XU Luo-ping, WU Xiao-chun, SHAO Guang-jie, MIN Yong-an. Effect of the Tempering Temperature on Thermal Fatigue Behavior of 4Cr5MoSiV1 and 8407 Steels[J]. Journal of Materials Engineering, 2001, 0(2): 3-7.
With the self-restricting test method, the thermal fatigue behavior of 4Cr5MoSiV1 steel and 8407 steel was investigated under the same heat treatment condition. The crack morphology and fracture surface was also analyzed. The thermal fatigue process of these steels was quantitatively investigated with a thermal fatigue damage parameter. The results indicate that thermal fatigue cracks of both steels initiate at the time between 100 to 200 cycles. The initiating cracks of 8407 steel are smaller and more equable than that in 4Cr5MoSiV1 steel Before 1600 thermal cycles, there are not obvious difference on the thermal fatigue behavior of both steels, after 1600 thermal cycles, the degree of the thermal fatigue damage of 8407 steel is lower than that of 4Cr5MoSiV1 steel. When the tempering temperature is below 640℃, the thermal fatigue behavior of 8407 steel is slightly better than that of 4Cr5MoSiV1 steel, but when the tempering temperature exceeds 640℃, the behavior of the former seems superior. The mechanism analysis of thermal fatigue reveals that the main factor affecting thermal fatigue resistance is the thermal stability and strength or hardness of steels.
LU Yong-hao, ZHANG Yong-gang, QIAO Li-jie, WANG Yan-bing, CHEN Chang-qi, CHU Wu-yang. The Twofold Effects of Grain Boundary on Fracture Behaviors in Fully Lamellar TiAl Alloys[J]. Journal of Materials Engineering, 2001, 0(2): 8-11.
Fracture behaviors of grain boundary in fully lamellar TiAl alloys were investigated by in-situ SEM technique and compression of bicrystal. The results indicate that the grain boundaries have twofold effects on fracture behaviors. On one hand, the grain boundaries are the sites of microcrack nucleation, microcracks first occur at grain boundary zone, whose propagation type depends on lamellar orientation of both side of grain boundary. On the other hand, the different grain boundaries have different hindrance effects on propagation of crack, which have corresponding effects on the fracture toughness of FL γ-TiAl alloys. The longitudinal grain boundary is beneficial for enhance for fracture toughness and the transverse grain boundary is bad for the fracture toughness. The dependant relation between fracture toughness and grain size may be elucidated by fracture behavior of grain boundary.
LIU Chu-ming, ZHANG Xin-ming, CHEN Zhi-yong, LIN Lin, CHEN Wen, LI Chen-li, ZHOU Zhuo-ping. The Effect of Middle Annealing on Cube Texture of High-purity Aluminum Foils[J]. Journal of Materials Engineering, 2001, 0(2): 12-14.
The effect of middle annealing on cube texture of High-purity aluminum foils was investigated by means of orientation distribution functions (ODFs). The results show that the deformation textures except the Cu component were rarely affected by the middle annealing temperatures But it bring about strong influence on the cube texture of aluminum foils after the final annealing. The cube texture is decreased as the middle annealing temperature is increased, while the R component is changed a little. The cube texture is the strongest in the middle annealing at 300℃/2h.
LIU Jin-lai, ZHANG Jing-hua, JIN Tao, HU Zhuang-qi. Deformation Inhomogeneity of Single Crystal Superalloy DD8 Eliminated by Low Temperature Ageing[J]. Journal of Materials Engineering, 2001, 0(2): 15-16.
Method and mechanism for eliminating deformetion inhomogeneity of Ni-base single ctystal superalloy DD8 was investigated. It is found that deformation inhomogeneity in DD8 is eliminated by additional 750℃/24h low temperature ageing,meanwhile yielding strength of the present alloy is raised. It is demonstrated by TEM observation that the inhomogeneous precipitating of fine γ′ particle under induction of applied stress is prevented by low temperature ageing, thus the homogeneity of slip deformation along is attained.
XU Xing-li, ZHOU Long-jie, MA Li-guo, DAI Jian-qing, HUANG Yong, XIE Zhi-peng. Preparation of β-Si3N4 Single Crystal Particles[J]. Journal of Materials Engineering, 2001, 0(2): 17-18,21.
The use of β-Si3N4 particles,as a seed material,is very effective for development of self-reinforcing microstructure and fracture toughness in silicon nitride ceramics. This work is to produce rod-like β-Si3N4 single crystal particles with a controlled morphology and size. β-Si3N4 Particles with a diameter of 1～2μm and length of 4～6μm are obtained by GPS sintering a mixture of 87.3wt%β-Si3N4+8.3wt%Y2O3+4.4wt%SiO2, followed by acid rinse treatments to remove residual glassy phase. The relation of morphology and size of β-Si3N4 single crystal under different sintering are studied.
TANG Jian-xin, ZENG Zhao-qiang, HU Xiao-qing, MIAO He-zhuo. TiB2-TiC Ceramics Matrix Composites Prepared by in-situ Technique[J]. Journal of Materials Engineering, 2001, 0(2): 19-21.
The principle of in-situ formation of TiB2-TiC ceramics matrix composites was analyzed in this paper. The TiB2-TiC ceramics matrix composites of high performance were fabricated by hot pressing from TiH2-B4C. The results show that the TiB2 in microstructure presents long column morphologies which improve fracture toughness of the composite.
LUO Wei, WU Zhen-tai. The Microstructure of Al2O3/TiO2-NiCrBSi Graded Thermal Barrier Coatings Produced by Flame Spraying[J]. Journal of Materials Engineering, 2001, 0(2): 22-25.
The microstructure of Al2O3/TiO2-NiCrBSi graded thermal barrier coatings produced by flame spraying processing on substrate of 1Cr18Ni9Ti has been studied by means of OPM,SEM,EDAX and XRD. The results show that Al2O3/TiO2 and Ni-base alloy is gradually transited along the direction of the coating, and the bond between Al2O3/TiO2 and Ni-base alloy is well made. There is no any chemical reaction between Al2O3/TiO2 and Ni-base alloy, no new phase is formed during spraying. A compound structure is formed in some layers when the content of one component is predominant, where the second phase is dispersed uniformly in the matrix. In other layers two phases are band-type.
DONG Shi-yun, HAN Jie-cai, DU Shan-yi. Microstructure and Friction-wear Properties of Laser Clad Cu-base Composite Coating on Al Alloy Surface[J]. Journal of Materials Engineering, 2001, 0(2): 26-29.
(Cu, Ni) solid solution based composite coating was successfully deposited on surface of Al alloy ZL104 via laser cladding process on the basis of metastable liquid separation in Cu-base melt. The composite was reinforced by in situ spherical particles. Friction and wear test of the coating was made.The results show that the (Cu, Ni) solid solution has cellular and dendritic microstructure, while the spherical particles have granular, spike or leafy substructure. The laser clad composite coatings greatly improve the wear properties of Al alloy ZL104. This contributes to high hardness of the composite and existence of the reinforced spherical particles, and also to poor mutual solubility of Cu and Fe. During the friction and wear test, ZL104 alloy mainly undergos adhesive wear and delamination while the laser clad composite under adhesive wear and abrasive wear.
YU Hui-sheng, LUO Shou-fu, WANG Yong-rui. The Technology and Microstructure of Electroless Ni-Cu-P Deposits[J]. Journal of Materials Engineering, 2001, 0(2): 30-33.
The effects of the deposition parameters such as bath composition, PH, temperature and time on the element contents and deposition rate of the electroless Ni-Cu-P deposits were studied. The electroless Ni-Cu-P deposits with various copper contents from 0 to 56.18 wt% were prepared through choosing the proper deposition parameters. The effect of copper sulfate concentration in the bathon the microstructure of the electroless Ni-Cu-P deposits was studied by using EDS and XRD. Ni-Cu-P deposits with phosphorus content more than 7.05wt% were amorphous, in the situation, the copper sulfate concentration in the bath was lower than 3g/L.
ZHU Li-qun, LIU Meng-lan, LI Xue-yuan, WANG Jian-hua. The Study of the Gradient Abradable Seal Coatings Used in Aeroengine[J]. Journal of Materials Engineering, 2001, 0(2): 34-35,21.
In order to improve the adherence of the abradable seal coatings farther,the gradient abradable seal coating was investigated. Adherence of the gradient abradable seal coating on 1Cr18Ni9Ti stainless steel substrate and cool-hot cyclic test resistance of it were examined. The results show that,compared to usual abradable seal coating,the adherence of the gradient abradable seal coating is better,and the cool-hot cyclic test resistance of the gradient abradable seal coating is greatly improved. The gradient abradable seal coating spalls from 1Cr18Ni9Ti stainless steel substrate at least after 58 cool-hot cycles,and usual abradable seal coating spalls from 1Cr18Ni9Ti stainless steel substrate after 38 cool-hot cycles.
ZHANG Hai-quan, ZHANG Yan-hua, Li, Liu-he, ZHANG Xing-an, MA Xiang-sheng. Study on Microfissuring Damage of Ni-base Superalloy under Thermal Shock of Electron-beam Welding[J]. Journal of Materials Engineering, 2001, 0(2): 36-39.
Electron beam welding (EBW) process is a complicated and violent instantaneous thermal shock process that consists of a thermal process occurred on the weldment surface and interactional mechanical process existed between the stress wave and base metal in certain depth. The reason of heat-affected zone (HAZ) microfissuring presented in superalloy EBW joints was analyzed based on thermal shock effect The influence of microfissuring damage on high temperature mechanical properties of EBW joints were also discussed. The results show that the HAZ microfissuring damage of superalloy EBW joints induces mechanical properties deterioration which is attributed to the EBW thermal shock.
HU Yong-ming, YI Xiao-su. Electrical Response of Conductive Composites under Dynamic Mechanical Loads:An Experimental Approach on Materials Structure[J]. Journal of Materials Engineering, 2001, 0(2): 40-42,46.
An innovative simultaneous measurement method has been proposed and demonstrated to record in-situ, on-line and real-time the resistivity response of conductive composites under dynamical mechanical loading. For carbon black loaded thermoplastics and carbon fiber reinforced thermoset based composites, change in resistivity has been found related to the structural change reduced by temperature and the dynamic loading. Thus, it provides not only a new way to study the structure-property relations, but it also is possible to apply the method to monitor the service performances of composite structure under real conditions.
YUAN Shen-fang, TAO Bao-qi, ZHU Xiao-rong, SHI Li-hua. Damage Self-diagnose of Composite Material Using Active Monitoring Technology and Wavelet Analysis Method[J]. Journal of Materials Engineering, 2001, 0(2): 43-46.
The main research object of this article is the health monitoring smart composite structure that can self-diagnose the damage of composite material. Active monitoring technology and wavelet analysis methods are adopted. The results can help to enlarge the usage of composite material, increase the safety, prolong the life, reduce the cost,also can provide theoretical and experimental basis to the health monitoring of other materials.
XIAO Ke. Application of Silicasol in Production of Direction Solidification Precision Casting[J]. Journal of Materials Engineering, 2001, 0(2): 47-48,7.
This paper introduced the kinds of silicasol for production of direction solidification superalloy casting, coating mixing, shell making, and showed the view on the present problem and prospect of silicasol.
