape-casting of X7R with acrylic emulsion as binders.Viscosity properties and thermal stability of acrylic binders were investigated.Scan Electronic Microscope(SEM) was used to analysis microstructure of green sheets and Ni-MLCC.Electronic properties of Ni-MLCC were also tested.The results showed that(aqueous) acrylic binders had shear-thinning properties suitable for tape-casting of ceramic powders.And low decomposition temperature was another good property for preparing Ni-MLCC.The green sheets had smooth surface without defect.Ceramic powders were dispersed uniformly in green sheets.The electrode of Ni-MLCC had excellent continuity.
TIAN Gao-feng, JIA Cheng-chang, LIU Jian-tao, HU Ben-fu. Effect of Cooling Medium on γ′ Precipitates and Properties in FGH96 Alloy[J]. Journal of Materials Engineering, 2006, 0(12): 24-27.
The experiment that effect of cooling mediums on γ′ precipitates and properties in FGH96 alloy was carried out by using optical microscope(OM) and field emission scanning electron microscope(FESEM).The results showed that the γ′ precipitates formed were spherical in shape as-cooled or aged,the size of γ′ precipitates was the smallest using water cooling.The results of hardness test indicated that the highest hardness value of alloys was gained using water cooling,followed by oil cooling,and the lowest using salt bath cooling;the hardness value of aged specimen was maintained the same order to that as-quenched specimen.
MAO Xin-fu, LIU Xiao-wen, WANG Yu, FENG Hong-chao. Microstructure and Properties of Carbon and High-speed Steel in Friction and Flash Welded Joint[J]. Journal of Materials Engineering, 2006, 0(12): 28-31.
Incompatible metallic cut cutter made from 45 and W18Cr4V was connected by friction or flash welding.The microstructure and properties in welding joint were compared and analyzed.Together with the reason of lower strength and fracture toughness were investigated in the soldering seam zone of the flash welded joint.The excellences of the friction welding and joint formation were illustrated.The optimal welding parameters were given for friction welded joint.The results showed that friction welding of 45 and W18Cr4V cut cutter improved the microstructure and properties in soldering seam zone of welded joint.
LIN Qi-lang, LI Tie-hu. Impregnating Pitch of Carbon-carbon Composites[J]. Journal of Materials Engineering, 2006, 0(12): 32-34,49.
Rheological properties and the impregnating performance of three pitches,including terephthalic aldehyde-modified pitch,and optical textures of resultant carbon-carbon composites,were studied.The results showed that the impregnating performance of pitch became good,and anisotropic unit size of the optical textures got large with improvement of rheological properties and decrease of quinoline insoluble(QI) content.Moreover,the impregnating efficiency of the modified pitch,indicated by densification degree of carbon-carbon composites,was much higher than those of the unmodified pitches during first two impregnation/carbonization cycles.
LIU Sheng-lin, SUN Dong-bai, FAN Zi-shuan, WANG Guo-gang, YU Hong-ying, MENG Hui-min. Microstructures and Erosive Wear Properties of Plasma Clad Fe Alloy Coating[J]. Journal of Materials Engineering, 2006, 0(12): 35-39.
Using Fe alloy powders as raw materials,coating was made on 1Cr18Ni9Ti steel substrate by plasma arc cladding.The microstructural morphology and the phase structure were studied in detail.The properties of microhardness and erosion resistance of coating were investigated.The characterizations of microstructure and surface morphology of coatings were analyzed by SEM.The results indicated that Fe alloy coating showed better properties not only in hardness but also in resistance of erosion than that of stainless steel substrate.Microhardness reached to 550,about 2 times that of stainless steel substrate.Erosion rate reduced about half for conventional 1Cr18Ni9Ti and 0Cr13Ni5Mo steel.
ZHANG Xiao-yun, ZHAO Sheng-hua, TANG Zhi-hui, YU Bo, LIU Ming, LIU Ming-hui. Effect of Surface Treatment on Galvanic Corrosion Between TC21 Titanium Alloy and Aluminium Alloys and Steels[J]. Journal of Materials Engineering, 2006, 0(12): 40-45,60.
The susceptibity to galvanic corrosion of TC21 titanium alloy and aluminum alloys and steels were studied by measuring current density of couples.The results indicated that it was easy to produce the serious galvanic corrosion between TC21 titanium alloy and aluminum alloys and steels.TC21 titanium alloy was prohibited to contact with aluminum alloys and steels directly.There was a low sensitivity to the galvanic corrosion between anodized titanium and anodized aluminum alloys.The galvanic corrosion behavior has relationship with the chemical compositions of steels.The anti-corrosion property can be high by anodizing for titanium alloy and plating Cd or Cd-Ti for steels.It is necessary to protect for aluminum alloys or steels when they are used with TC21 titanium alloy.
TONG Chang-qing, CHENG Lai-fei, ZHANG Li-tong, XU Yong-dong. Processing and Characterization of Multi-phase Matrix C/SiC-(W-C) Composite[J]. Journal of Materials Engineering, 2006, 0(12): 46-49.
A multi-phase matrix C/SiC-(W-C) composite was prepared by combined chemical vapor infiltration(CVI) technology with solution impregnation.The phase composition and microstructure of the composite were identified and characterized by XRD,EDS and SEM methods.Reaction mechanism was discussed primarily.The W-C was found to infiltrate the pores among fiber bundles,also among the filaments.The density and open porosity of the prepared C/SiC-(W-C) composite were 3.4g/cm3 and 11%,respectively.
ZUO Yi, LI Yu-bao, HAN Jin, CHEN Shi-tu, YANG Wei-hu, WU Lan, WANG Hua-nan. Characterization on Interface of n-CHA/HDPE and n-CHA/gHDPE Composite for Biomaterials[J]. Journal of Materials Engineering, 2006, 0(12): 50-53,57.
Two functionalized biomaterials were prepared in solution system by a new method at normal atmosphere.They were nano-carbonate hydroxyapatite reinforced high density polyethylene composite(n-CHA/HDPE) and n-CHA reinforced maleic anhydride grafted high density polyethylene composite(n-CHA/gHDPE).The interface of composites was analyzed in terms of burning test,TEM,IR,XRD and Molau testing.The results showed that n-CHA/HDPE composite was simple mechanical mixed,but n-CHA/gHDPE composite had stable interface connection based on the chemical bonding as esterification and hydrogen bonding formed between the two phases.
LI Shu-bo, WU Kun, ZHENG Ming-yi, XIONG Shou-mei. Effect of Extrusion on Mechanical Properties of AZ91 Cast Magnesium Alloy[J]. Journal of Materials Engineering, 2006, 0(12): 54-57.
The microstructure and mechanical properties of AZ91 magnesium alloy before and after extrusion were investigated.The results showed that tensile strength and ductility of extruded AZ91 alloy were greatly enhanced compared with the sample of as-cast AZ91 duo to grain refinement.Obvious yield phenomenon can be observed at true stress-strain curve of compression of extruded alloy as the result of twinning.The flow stress was strongly influence by the grain size.Flow stress of as-extruded AZ91 alloy were higher than that of the as-cast alloy at room temperature,but the flow stress as-extruded alloy was obviously decreased with the increase of deformation temperature.
QIAO Bin, YANG Jian-ming. Effect of Annealing on Properties of Electrodeposited Nanocrystalline Ni-Mn alloys[J]. Journal of Materials Engineering, 2006, 0(12): 58-60.
The nanocrystalline Ni-Mn alloys were prepared by the method of pulse electrodeposition.Microhardness and tensile strength of nanocrystalline Ni-Mn alloys were determined before and after annealing.The results showed that the microhardness and tensile strength of nanocrystalline Ni-Mn alloys were slightly increased after annealing.The effect of annealing treatment on the properties of nanocrystalline Ni-Mn alloys was discussed.
GAO Yuan, XU Zhong. Study on Improving Wear-resistance of Steel by Plasma Chromizing and Compound Strengthening[J]. Journal of Materials Engineering, 2006, 0(12): 61-64.
At first,plasma chromizing was engaged in cheaper material Q235 and 45 steel surface and the high chromized layer content were formed on the surface of these steels.The chromized layer contained more than 40%(mass fraction) of chromium. After plasma carburizing,the carbon content would be more than 2.8%(mass fraction),the carbides were very fine and distributed uniformly.These was no eutectic carbides in this kind of layer.The hardness on the surface after such compound strengthening was more than HV1800.Compared to the steel GCr15,the wear-resistance was increased about 7-times.
