ZHANG Ding-fei, ZHANG Hong-ju, DUAN Zuo-heng, QI Fu-gang, PAN Fu-sheng. Effect of Nd Addition on the Microstructure and Mechanical Properties of Mg-6Zn-Mn Magnesium Alloy[J]. Journal of Materials Engineering, 2013, 0(3): 1-5.
The microstructure and mechanical properties of as-extruded Mg-6Zn-Mn magnesium alloy with different Nd content were investigated by OM, XRD and tensile testing, respectively. It was found that the dendrite arm spacing of as-cast Mg-6Zn-Mn magnesium alloys was effectively decreased with Nd addition. Furthermore, the microstructure of Mg-6Zn-Mn magnesium alloys changed significantly after hot extrusion at 360℃ with Nd doped under extrusion ratios of 25. The Mg-6Zn-Mn magnesium alloy with 0.2% Nd shows the highest yield strength (about 250 MPa) and ultimate strength (above 300MPa) by tensile tests at room temperature.
YANG Ke, BAO Ye-feng. Erosion Wear Properties Research of Nitrogen-alloying Hardfacing Alloy[J]. Journal of Materials Engineering, 2013, 0(3): 6-9.
The nitrogen-alloying hardfacing alloy deposited layer was made through nitrogen instead of part of carbon and addition of the nitrogen-fixing elements of niobium,vanadium and titanium. The erosion tests were conducted at impact angles of 30, and the erosion wear mechanisms of hardfacing alloy were deeply analyzed. The results showed that spall of cutting and furrow were observed on surface of hardfacing alloy due to the impacting effect of high velocity water flow with sand. The predominant erosion wear mechanism of hardfacing alloy was micro chips by the cutting of erosion particles. A large number of fine carbonitride homogeneously precipitated out of martensitic matrix and grain boundary of hardfacing alloy, which can strengthen matrix metal and enhance hardness of hardfacing alloy. So the hardfacing alloy can be protected effectively from wearing of the erosion particles and the erosion wear resistance of hardfacing alloy was improved slightly. The wear characteristic of nitrogen-alloying hardfacing alloy was mainly included cutting, furrow and block desquamation at the place of carbonitride caused by the erosion particles.
DING Wan-wu, XIA Tian-dong, ZHAO Wen-jun. Effect Mechanism of TiAl3 on the Precipitation of TiC Particles in Aluminum Melt[J]. Journal of Materials Engineering, 2013, 0(3): 10-15.
The effect of TiAl3 on the precipitation of TiC particles in aluminum melt was studied when TiC and TiAl3 refining industry aluminum, and the mechanism was discussed using MEF3 and EPMA. The results show that TiC particles deposit quickly and have poor nucleation capability when TiC is used as the α(Al) nucleation phase only, but when TiC and TiAl3 common as the α(Al) nucleation phase, TiC particles deposit more and more slow. Even after long time, there was only a small amount of precipitation. It demonstrated better nucleation and higher resistance to grain refining fading. The reason is that TiAl3 increase the settlement resistance of TiC particles. The refinement effect fading of Al-Ti-C master alloy is caused by TiC precipitation.
LI Xiao-lin, CAI Qing-wu, YU Wei, ZHANG Heng-lei. Effect of Nitrogen Content on Precipitation Behavior, Microstructure and Properties of Cr-Mo-V Ultra-low Carbon Bainitic Steel[J]. Journal of Materials Engineering, 2013, 0(3): 16-21,26.
The morphology, size, distribution and chemical composition of precipitates and the microstructure of the ultra-low carbon bainitic steel with three different nitrogen contents were investigated by optical microscope (OM), scanning electron microscope(SEM), transmission electron microscope(TEM) and energy disperse spectroscopy (EDS). The results show that the microstructure of the steel with low nitrogen content is granular bainite, while the steel with high nitrogen content is granular bainite as well as some acicular ferrite. When the value of V/N is 3.4, the yield strength and ultimate strength increase by 231MPa and 95MPa, respectively, which is attributed to precipitation strengthening and fine-grain strengthening. Compared with the low nitrogen steel, the high nitrogen steel can obtain finer bainitic ferrite lathes, the number of precipitates increases and the size decreases. There are two kinds of different sizes of the nanometer-sized precipitate particles in matrix, one of these are vanadium carbonitride, which are the range of particle sizes from 10nm to 15nm and distributed within bainitic ferrite lathes. The other precipitates are smaller than 10nm enriched with Cr and V. It seems that this carbide can maintain the NaCl-type of structure.
GUO Fang, ZHANG Bao-guo, TIAN Xin-li, WANG Jian-quan, LI Fu-qiang, MAO Ya-tao. The Ultrasonic Vibration Processing of Oil Holes in Silicon Nitride Ceramic Plunger Sleeve[J]. Journal of Materials Engineering, 2013, 0(3): 22-26.
Finite element analysis showed that hot-press sintered silicon nitride ceramic plunger parts, which with good performances, could effectively improve the performance of the engine oil pump compared with the metal plunger. However, high hardness and brittleness of ceramic materials made it particularly difficult to process ceramics, especially in the processing of holes. Based on analyzing the processing methods of holes, the ultrasonic vibration processing technique was used to process holes in silicon nitride ceramic plunger sleeve, developed the process planning of sleeve, designed the special fixtures and tools, and then described the processing of inlet and outlet oil holes and lubrication holes in detail. Observed by digital microscope, the quality of holes machined by ultrasonic vibration processing is very perfect compared with the holes in metal plunger sleeve.
ZHANG Hong-xia, LIU Xiao-qing, YAN Zhi-feng, WANG Wen-xian, LI Yong-lian. Failure Analysis of 5A06 Aluminum Alloy Welding Joint Crack[J]. Journal of Materials Engineering, 2013, 0(3): 27-31,37.
The cracks near 5A06 aluminum alloy welding joint are analyzed. The metallurgical structure of base metal, welding joint and heat-affected zone are analyzed and the results indicate that organization is uneven and there is inclusion in the aluminum alloy, the precipitates are found in grain inner and boundary. The crack propagation character are analyzed and the results indicate that the crack originates from the inclusion of the specimen edge, and crack propagation along the grain boundary. Micro-fracture and macro fracture are analyzed by SEM and found that there are secondary cracks in the fracture, and the fracture was brittle fracture.
HUANG Dong-nan, YU Yang, NING Yu, MA Yu. FEM Simulation of an Al-alloy Profile with Non-symmetrical Cross Section During Porthole Extrusion[J]. Journal of Materials Engineering, 2013, 0(3): 32-37.
A mesh-reconstruction technology of welding-plane is introduced based on Deform-3D and Pro/Engineer software. Applying the technology, the metal flowing behaviors, temperature fields and mandrel stress distributions during the whole extrusion processes of two hollow profiles are analyzed. The results show that, the reconstruction technology is effective for simulation the whole extrusion process (including dividing, welding and forming) of hollow profiles with irregular cross section. The mesh-reconstruction technology provides a new method to investigate the metal flowing behavior, die structure optimization, temperature distribution of ingot, die stress during welding stage of porthole extrusion.
ZHOU Lei, SHI Qing-nan, WANG Jun-li, MI Hui, LIU Run. Texture and Mechanical Properties of Pure Copper Deformed by Asymmetrical Accumulative Roll-bonding[J]. Journal of Materials Engineering, 2013, 0(3): 38-41,50.
Pure copper sheets were prepared by Asymmetrical Accumulative Rolling Bonding(AARB) at room temperature. By optical microscopy, scanning electron microscopy(SEM) with electron backscattered diffraction(EBSD),X-ray diffractometer(XRD) with texture accessories and stretch mechanics performance tests, the microstructure,texture and mechanical properties of pure copper sheets by AARB were discussed. The results show that after six times of AARB, the grains of copper is refined by compression deformation and shearing deformation ,and the average grain size is refined to 5μm. Texture of sample main composed of {112}〈111〉, {123}〈634〉,{011}〈211〉 and {011}〈100〉. Yield strength and tensile strength of sample increase obviously.σ0.2 and σb got to 348MPa and 452MPa separately. The elongation of sample decreases to 2.3% after the second pass, and then it decreases a little with the rise of the equivalent strain.
WANG Xin, YIN Shu-chun, HE Lei, WANG She-bin. The Cleanliness and Modification Behavior of Nonmetallic Inclusions in 0.05C-0.3Si-2.0Mn-xCe Molten Steel[J]. Journal of Materials Engineering, 2013, 0(3): 42-50.
In order to develop high-level pipeline steel refining technology, the industrial pure iron and some elements were melted by vacuum induction furnace at 800Pa in Ar atmosphere. and refining by adding Ce element at 1873K, the 0.05 C-0.3 Si-2.0Mn(mass fraction/%) of four different Ce contents were obtained. The cleanliness of 0.05C-0.3Si-2.0Mn-xCe series liquid steel, modification behavior of inclusion and its mechanism were analyzed and discussed. The results indicated that when [Ce] content was 0.0052%-0.0374%, with Ce content increasing, [O] and [S] reduced remarkably, reaching to 0.0008% and 0.0010% respectively. With Ce content increasing,the yield ratio, elongation and impact energy of steel first increase then decrease, reaching to 92.9%,24.3%,276J respectively. The reason is that the angular inclusions of SiO2-MnS, strip shape and large volume inclusion of MnS were changed into about 1μm, even nanometer scale spherical-shape inclusion of rare earth sulfur oxide.
ZHAO Yan-ling, ZHOU Kai, CHE Wan-bo, XUAN Jia-ping, CHE Chun-yu. Numerical Simulation of Reinforced Particle Stress Concentration in Al-Si Alloy Rolling[J]. Journal of Materials Engineering, 2013, 0(3): 51-54,60.
In the rolling process of aluminum-silicon alloy, there was a problem of silicon grains stress concentration which results from the deformation resistance of silicon grain was bigger than aluminum matrix. Aiming at this problem, the finite element model of reinforcement particles is established in rolling and the stress and strain contours and curves of silicon grains and aluminum body are researched by the finite element procedures. The problem that the stress of reinforcement particles in rolling process can not be analyzed quantitatively by ordinary experiment is also solved. The results show that the strain of the aluminum matrix near the grains is greater than other parts of the Al matrix and far greater than the strain of silicon grain, which indicates the metal accumulation phenomenon appeared on the grains. The stress value of silicon grain is greater than aluminum matrix, which indicates stress concentration phenomenon appeared because of the accumulation of the metal near the grains. After the simulation, the feasibility of numerical simulation method and the accuracy of simulation results can be validated indirectly by the method of observing the feature of tensile fracture with the electron microscopy and analyze the energy spectrum.
QIANG Xiao-hu, ZHANG Hong-xia, WANG Yan-ping, FENG Li-bang. Structure and Adhesive Mechanism of Superhydrophobic Alumina Surface with High Adhesive Force[J]. Journal of Materials Engineering, 2013, 0(3): 55-60.
Alumina gel film was prepared by the sol-gel and dip-coating method using Al(O-sec-Bu)3 as a precursor. Then an alumina film with both superhydrophobicity and high adhesive force was fabricated by treatment procedures as heat, boiling water, and surface modification with PEI and STA. The chemical composition, morphology, structure, and wettability of the superhydrophobic surface were investigated by techniques as FTIR, FE-SEM, XRD, and contact angle measurement. Results show that the alumina surface is made up of the porous flowerlike structure coated with a layer of long hydrophobic alkyl chains. Water is expected to enter into the large scale grooves of the rough alumina surface, but it can not enter into the small scale ones. Consequently, the alumina surface shows both high contact angle and strong adhesion.
SHAO Ze-bin, CHEN Hai-tao, LANG Yu-ping, ZHU Xin-kun. Effect of Thermal Processing on the "Gold Dust" Defect of 430 Ferritic Stainless Steel[J]. Journal of Materials Engineering, 2013, 0(3): 61-66.
The relationship between the intergranular corrosion and "gold dust" defects on surfaces of 430 ferritic stainless steel was investigated. On the basis of the different hot rolling tests performed on Gleeble 3800 thermal mechanical simulation and simulated coiling test after deformation, a study was conducted in order to determine the effect of thermal processing on the intergranular corrosion of 430 ferritic stainless steel. The DL-EPR was introduced to measure the susceptibility to intergranular corrosion.The results showed that the 430 ferritic stainless steel sensitization happened in the process of hot rolling, then conduce intergranular corrosion during the pickling, eventually produced the "gold dust" defects after cold rolling. It is found that the intergranular corrosion sensitization could be effectively prevented with a combination of final rapid cooling (water cooling) at the final deformation temperature of 900-950℃.By the analysis of simulated coiling test results, the intergranular corrosion susceptibility of 430 ferritic stainless steel can be further avoided and eliminated by a treatment of 650-800℃.
SHU Jing, FENG Xiao-hui, ZHENG Li-na, SANG Xi-qin, WANG Dan-dan. Preparation and Sensitivity Behaviors of Chitosan-based Intelligent Hydrogels[J]. Journal of Materials Engineering, 2013, 0(3): 67-70,76.
Chitosan-based ternary intelligent hydrogels of pH/temperature-sensibility were prepared on the basis of chitosan/polyvinylpyrrolidone(CS/PVP)hydrogels with polyvinyl alcohol(PVA)introducing,using glutaraldehyde as crosslinking agent and ammonium ceric nitrate as initiator. The results indicated that the introduction of PVA increased the concentration of CS in the hydrogels significantly and made the temperature-sensitive grade increase. Especially, the hydrogels indicated obvious temperature-sensitivity at 35℃. Under the optimal conditions, that is, 6.25%PVA(mass fraction, compared to PVP), 5.1% initiator, 0.4% cross-linking agent, 80℃ and 6h, the maximum swelling ratio of hydrogels was about 1500%. Thermo-sensitive and pH-sensitive experiments showed that the hydrogels were of excellent thermo-sensibility and pH-sensibility. The chitosan-based ternary hydrogels were of four grades temperature-sensitivity and good pH-sensitivity with the abrupt change point at 2.0.
LI Zhuan, XIAO Peng, YUE Jing, XIONG Xiang. Wet Friction and Wear Properties of C/C-SiC Composites During Different Braking Speeds[J]. Journal of Materials Engineering, 2013, 0(3): 71-76.
Carbon fibre reinforced carbon and silicon carbide dual matrix composites (C/C-SiC) were fabricated by the combination of chemical vapor infiltration (CVI) with liquid silicon infiltration (LSI). The tribological behaviors of the C/C-SiC composite were investigated using an MM-1000 friction and wear tester, at different braking speeds under dry and machine oil lubricating conditions. The results indicate that the contact angle between C/C-SiC and distilled water is about 80.5°, which means the C/C-SiC are lipophilic materials. In the CD15W-40 diesel engine oil lubrication condition, with the brake speeds increasing from 3000r/min to 6000r/min, the coefficient of friction (COF) and linear wear of C/C-SiC reach the maximum value of 0.21μm/cycle and 1.1μm/cycle respectively, at 4000r/min. When the brake speeds are 5000r/min and 6000r/min, the COF and the linear wear are 0.17 and 0, respectively. C/C-SiC maintains a relatively high COF, smooth braking curves and lower wear rate in wet conditions, which can be used as candidate materials for wet clutch of new generation of construction machinery and heavy vehicles.
CHENG Yuan, YU Hong-ying, WANG Ying, MENG Xu, SUN Dong-bai. Effect of Strain Rate on Stress Corrosion Cracking of X80 Pipeline Steel[J]. Journal of Materials Engineering, 2013, 0(3): 77-82.
Stress corrosion cracking susceptibility of X80 pipeline steel was investigated in a simulated soil solution using slow strain rate tensile (SSRT) tests. The simulated soil solution was based on the chemical compositions of alkaline Gansu soil in northwest of China. The tests were conducted at different strain rates. The fracture surfaces and secondary cracks were observed using scanning electron microscopy (SEM). The results showed that strain rates had an important role on SCC of X80 steel in simulated soil solutions. Corrosion and mechanical factors have different influences during the SCC processes at different strain rates, which results in the variety of SCC. There was the highest SCC susceptibility at the strain rate of 1.0×10-6s-1. Combined effect of corrosion and mechanics leads to high SCC susceptibility. When the strain rates were lower than 1.0×10-6s-1, enough long corrosion time results in the corrosion of crack in this strain rate range. The crack propagation is restrained. Thus, slight decrease of SCC susceptibilities occurs. As the strain rates were higher than 1.0×10-6s-1, SCC susceptibilities were low obviously. In this high strain rates range, the mechanical factors have more effect on SCC than corrosion factors, which mainly lead to mechanical fracture of specimens.
YANG Tang, LIU Bing, WEN Feng, GUO Lu, ZHAO Ming-lu. Corrosive Wear Properties of Al-Mn Eutectic Alloy Reinforced by Al2O3 Particle[J]. Journal of Materials Engineering, 2013, 0(3): 83-89.
The metallographic structures of Al-Mn eutectic alloy and its composite were investigated by XRD and SEM. The mass loss, friction coefficient and wear trace of the samples were studied under three different kinds of friction conditions. And their properties of erosion resistance were analyzed by SEM and EDS. The results show that the shapes of brittle Al-Mn compounds are changed as Al2O3 particle is added. The mass loss and friction coefficient of the samples under corrosive liquid and abrasive condition are less than those under corrosive liquid condition, but higher than those under dry sliding condition. The pits of samples under corrosive liquid condition are more than those under corrosive liquid and abrasive condition, and the furrows of samples under corrosive liquid and abrasive condition are deeper than those under dry sliding condition by observing wear traces. As the particle size of abrasive increases, wear rates of erosion samples increase first and then decrease in 7m/s erosion speed, but decrease gradually in 3.5m/s. In addition, the mass of Al-Mn eutectic alloy samples increase after the erosion test under the 3.5m/s erosion speed and 0.15-0.212mm particle size condition.
TAN Yi, GUO Xiao-liang, SHI Shuang, DONG Wei, JIANG Da-chuan, LI Jia-yan. Research Status and Development of Metallurgical Method for Solar Grade Silicon (SOG-Si)[J]. Journal of Materials Engineering, 2013, 0(3): 90-96.
Purification polycrystalline silicon by metallurgical method is the only way for our country to escape the dependency of silicon feedstock, and to develop low-cast and environmental friendly process for SOG-Si. Since its emergence, metallurgical method has undergone three research surges. The third development is under the leading and promotion of our country's research and industry workers, obtaining considerable useful scientific theory and practical experience. In this paper, from the definition of metallurgical method, the basic theories of metallurgical method, including saturated vapor pressure principle, segregation mechanism and differences in mechanism of oxidation, are analyzed in detail; moreover, technologies and their progress derived from the mechanisms are presented. At the end, the trend of metallurgical method is forecasted.
