2018 Vol.38(4)

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2018, 38(4): 0-0.
[Abstract](975) [FullText HTML] (370) [PDF 971KB](28)
A Review on Mg-RE Alloys with High Product of Strength and Elongation
Yangxin LI, Xiaoqin ZENG
2018, 38(4): 1-9. doi: 10.11868/j.issn.1005-5053.2018.001012
[Abstract](429) [FullText HTML] (179) [PDF 781KB](19)
The combination of magnesium and rare-earth (RE) elements can produce the lightest constructional metals, i.e. Mg-RE alloys. These Mg-RE based alloys have been used in the fields of aerospace, electronics, communications, and automobiles, etc. However, most of the Mg alloys have been suffered from the " strength-ductility trade-off” phenomenon, which limits their applications. With the present of long period stacking ordered (LPSO) phases, the Mg-RE-X alloys usually exhibit high strength, high ductility and high creep resistance, and have drawn increasing interest due to their promising mechanical properties in the past two decades. This paper reviews the development of Mg-RE based alloys, proposes a concept of high " product of strength and elongation” Mg alloys, and three main issues to be solved in future, which are (1) formation and deformation mechanisms of different structural units within a single-crystal Mg grain; (2) strengthening and toughening mechanisms in polycrystal Mg alloys; (3) manipulation of different structural units to produce Mg alloys with high product of strength and elongation.
Research Progress of As-cast Magnesium Alloys with High Plasticity
Bin JIANG, Wenjun LIU, Hanwu DONG, Renju CHENG, Na ZHANG, Fusheng PAN
2018, 38(4): 10-25. doi: 10.11868/j.issn.1005-5053.2018.001011
[Abstract](477) [FullText HTML] (128) [PDF 635KB](13)
It is necessary for cast alloys possessing sufficient plasticity to be subjected to deforming progresses for the improvement of mechanical properties. Developing as-cast magnesium alloys with appreciated plasticity is therefore important to the variety of wrought magnesium alloys and the enlargement of their applications. In this paper, the research progresses of Mg-Al, Mg-Li, Mg-Zn and Mg-RE (rare earth) series magnesium alloys are enclosed, as well as the effects of casting processes. The plasticity enhancement of as-cast magnesium alloys was mainly attributed to the combination of the grain refinement and the second phases introduced by alloying elements, and microalloying with several alloying elements was more favorited. Heat treatment, rapid cooling casting and external electromagnetic field were also beneficial to mechanical properties and worth to be promoted in industrial engineering.
Current Study and Novel Ideas on Magnesium Matrix Composites
Yang HE, Qiuhong YUAN, Lan LUO, Yuhai JING, Yong LIU
2018, 38(4): 26-36. doi: 10.11868/j.issn.1005-5053.2018.001013
[Abstract](856) [FullText HTML] (267) [PDF 648KB](23)
Magnesium alloy is the lightest metal structural material, but its low strength, low plasticity and poor corrosion resistance severely limit its wide application as a light metal material in the engineering field. Magnesium matrix composites are considered to be one of the most advantageous ways to improve the mechanical properties of magnesium alloys and realize their industrial applications because of their high specific strength, specific stiffness, specific modulus and light weight. The article focuses on the current study of magnesium matrix composites enhanced by carbon nanotubes, graphene and SiC. The bottleneck of magnesium matrix composites is analyzed from the aspects of reinforcement dispersion, interface bonding and structural stability. The new ideas for the design of magnesium matrix composites are introduced from the aspects of surface modification of reinforcements, design of matrix alloy, and preparation process of the composite material. Also the development trend and research direction of future magnesium matrix composites are proposed.
Research Progress of Metal-Intermetallic Laminated Composites
Fantao KONG, Wei SUN, Fei YANG, Xiaopeng WANG, Yuyong CHEN
2018, 38(4): 37-46. doi: 10.11868/j.issn.1005-5053.2017.000204
[Abstract](619) [FullText HTML] (335) [PDF 2452KB](39)
Metal-intermetallic laminated composites not only retain the high temperature strength of intermetallics, but also possess the high toughness and ductility of metal at room temperature which are gradually becoming the research priorities of domestic and overseas researchers. In this article, authors introduced Ti-Al, Ni-Al, Fe-Al, Nb-Al and other common metal-intermetallic laminated composites and emphasized on the advantages and disadvantages of synthesis methods, such as hot-pressing, explosive welding, spark plasma sintering and so on. The toughening mechanisms inside and outside of metal-intermetallic laminated composites were summarized. Finally, the deficiencies about the research of metal-intermetallic laminated composites at present were analyzed. The research must focus on the Ti-Al laminated composite. Improving the ductility and toughness at room temperature, researching the toughening mechanism and optimizing the fabrication process are the key issues to the engineering application of metal-intermetallic laminated composites.
Research Progress on Deployable Structures of Shape Memory Polymer Composites
Tianning REN, Guangming ZHU, Jing NIE
2018, 38(4): 47-55. doi: 10.11868/j.issn.1005-5053.2017.000159
[Abstract](788) [FullText HTML] (353) [PDF 912KB](32)
As a new kind of smart material, shape memory polymers (SMPs) show great promise in aerospace. Intelligent material structure with low cost, smooth process, low vibration, high strength and excellent electrical conductivity, and its composite with a certain reinforced phase can be designed according to the mechanism, composition and structure of the polymeric material. In this paper, three kinds of matrix for shape memory polymer composites and the method of preparing shape memory structures for each matrix are introduced. From macro structures, the three kinds of SMPs are discussed in separate deployable structures. The shape-memory mechanism, recovery rate, fixed rate, and response speed are presented in detail. Also, some applications of shape memory polymer composites in space deployable structures are introduced.
Review Thermomechanical Processing and Microstructure of High Strength-toughness Titanium Alloy
Huan WANG, Yongqing ZHAO, Shewei XIN, Wei ZHOU, Qian LI, Siyuan ZHANG
2018, 38(4): 56-63. doi: 10.11868/j.issn.1005-5053.2017.000193
[Abstract](317) [FullText HTML] (136) [PDF 981KB](17)
High strength-toughness titanium alloy has gradually attracted considerable attention as important engineering material in aerospace industry. Forging is a main thermomechanical processing method in high strength titanium alloy, With the major purposes of refining grain and optimizing mechanical properties through microstructure control during the different stages of thermomechanical process. The grain refinement occurs mainly in the process of ingot breakdown and substituting forging, which affects the static and dynamic recrystallization of the alloy by controlling the forging temperature and deformation. The microstructure control is mainly occurred in the finished forging stage by controlling the forging temperature and phase transformation of the alloy. This article describes the research development of the thermomechanical process for high strength-toughness titanium alloys, summaries the effect on the microstructure of thermalmechaical process from the two aspects of refining the grain and controlling the structure from.
Effect of Mo content on Microstructure and Mechanical Properties of IN718 Alloy
Dawei HAN, Wenru SUN, Lianxu YU, Fang LIU, Bin ZHANG, Zhuangqi HU
2018, 38(4): 64-74. doi: 10.11868/j.issn.1005-5053.2018.000025
[Abstract](652) [FullText HTML] (370) [PDF 1652KB](38)
The effect of Mo content on microstructure and mechanical properties of IN718 alloy after standard heat treatment was investigated by means of optical microscopy(OM), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and energy dispersive spectrometer(EDS). The results show that Mo significantly affects the intergranular precipitation. The amount of δ phase is decreased by the increase of Mo addition up to 4.00%. However, δ phase is inhibited thoroughly but Laves phase begins to precipitate at grain boundaries when Mo addition is higher than 5.50%, and the precipitation of Laves phase is increased by the increase of Mo content. Both the disk-shaped γ″ phase and spherical γ′ phase are precipitated in γ matrix grain in all of the alloys with the Mo additions ranging from 2.8% up to 7.5%, and there are no other second precipitates. Mo has no obvious effect on the number of the precipitation of γ″ phase and γ′ phase, but their sizes are decreased with the increase of Mo addition. Mo slightly reduces the tensile strength of IN718 alloy at room temperature and yield strength at 680 ℃. At room temperature, Mo addition lower than 5.5% has no evident effect on the tensile ductility, while the ductility is remarkably decreased when Mo addition is 7.50%. At 680 ℃, the ductility is enhanced gradually as Mo addition increases. Mo obviously improves the stress rupture life of IN718 alloy at 680 ℃ and 725 MPa. The life of the alloy with 7.50% Mo is about 1.5 times as long as that of the alloy with 2.8% Mo. Mo has no obvious effect on the tress rupture ductility.
Effect of Pressure on Microstructure and Mechanical Properties of Squeeze Casting Mg-6Zn-1Al-0.5Mn-0.5Ca Alloy
Rong WANG, Qichi LE, Engang WANG, Jianzhong CUI, Zheng REN, Xiangyu CHENG, Xiao ZHANG, Xiurong ZHU, Min CHEN
2018, 38(4): 75-81. doi: 10.11868/j.issn.1005-5053.2017.000156
[Abstract](319) [FullText HTML] (116) [PDF 2237KB](11)
The effect of pressure of squeeze casting on the microstructure and mechanical properties of Mg-6Zn-1Al-0.5Mn-0.5Ca alloy has been systematically studied using XRD. SEX. TEM and tensile test. The results show that the microstructure of the as-cast alloy consists of α-Mg matrix with τ(Mg32(Al, Zn)49) and some Al8Mn5 second phase particles. The imposed pressure dose not change the composition of alloy phase precipitation. With the increase of squeeze casting pressure, the second phase particles of the as-cast ZAMX6100 alloy becomes more and fine, and more uniformly distributed. Simultaneously, ZAMX6100 alloy solidified under pressure improves the uniform distribution of micro-elements Mn, Ca, which decreases the extent of interdendritic segregation. When pressure is increased from 0 MPa to 100 MPa, the tensile strength, yield strength, elongation and hardness of ZAMX6100 alloy are all improved by 27%, 14%, 31% and 9% respectively. The fine ZAMX6100 alloy microstructure is mainly caused by the atom spread activation energy decreasement under pressure during the solidification, which decreases the crystal growth velocity, and at the same time the high pressure squeeze casting causes an entire contact of magnesium alloy with the mold inside, which causes the increase of cooling rate and refinement of microstructure.
Wear and Corrosion Properties of Cold Sprayed 420 Stainless Steel/WC-17Co Coating on Magnesium Alloy
Jie CHEN, Hui SONG, Yu DAI, Bing MA, Ziyun ZHENG, Li JIA
2018, 38(4): 82-86. doi: 10.11868/j.issn.1005-5053.2017.000161
[Abstract](425) [FullText HTML] (121) [PDF 1636KB](14)
420/WC-17Co coating was deposited on AZ80 magnesium alloy substrate by cold spraying technology. SEM was used to characterize the original powder morphology and coating microstructure. The microhardness and bonding strength of as-sprayed coating were tested by microhardness tester and universal material testing machine. Moreover, friction and wear property of the coating was also investigated by a ball-on-disk tribometer. Corrosion behaviours of coatings and magnesium alloy were characterized by electrochemical measurements. The results show that high quality 420/WC-17Co coating can be deposited on AZ80 magnesium alloy by cold spraying technology. The microhardness of cold sprayed 420/WC-17Co coating is (615 ± 62) HV, bonding strength is (57 ± 11) MPa and wear rate is only 3.3 × 10–6 mm3·N·m. The wear resistance of cold sprayed 420/WC-17Co coating is improved by two orders of magnitude, and the corrosion current density is reduced by one order of magnitude than magnesium alloy substrate. In conclusion, the present research demonstrates that cold sprayed 420/WC-17Co coating can significantly improve the surface performance of magnesium alloy substrate without evident heating output.
Effect of SPS Sintering Temperature on Properties of ZrB2-SiC Ceramic
Qi LI, Fengwei GUO, Lamei CAO, Xiaosu YI
2018, 38(4): 87-92. doi: 10.11868/j.issn.1005-5053.2017.000082
[Abstract](293) [FullText HTML] (148) [PDF 807KB](15)
Two ZrB2-20% (volume fraction) SiC(ZS) ceramics were sintered successfully by spark plasma sintering (SPS) process at 1700 ℃ and 1900 ℃ respectively. The SEM, EDS, hardness, fracture toughness, bending strength, mass gain and cross section of oxidized ceramics were analyzed to investigate the effect of sintering temperature on microstructure, mechanical properties and oxidation resistance of ZS ceramic. The results show that the grain size and relative density of ZS ceramic are increased with the increase of sintering temperature. When the sintering temperature is raised from 1700 ℃ to 1900 ℃, the density increases from 98% to 99.8% and the hardness increases from 12.6 GPa to 14.7 GPa. With the increase of sintering temperature form 1700 ℃to 1900 ℃, the bending strength at 1600 ℃ increases from 101 MPa to 286 MPa, and the bending strength at 1800 ℃ increases from 138 MPa to 302 MPa. The oxidation behaviours of the two ceramics at 1500 ℃ in air are also investigated. The oxidation depth of ZS ceramic sintered at 1900 ℃ is smaller, and the infiltration of O into the substrate is less, which indicates that the oxidation resistance of ZS ceramic sintered at 1900 ℃ is improved.
Effect of Ultrasonic Vibration on Microstructure and Mechanical Properties of Nano-SiCp/Al-5Cu Composites
Jianyu LI, Shulin LYU, Shusen WU, Kang LU, Qi GAO
2018, 38(4): 93-100. doi: 10.11868/j.issn.1005-5053.2017.000213
[Abstract](473) [FullText HTML] (142) [PDF 2232KB](13)
The ultrasonic vibration (UV) treatment has been successfully applied to improve the particles distribution of nano-SiCp reinforced Al-5Cu composites fabricated by combined processes of dry high energy ball milling and squeeze casting. Large particles aggregates are eliminated by effects of the cavitation and the acoustic streaming of UV for 1 min. All the particles aggregates are eliminated and the particles are uniformly distributed in the melt after treated by UV for 5 min. The ultimate tensile strength, yield strength and elongation of the 1%(mass fraction) nano-sized SiCp/Al-5Cu composites treated by UV for 5 min are 270 MPa, 173 MPa and 13.3%, which are increased by 7.6%, 6.8% and 29% compared with Al-5Cu matrix alloy, respectively, and are increased by 27.4%, 9.5% and 303% compared with the untreated composites, respectively. The improvements of mechanical properties after UV are attributed to the uniform distribution of reinforcement and grain refinement of aluminum alloy matrix.
Effect of Rare Earth Y on Microstructure and Properties of Sn-58Bi Solder Alloy
Liukui GONG, Jinfa LIAO, Jihui YUAN, Guihe LI, Huiming CHEN
2018, 38(4): 101-108. doi: 10.11868/j.issn.1005-5053.2018.000007
[Abstract](1098) [FullText HTML] (438) [PDF 3220KB](35)
Sn-58Bi-xY alloys with different Y contents (x = 0.0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% (mass fraction, the same below )) were fabricated in a vacuum furnace in nitrogen atmosphere. Microstructure, phase composition, melting characteristic, wettability and hardness of the alloys were investigated, and the influence of the rare earth Y on the formation of intermetallic compound among Sn-58Bi/Cu were analyzed, and the shear strength were test. The results show that the Sn-Bi microstructure is refined, and the microstructure of Sn-58Bi-xY is rich in Sn phase, Bi phase and eutectic microstructure of layered structure. The rare earth Y is distributed in rich Bi phase evenly. The melting points and melting ranges are less affected with the Y addition. The wettability of Sn-58Bi alloys reduces when the Y contents increase, but the hardness of Sn-58Bi alloys increases and reaches the maximum value 24.18HV when the content of Y is 0.4%. Rare earth Y can improve the shear strength of Sn-58Bi-xY/Cu solder joints, and the shear strength of the joints reach the maximum value 53.55 MPa when the content of Y is 0.2%. Y can promote the reaction of Sn-58Bi solder with Cu during welding and forming Cu6Sn5 intermetallic compound.
Direct Lightning Test Research on Composite Laminate with Copper Wire Mesh
Yao XIAO, Shulin LI, Junjie YIN, Xueling YAO, Xianhang ZHANG
2018, 38(4): 109-114. doi: 10.11868/j.issn.1005-5053.2017.000194
[Abstract](218) [FullText HTML] (121) [PDF 765KB](8)
In order to study the lightning protection effect of copper wire mesh on composite materials, two different lightning current waveforms were used to simulate the lightning current impact test on composite specimens with and without copper wire mesh in different sizes. Through visual damage observation, optical microscope amplification and ultrasonic damage scanning, the lightning damage degree and characteristics of composite materials were compared and analyzed. The experimental results show that when the lightning current waveform is 1 and peak currents are 50 kA and 80 kA, the lightning strike damage area and depth of the Type1 specimen without copper wire mesh are 1785 mm2, 0.63 mm and 3041 mm2, 0.96 mm respectively, while the test specimens with copper wire mesh in the same type are basically scatheless. When the lightning current waveform is 2 and the peak current is 40 KA, the lightning strike damage area and depth of the Type2 specimen without copper wire mesh are 2156.75 mm2, 0.36 mm, while the damage area of the test specimen with copper wire mesh in the same type is less than 100 mm2, and the inner layer has not been damaged. There exists a threshold value for the maximum lightning current strength of the 0.25 mm copper wire mesh, which can be expressed by the action integral. The lightning protection effect is independent of the specimen size, and is only related to the action integral, the corresponding threshold value of which is about 85218 A2·s.
Defect Control and Curing Process Simulation for T700/603 Composites
Guiyang LI, Guanghui ZHAO, Zhichang HAN, Hongjun GUO, Yanxia LI, Xiaonan ZHANG
2018, 38(4): 115-122. doi: 10.11868/j.issn.1005-5053.2017.000002
[Abstract](415) [FullText HTML] (198) [PDF 1064KB](17)
The autoclave curing process of advanced grid-stiffened MT300/603 composite has been simulated based on heat-conducting/curing-reaction and resin-flowing/fiber-compaction. The fiber volume fractions and internal defects were evaluated and investigated in term of the curing temperature, brazing time, pressure applying point and molding pressure, which were used to set up the defect control and process improvement. Furthermore, the ϕ1 m grid stiffened cylinder was prepared to verify the availability for this process optimization method. The results show that increasing pressure and enhancing pre-bulking can significantly improve the internal quality and load-carrying ability of ϕ1 m specimen.
Experimental Investigation of High-temperature Crack Propagation Behaviors for Ti-6Al-4V/ELI at 250
Zhiyang LYU, Junjiang XIONG, Yanguang ZHAO, Shaojun MA
2018, 38(4): 123-129. doi: 10.11868/j.issn.1005-5053.2016.000155
[Abstract](307) [FullText HTML] (104) [PDF 1127KB](10)
Fatigue crack propagation behaviors at high temperature are important preconditions for damage tolerance design in aircraft and engine structures.Therefore, fatigue tests were carried out on titanium alloy Ti-6Al-4V/ELI subjected to constant amplitude loading at two temperatures of 25 ℃ and 250 ℃ and three stress radios of 0.06, 0.5, -1 to determine fatigue crack propagation behaviors. Fatigue crack propagation da/dNK curves and da/dNK-R surfaces were obtained from experimental data by secant method. Those behaviors at different temperatures were compared and analyzed, and the interaction mechanism between high-temperature and fatigue load was deduced from fractographical study by SEM analysis.The results show that the larger the stress ratio R, the faster the rate of crack propagation of Ti-6Al-4V/ELI under the same temperature and stress intensity factors rangeΔK. Oxidation products and large numbers of secondary cracks are found on the fatigue fracture surfaces at high temperature and the destruction mode of crack propagation is gradually changed form cleavage to quasi-cleavage. Acceleration effect of oxidation and deceleration effect of secondary cracks combine affecting the crack propagation rate; when R is 0.5 or 0.06, those two seem equal and the effect of temperature is not obvious, while R is -1, more and deeper secondary cracks caused by fully interaction of high temperature and fatigue load make crack propagation rate at high temperature lower than that at room temperature.
Delamination Behavior of an Advanced Al-Li Alloy Laminate during Fatigue Crack Growth
Xiao HUANG, Yi HUANG, Jianzhong LIU
2018, 38(4): 130-136. doi: 10.11868/j.issn.1005-5053.2018.000050
[Abstract](270) [FullText HTML] (109) [PDF 839KB](11)
The delamination shape and size of fiber metal laminate are the key factors to study the fatigue crack growth behavior. To study delamination behavior of an advanced Al-Li alloy laminate during fatigue crack propagation process, the relation of the delamination size between the region with nearly 0 strain on the surface of specimen and the delamination region was obtained by finite element method. The strain data from digital image correlation (DIC) was correlated with the true delamination data. The method was proved by experimental data of delamination under different lay-up structures, saw-cut lengths and crack lengths; and the real-time monitoring of delamination behavior of the advanced Al-Li alloy laminate during fatigue crack growth was realized. The results show that this method has excellent applicability, economy and data consistency.
Interfacial Fracture Toughness of Carbon Fiber Reinforced Composites
Zonghong XIE, Shujie CAI, Qi GUO, Xiang LI
2018, 38(4): 137-142. doi: 10.11868/j.issn.1005-5053.2016.000189
[Abstract](386) [FullText HTML] (157) [PDF 705KB](21)
Interfacial fracture toughnesses of composite Mode I and Mode Ⅱ were investigated by double cantilever beam (DCB) and end notch bending (ENF) test. Using stereo microscope to record crack tip and CCD camera position to observe the evaluation of lesion, the phenomenon of matrix cracking and layer extension were analyzed, and the characteristics of interlayer fracture were studied. The effect of curing method on fracture toughness was analyzed through contrast experiment. The results show that crack propagation process is not stable and the load fluctuates up and down with the increase of displacement and crack length in fracture toughness test of Mode I , while the crack produced in fracture toughness test of Mode Ⅱ does not extend initially and the load increases linearly with the displacement. When the load approaches the critical load Pc, the crack propagates unsteadily along the layer and the load drops sharply. Fracture toughness of Mode I material prepared by autoclave curing is 43% more than that of the material prepared by hot-bonder curing, while fracture toughness of Mode Ⅱ material prepared by autoclave curing is 19% more than that of material prepared by hot-bonder curing.

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