LI Ji-zhong, MA Zheng-bin, DONG Chun-lin, LUAN Guo-hong. Material Flowing Behaviors of Friction Stir Welding by Dissimilar Aluminum Alloys[J]. Journal of Materials Engineering, 2014, 0(6): 1-4.
Dissimilar aluminum alloys with two types of alternate arrangement were carried out for studying material transformation and flowing during friction stir welding for material flowing. The results show that two types of rippling intervals are formed on the surface of weld with perpendicular arrangement to weld line, in which the coarse rippling intervals contributes to the cyclical gradient fluctuating material in the traverse direction. In advancing side, the intensity of material flowing and mixture is higher than that of retreating side, and the marker materials keep consecutive distribution with basal zone in the retreating side. As a result of different deformation in the weld, the boundaries are clearly formed between shoulder affected zone, probe affected zone and base metal.
CHEN Lian-sheng, ZHAO Yuan, TIAN Ya-qiang, SONG Jin-ying, WEI Ying-li, YANG Dong. Low Carbon Si-Mn Q&P Steel Plasticity Enhancement Mechanisms and Microstructure Property[J]. Journal of Materials Engineering, 2014, 0(6): 5-10.
Low carbon Si-Mn steel was processed through intercritical insulation-quenching-partitioning. The plasticity enhancement mechanisms and organizational performance of the Q&P steel were studied by means of field emission scanning electron microscopy, X-ray diffraction and tensile tests. The results show that after intercritical insulation-quenching-partitioning, the steel demonstrates superior comprehensive mechanical property to traditional Q&P steel. Reasonable intercritical insulation time can reduce the secondary quenching martensite content in the organization, so as to ensure better plasticity. The content of retained austenite in the steel is 4.9% after Q&P processing. With the extension of the intercritical insulation time, the content of retained austenite in the steel first increases and then decreases after intercritical insulation-quenching-partitioning. When the steel is intercriticallly insulated at 720℃ for 1500s, and is then quenched and partitioned, the content of retained austenite in the steel reaches the maximum 7.3%, and the comprehensive mechanical property of the steel is the best.
LIU Ying, ZHANG Pin-fang, CHEN Lan-jun, ZHANG He, ZHANG Xin-ming, GENG Zhan-ji. Effect of Pre-precipitation on Localized Corrosion Properties of 2519A Aluminum Alloy[J]. Journal of Materials Engineering, 2014, 0(6): 11-17.
The influence of pre-precipitation on tensile mechanical properties, stress corrosion cracking and intergranular corrosion properties of 2519A aluminium alloy was studied. The mechanism was analyzed through microstructure observation by transmission electron microscope. The results show that for 2519A-T6 samples, pre-precipitation can improve localized corrosion resistance. Stress corrosion cracking time by constant load test increases from 1 day (no pre-precipitation) to 9 days (pre-precipitation). Maximum intergranular corrosion depth decreases from 220μm to 120μm while ultimate tensile strength still remains 400MPa. Localized corrosion properties of 2519A-T8 samples are improved by pre-precipitation. Cracking time prolongs from 10 days (no pre-precipitation) to 14.9 days (pre-precipitation). Maximum intergranular corrosion depth and its corrosion morphology remain unchanged while ultimate tensile strength of pre-precipitation T8-samples is decreased. Proper pre-precipitation can enhance the discontinuity and coarsening of precipitates in grain boundary for both T6 and T8 temper, in which is due to enhancement of localized corrosion resistance.
HU Qiao, ZHANG Min, LI Hai-fei, YIN En-huai, PANG Shu-jie, ZHANG Tao. Formation, Bio-corrosion Behavior and Mechanical Properties of Ti-Zr-Cu-Co-Sn-Si Bulk Metallic Glasses[J]. Journal of Materials Engineering, 2014, 0(6): 18-21.
Novel Ti87-xZr7.5CuxCo2.5Sn2Si1 (x=39,40,42, atom fraction/%) bulk metallic glasses without highly toxic elements Ni and Be as well as noble elements were synthesized by copper mold casting, and their glass-forming ability, thermal stability, bio-corrosion behavior and mechanical properties were studied. The results show that the Ti-Zr-Cu-Co-Sn-Si metallic glasses possess high glass-forming ability and thermal stability, evidenced by the critical diameters of 2-3 mm and large supercooled liquid region of 44-51K. The Ti-Zr-Cu-Co-Sn-Si metallic glasses exhibit high bio-corrosion resistance in phosphate buffered saline (PBS) at 37℃. They are spontaneously passivated with wide passive region and low passive current density of about 3×10-2A/m2. The corrosion resistance is enhanced with the increase in Ti content in the metallic glass. The Ti-based bulk metallic glasses possess high compressive fracture strength up to 2309MPa and low elastic modulus of 92-100GPa.
LI Yong-quan, XIE Fa-qin, WU Xiang-qing, YAO Xiao-fei. Effect of Temperature on Microstructures of Si-Al-Y Co-deposition Coatings on TiAl Alloy[J]. Journal of Materials Engineering, 2014, 0(6): 22-27.
Si-Al-Y2O3 co-deposition coatings on TiAl alloy were prepared by pack cementation processes at 1000, 1050, 1100℃ and 1150℃ for 4h, scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) were employed to investigate the surface morphologies, microstructures and phase constitutions of the coatings. The results show that the Si-Al-Y co-deposition coatings have multi layer structure. All the coatings are mainly composed of a TiAl2 and γ-TiAl inner layer, and an Al rich inter-diffusion zone; the phase constituents of outer layers and middle layers of the coatings change with increasing co-deposition temperatures. The outer layer of the coating prepared at 1000℃ for 4h is composed of TiAl3. However, the constituent phases change into TiSi2 in the out layer, and the middle layer is composed of (Ti, X)5Si4 and (Ti, X)5Si3(X represents Nb and Cr) for coating prepared at 1050℃ for 4h. The coatings prepared at 1100℃ and 1150℃ for 4 h have same layer structure, and (Ti, X)5Si4,(Ti, X)5Si3 phases are detected in the outer layer of the coating prepared at 1100℃, and (Ti, X)5Si3 phases are detected in the outer layer of the coating prepared at 1100℃. In the four kinds of (1000, 1050, 1100℃ and 1150℃) temperatures investigated, the coating prepared at 1050℃ for 4h have a denser and thicker layer, so it is selected for Si-Al-Y co-deposition.
WANG Bin, XUE Wen-bin, JIN Xiao-yue, WU Jie, HUA Ming, WU Zheng-long. Plasma Electrolytic Borocarburizing Treatment on Q235 Low-carbon Steel and Its Properties[J]. Journal of Materials Engineering, 2014, 0(6): 28-34.
Q235 low carbon steel was treated by plasma electrolytic borocarburizing (PEB/C) with the method of plasma electrolytic saturation.The morphology, structure and microhardness of borocarburizing layer on Q235 low-carbon steel were investigated. The electrochemical corrosion properties of Q235 steel before and after the PEB/C treatment were evaluated, and the tribological behavior of plasma electrolytic borocarburized Q235 low-carbon steel against GCr15 bear steel ball under different load was analyzed. The results show that the Q235 low-carbon steel forms a boride layer about 20μm thick after 330V and 30min PEB/C treatment. The boride layer mainly consists of Fe2B phase. The PEB/C treatment slightly improves the corrosion resistance of Q235 steel and significantly reduces the friction coefficient and wear rate of the Q235 steel against GCr15 steel ball. The friction coefficient and wear rate of PEB/C sample with a 5 N load are only 1/4 and 1/59 of that of the bare Q235 steel, respectively.
CHU Ya-jie, LI Xiao-quan, WU Shen-qing, XU Zhen-qin, DU Shun-yao. Influence of Hot Compression Deformation on Microstructures and Mechanical Properties of Welded Joints for AZ31 Magnesium Alloy[J]. Journal of Materials Engineering, 2014, 0(6): 35-39.
AZ31 magnesium alloy sheets were welded by manual TIG (tungsten insert gas) welding method with the same welding wire as filler material. The welded joints were compressed at 250,300,350,400℃ and strain rates of 0.001s-1 by a vacuum hot pressing furnace and a specially designed mold clamp. Microstructures and mechanical properties of welded joints with hot compression were analyzed by tensile test, optical metallographic microstructure (OM), scanning electronic microscopy (SEM). The results show that the tensile strength and elongation of the welded joint increase with the increasing temperature of hot compressing. The welded joint show the maximum tensile strength of 228MPa and elongation of 10.2% at 350℃, but lower at 400℃. The recrystallization phenomenon of joint is more and more obvious with the increasing deformation temperature in the process. Many dynamic recrystallization cores and small grains appear at 350℃ and the average grain size decreases from about 46μm to 16μm. As the temperature increases, the number of dynamic recrystallization grain is gradually increased. The grain size has grown up at 400℃, the average grain size is 26μm and evenly distributed.
WU Jiang-yu, HE Zi-ying, LI Xiu-hui. Preparation and Performance of Water Swellable Rubber Based on Modified Superabsorbent Resin[J]. Journal of Materials Engineering, 2014, 0(6): 40-44.
Superabsorbent resin (SAR) was synthesized from comonomers acrylic acid (AA), 2-acrylamide-2-methylpropane sulfonic acid (AMPS) and diallyldimethylammonium chloride (DADMAC). Modification of SAR was performed using butyl acrylate (BA) as the hydrophobic modifier. Water swellable rubber (WSR) was then prepared with SAR and nitrile butadiene rubber (NBR) through physical blending method. The effects of P(AA/BA) content on the water absorbency of SAR and WSR and on the mechanical property of WSR were investigated. The results show that the water swelling ratio of SAR decreases only 8.49% when the P(AA/BA) content reaches 33.3% of SAR (mass fraction, the same below). When the P(AA/BA) content is 23.1%, WSR achieves the best performance in terms of tensile strength, breaking elongation, and water absorbency, showing a low mass loss of 5.8%. The introduction of P(AA/BA) enhances the compatibility of SAR with NBR and improves the practical performance of WSR.
WANG Huai-yuan, LIN Shan, ZHANG Shuai, YANG Shu-hui, ZHU Yan-ji. Biomimetic Design and Tribological Properties of Porous Lubricating Wear-resistance CF/PTFE/PEEK Composite[J]. Journal of Materials Engineering, 2014, 0(6): 45-50.
Using molded-leaching and high temperature vacuum melting technologies, the self-sweating lubrication wear-resistance porous CF/PTFE/PEEK composites were prepared. The effects of porogen (NaCl), PTFE content and the distance between each of two CF layers on porous PEEK composite material structure and tribological behavior were investigated. The results show that the porous CF/PTFE/PEEK composite material contains 20% (mass fraction,the same below) PTFE, 30% NaCl and the distance between two CF layers of 0.4mm has the lowest friction coefficient and wear rate. When load is 200N, comparing with classic CF/PEEK composites, the friction coefficient of the porous CF/PTFE/PEEK composite decreases 9 times and wear resistance increased by 25 times. PTFE in the porous composites can form continuous transfer films which reduce the friction coefficient, and the porous structure can store certain lubricant grease which results in stable lubricating oil film during sliding. Thereby, above mentioned advantages significantly reduce the friction and wear rate of porous sweating composite. In addition, the carbon fiber cloth shows the role of skeleton supporting effect, and also cooperating with PTFE, NaCl to improve the wear resistance of porous PEEK composite material.
DONG Jian-min, LI Jia-rong, MU Ren-de, ZHAO Jin-qian, SHI Zhen-xue, LIU Shi-zhong. Effect of High Temperature Heat Treatment on Elements Interdiffusion Behavior and Stress Rupture Characteristics of DD6 Single Crystal Superalloy with Thermal Barrier Coatings[J]. Journal of Materials Engineering, 2014, 0(6): 51-55.
Thermal barrier coatings were deposited on DD6 single crystal superalloy substrate by electron beam physical vapor deposition (EB-PVD), and then the specimens with coatings were subjected to heat treatment at 1100℃ in the air for 50 hours and 100 hours respectively before stress-rupture testing under the conditions of 980℃/250MPa. The elements interdiffusion behavior, microstructure and stress rupture characteristics were investigated after stress-rupture tests. The results show that elements interdiffusion between bond coat and the alloy occurs after high temperature heat treatment at 1100℃. DD6 alloy is rich of Cr, meanwhile Re, Nb, Mo and Ta diffuse from alloy to bond coat. The number of TCP and γ' phase coarsening extent increase with the heat treatment time. There is little effect on the stress rupture mechanism of DD6 single crystal superalloy with thermal barrier coatings, the stress rupture characteristic is dimple fracture.
LI Qi, WANG Xian-cheng, CAI Zhi-hai, DI Yue-lan, HE Xing. Influence of Loads on Tribological Property of Heavy Vechicle Engine Piston Ring-cylinder Liner[J]. Journal of Materials Engineering, 2014, 0(6): 56-61.
Working conditions of piston ring-cylinder liner mate were simulated by SRV test rig. Friction coefficient and mass loss of mate under different static loads and vibration loads were tested. SEM-EDS were used to analyze wear marks and chemical composition. Wear mechanisms of piston rings-cylinder liners were researched. The results show that friction coefficient of mate decreases and mass loss increases with static load increasing. The main wear mechanism of mate is abrasive wear. The mechanism changes to abrasive wear and adhesion wear under 400N. Friction coefficient of mate appears cyclic change when loads alternate under low and moderate strength. The main wear mechanism of mate is abrasive wear. Friction coefficient of mate keeps stable under high strength. The wear mechanism of piston rings is comprehensive abrasive, adhesion and fatigue wear. The wear mechanism of cylinder liner is comprehensive abrasive, adhesion wear. Mass loss increases with strength of vibration load increasing.
NI Xin-ye, LI Ai-jun, ZHONG Ping, LIN Tao, XIONG Xin-bo, GU Wei-dong. Effect of Different High Temperature Treatment Processes on Biocompatibility of Carbon/Carbon Composites[J]. Journal of Materials Engineering, 2014, 0(6): 62-67.
The effect of the toxic substances of carbon/carbon composites by different graphitization treatment times and their impact on osteoblast growth was studied. The results show that prolonging heat treatment can remove toxic substances As and Pb, and reduce Hg, Cd, Al, and other toxic contents. In addition, osteoblasts slowly grow by short time(4,8h) high-temperature treatment and show an obvious toxic effect, but osteoblasts grow well on the carbon/carbon composite surface by long time(12,16h) high-temperature treatment.Thus, extended heat treatment can significantly improve the biocompatibility of the carbon/carbon composites.
DU Nan, YE Chao, TIAN Wen-ming, ZHAO Qing. 304 Stainless Steel Pitting Behavior by Means of Electrochemical Impedance Spectroscopy[J]. Journal of Materials Engineering, 2014, 0(6): 68-73.
Pitting behavior of 304 stainless steel in 3.5% (mass fraction) NaCl solution was investigated by dynamic potential electrochemical impedance spectroscopy (DEIS) and time scan electrochemical impedance spectroscopy (TSEIS). The results of DEIS show that metastable pits emerge at the potential (0.02V) which is more negative than the pitting potential (0.15V), and the generation and passivation of metastable pits are stochastic. The steady pitting potential which got from DEIS is negative than breakdown potential which got from dynamic potential polarization by 0.05V. The results of TSEIS indicate that pitting nucleation can happen just when the thickness of passivation film has been reduced to some extent. It reveals the characteristics of the structure of electric double layer and passivation film by analyzing element parameter of the equivalent circuit.
REN Wei-peng, LI Qing, XIAO Cheng-bo, SONG Jin-xia, HE Li-min, HUANG Guang-hong, CAO Chun-xiao. Oxidation Behavior of CoCrAlY Bond Coating for Thermal Barrier Coating on DZ466 Super Alloy at 1050℃[J]. Journal of Materials Engineering, 2014, 0(6): 74-78.
CoCrAlY bond coating and Y2O3 partially stabilized ZrO2 ceramic coating were deposited by electron beam physical vapor deposition (EB-PVD), and the cyclic oxidation behavior of the samples were measured at 1050℃. X-ray diffraction, scanning electron microscopy and electron probe microanalysis were employed to examine the microstructure. The results show that the thermal barrier coating (TBC) remains intact after exposure at 1050℃ for 1500h (31 cycles). As-deposited CoCrAlY bond coating consists of β-CoAl phase and γ-Co solid solution, thermally grown oxide (TGO) appears at the interface of bond coating and ceramic coating during exposure at 1050℃ and meanwhile degradation of bond coating occurs, β-CoAl phase gradually transforms into γ-Co solid solution. Oxide pegs form at the TGO/bong coating interface due to reactive elements effect after oxidation for 1200h. Rumpling of TGO induces micro-cracks at interface of TGO/ceramic coating, and the micro-cracks propagate along the interface. Thickness growth mode of TGO follows staged parabolic law, the initial oxidation rate constant is about 6.1×10-14cm2/s, after exposure for 400h, the oxidation rate constant decreases to 3.5×10-14cm2/s.
ZHANG Ren-yong, WANG Xia, SHI Dai-yan, CHEN Yong-bin, JU Lan, ZHANG Jin-zhong. Expansion Property of 316L Stainless Steel Pipe[J]. Journal of Materials Engineering, 2014, 0(6): 79-83.
The radial expansion experiment of 316L stainless steel pipe with 9% expansion ratio was performanced by top-down expandable craft, and contrasted with the mechanical property before and after the expandable deformation. The results show that the characteristics of 316L stainless steel pipe, including about 3.6% of the length decreases,4.4% of the wall thickness reduction,and the degree of uneven deformation aggravates. The Brinell hardness and tensile strength increase obviously, but the elongation and the reduction in cross area of 316L stainless steel pipe all decline conspicuously because of work hardening. The fracture morphology indicates the fracture mechanism of 316L stainless steel pipe before and after the dilation is ductile fracture. The fractograph of specimen exhibits typical ductile dimples and a portion of them appear lacerate, the serpentine sliding phenomenon intersperses on it. The ductile dimples of test sample change smaller and shallower after expandable deformation, most of the serpentine sliding phenomenons vanish.
QIAN Xin, ZHI Jian-hai, ZHANG Yong-gang, YANG Jian-xing. Effect of Surface Chemical Structure of Carbon Fibers on Properties of Carbon Fiber/Epoxy Resin Composites[J]. Journal of Materials Engineering, 2014, 0(6): 84-88.
Carbon fibers with different surface chemical structure were achieved by changing the oxidative intensities in the electrochemical anodic oxidation, and then these fibers were chosen as the reinforcements of carbon fiber/epoxy resin composites. Effect of surface chemical structure on the properties of composites was researched. The results show that surface activity increases greatly after electrochemical oxidation. The relative contents of oxygen and nitrogen increase from 3.10% and 1.12% to 13.07% and 5.96% respectively. When the current density is lower than 15A/m2, the higher the values of O/C and N/C, the better the interfacial bonding between carbon fiber surface and the epoxy resin. Among the oxygen-containing functional groups, -COOH is the key factor which can determine the chemical bonding between carbon fiber surface and the resin matrix.
LIANG Tong-xiang, LIU Juan, WANG Chen. Electronic Structure of Graphene and Its Application Advances[J]. Journal of Materials Engineering, 2014, 0(6): 89-96.
Crystal-structure and electronic structure of graphene and quantum Hall effect is analyzed in this paper, the preparation of graphene is evaluated, and its application as well as the research advances are analyzed. The main problem existed in the study of graphene is explained, and the development trend of graphene is prospected.
