航空材料学报

Character of Artificial Non-metallic Inclusions in HIPed FGH96 Alloy

ZHOU Xiao-ming, WANG Wu-xiang, YANG Hong-tao, TANG Ding-zhong, YAN Ming-gao

2005, 25(4): 1-5.

[Abstract](1510) [PDF 1363KB](291)

Abstract:
The character of three kinds of artificial non-metallic inclusions in HIPed P/M FGH96 alloy was investigated. The results show that the three kinds of inclusions indicate distinct morphologies and interface structures. And the influence of the three kinds of interface structures on mechanical property of the matrix is illuminated by micro-hardness test.

Effect of Melt Mixing on the Microstructure in Al-5%Fe Alloy

ZHOU Zhen-ping, LI Rong-de, MA Jian-chao, WANG Yi

2005, 25(4): 6-9.

[Abstract](1407) [PDF 343KB](275)

Abstract:
The melt treatment by mixing high temperature melt with low temperature melt was adopted to refine the primary Al3Fe compound. The experimental results showed that melt treatment may improve the morphology and refine Al3Fe compound: the microstructure in the alloy without melt treatment was mainly composed of thick, long needle-like Al3Fe that was sparsely distributed and non-uniform. However, thick needle-like Al3Fe compound was transformed into thin needle-like and grain-like after melt treatment. Furthermore, the uniformity and density of microstructure were greatly improved. The results also suggested that there existed a better combination of high and low temperature melt. Over-high temperature led to coarse microstructure. The results of X-ray diffraction showed that the iron-rich compounds in the alloy with or without treatment were not changed, which were still α-Al and Al3Fe compound. The main reasons for refining the microstructure were raising the nucleation rate and inhibiting the growth along the preferred orientation.

Study on the Dynamic Hot Compression Behavior and Deformation Mechanism of TA15 Titanium Alloy

XU Wen-chen, SHAN De-bin, LI Chun-feng, LüYan

2005, 25(4): 10-15,19.

[Abstract](1678) [PDF 1317KB](536)

Abstract:
To study the dynamic hot deformation behavior of TA15(Ti-6Al-2Zr-1Mo-1V) alloy, the hot compression experiments adopting cylindrical specimens at constant strain rates were executed on Gleeble-1500 simulator(deformation temperatures of 5501000 and strain rates of 0.011s-1), the deformation activation energy Q was calculated and the hot deformation microstructure was observed. The results show that the flow stress decreases with deformation temperature rising and increases with strain rate growing. The flow deformation behavior could be divided into three types of working hardening(550600), dynamic recrystallization(650900) and dynamic recovery(9501000). The calculated deformation activation energy is 517kJ/mol in (α+β) phase region and 205kJ/mol in β phase region. The flow stress curves, deformation activation energy and deformation microstructure reveal that the main softening mechanism is dynamic recrystallization in (α+β) field and dynamic recovery in β field. As the strain rate declines the dynamic recrystallization proceeds more adequately in (α+β) region and the subgrain of dynamic recovery has the tendency to grow in β region.

Effect of Heat Treatment on the Microstructure of Two-step Forging for High Nb Containing TiAl Alloy

XU Li-hua, XU Xiang-jun, WANG Yan-li, LIN Jun-pin, SONG Xi-ping, LIN Zhi, CHEN Guo-liang, LI Shu-suo, SU Xi-kong, HAN Ya-fang

2005, 25(4): 16-19.

[Abstract](1470) [PDF 552KB](250)

Abstract:
Effect of heat treatment processings on the microstructure of two-step forging for high Nb containing TiAl alloy was investigated. Different heat treatment processes were employed to obtain different microstructures of Ti-45Al-9(Nb,W,B,Y) alloy. The results show that, after the heat treatment of 1310/20min+1250/2h/AC, the β phase can be efficiently eliminated and the uniform fine duplex microstructures can be gained. Followed by the heat treatment at α single phase region directly, striped FL microstructure of coarse colony and fine colony is obtained. The holding at (α+γ) phase region can result in the homogenous fine FL microstructure relatively. The FL microstructure produced by the heat treatment of HT6 is the most homogenous and finest.

Study on the Metallurgical Structure Characters of Sub-surface Layer of Ultra-high Strength Alloy Steel in High Speed Milling Condition

ZHAO Wen-xiang, LONG Zhen-hai, WANG Xi-bin, WANG Hao-chen

2005, 25(4): 20-25,29.

[Abstract](1406) [PDF 1093KB](342)

Abstract:
With the cutting speed of 157314m/min, by use of 23-1 factorial design, the high speed dry face-milling experiments were carried out on an ultra-high strength alloy steel, a type of difficult-to-cut materials used widely in ordnance industry. Beside the regularity of cutting parameter on surface roughness, the characters of metallurgical structure and microhardness distribution in work-piece’s sub-surface layer were also discussed.It was concluded that, when high speed milling of this ultra-high strength alloy steel, the cutting parameter had remarkable effects on the metallurgical structure of sub-surface layers; the effects were plastic deformation, over tempered martensite, under tempered martensite etc.; larger feed per tooth in high speed milling process could bring unremarkable influence on the metallurgical structure of sub-surface layers.

A Study of Fatigue Life of TC4 Titanium Alloy Sheet and Its High Density Beams Welded Joints

LI Xiao-yan, GONG Shui-li, CHEN Li

2005, 25(4): 26-29.

[Abstract](1395) [PDF 621KB](357)

Abstract:
Fatigue strength of TC4 titan ium alloy sheet and its laser beam and electron beam welded joints was investigated experim en- tally. The m ed ian fatigue life values of the welded joints, under various stress levels, were evaluated by statistic approach. The effect of weld ing cond ition on the fatigue life of the joints was analyzed. Itwas found that the fatigue life of the h igh density beam welded joint, under h igher stress levels, was shorter than that of the base m etal, however, the fatigue life of the h igh density beam welded joints was longer than that of the base m etal under lower stress levels.

High-temperature Thermal Stress and Strain of Modified Polyacrylonitrile Oxidized Fiber During Carbonization Process

LIU Yang, LIU Jie

2005, 25(4): 30-34.

[Abstract](1541) [PDF 1045KB](352)

Abstract:
Polyacrylonitrile (PAN) precursors were post spinning modified by the use of KMnO4, which was aimed to result in certain improvements in the quality of carbon fibers. Comparative studies on the thermal stress and strain of modified and unmodified stabilization fiber during carbonization process were performed. Some conventional characterization methods, such as density, mechanical properties, orientation index, etc and SEM, WAXD and EA were employed to characterize the effects of modification on the structure and properties of all fibers. The result indicated that the thermal stress and strain of modified fiber was compartmentalized into 4 temperature regions by the points of 370, 500 and 900℃. It’s stress increased rapidly under 370℃, decreased swiftly in 370~500℃, raised remarkably in 500~900℃, kept almost invariable above 900℃. At the same time, modified fiber elongated easily in heavy pre-load and shrunk easily in light pre-load. The difference between thermal strain of modified fiber and that of unmodified fiber became unremarkable along with the decrescence of pre-load. The trend of speed of the two fibers’ strain was close above 500℃. Because the thermal stress and strain of modified fiber were well related to its structure, chemical component and thermal reaction ability, and the variation of stress vs. temperature was remarkable, it was a good choice to use the stress to control the changes of structure of fibers during continuous carbonization process. The tensile strength of carbon fiber which made by modified fiber was 20% greater than that of unmodified.

Numerical Simulation and Experimental Research on Superplasticity of Ceramic Matrix Laminated Composite

WANG Guo-feng, ZHANG Kai-feng, HAN Wen-boWANG Zhen-jie, WANG Chang-wen

2005, 25(4): 35-39.

[Abstract](1430) [PDF 788KB](243)

Abstract:
In order to investigate the superplasticity of ceramic matrix laminated composite, the superplastic deep-drawing process was simulated by FEM. The results shown that the strain and stress conditions of laminated composite, made by ceramic with different superplastic formability, were better than that of monolithic ceramic. Consequently, the material might had superior superplasticity. Tape casting and hot-press sintering were used to fabricate Al2O3/3Y-TZP laminated composite. As-received material was deep-drawing at high temperature to research its superplasticity. The results shown that when suitable strain rate and forming temperature were used, the as-received material had superior superplasticity. This testified the conclusion of FEM simulation.

Experimental Studies of CAI of Woven-fiber Laminates Composite on Hygrothermal Environment

PAN Wen-ge, JIAO Gui-qiong, XIONG Wei, GUAN Xin, YANG Jie, ZHAO Mou-zhou

2005, 25(4): 40-44.

[Abstract](1496) [PDF 497KB](274)

Abstract:
Compress after impact(CAI) of glass-fiber woven reinforcement epoxy laminates was investigated experimentally at room temperature and hygrothermal environment. The results of experimentation indicated that balanced moisture content of this composites was up to 2.2%, and property degradation which depended on specimen thickness took place during moisture absorption. After composites obtained balanced moisture content, average impacted energy decreased by 19.2%, and average ultimate failure stress of CAI decreased by 54.3% at 70 with 85% relative humidity.

Study on the Reaction of the Brominated Epoxy and Cyanate Co-curing System Promoted by Imidazole and Its Cured Compounds’ Anti-oxidation and Flame Retarded Properties

WANG Ge, LI Gong-yi, LI Xiao-dong, TANG Yun, CHEN Guo-min

2005, 25(4): 45-49.

[Abstract](1405) [PDF 221KB](497)

Abstract:
To get better anti-oxidation and flame retardant properties, epoxy E51 were modified by cyanate ester BCE and brominated epoxy EX48. Here the new co-curing system was studied. A kind of imidazole 2E4MZ was introduced to the co-curing system. The co-curing behavior and reaction mechanism of E51/BCE/EX48 promoted by 2E4MZ were studied by FT-IR and DTA. Results showed 2E4MZ effectively promoted the co-curing reaction: the reaction was markedly speeded; at the same time the cured compounds’ structure was improved with more co-curing structures and less self-curing structures. Thermal analysis, flash point and oxygen index results indicated cured compounds promoted by 2E4MZ had better anti-oxidation and flame retardant properties than co-cured compounds without 2E4MZ.

Monitoring for Residual Strain of Resin Cure During the Process of RTM Composites

QIN Wei, WU Xiao-hong, CAO Mao-sheng

2005, 25(4): 50-52.

[Abstract](1389) [PDF 147KB](348)

Abstract:
The monitoring system of fiber Bragg grating for the RTM curing process was established. The real time monitoring for residual strain induced by resin cure during the RTM process was realized by measuring the relationship among wave deflection,temperature and curing time. The result shows that the relationship between the residual strain and the temperature change is approximately linear during the process of cooling, which supplies experimental support for the residual stress analysis of composite plate.

Effects of Concentration of Sodium Hydrate on Anodizing for Magnesium Alloys

QIAN Jian-gang, LI Di, GUO Bao-lan

2005, 25(4): 53-58.

[Abstract](1477) [PDF 976KB](454)

Abstract:
The anodizing of AZ91D Mg alloys in the solution of different concentration of NaOH was investigated by ways of voltage-time curve, immersion corrosion experiment, polarization curve, XRD, SEM, EDS and XPS respectively. The results show that anodizing process can be divided into three stages:formation of dense film before sparking, formed porous film accompanied with a bit of small spark, and porous film stable growth along with bigger spark. With increasing concentration of NaOH in the solution of the anodizing, the time and voltage of spark formation decrease and particle, porosity, thickness of anodic oxide film become smaller. The anodic oxide film contains MgO and a small quantity of Mg3B2O6. The concentration of NaOH has great effects on corrosion resistance of anodic oxide film. The anodic oxide film has best corrosion resistance when the concentration of NaOH in the solution of the anodizing is 40g/L.

Study of Continuous Temperature Changing on the High Temperature Oxidation Behavior of Laser Cladding Metal-ceramic Composite Coating

ZHANG Wei-ping, LIU Shuo

2005, 25(4): 59-62.

[Abstract](1524) [PDF 702KB](291)

Abstract:
In-situ synthesized Ni-base metal-ceramic composite coatings with different proportion of composition were fabricated on 45 steel surface by laser cladding. The main ceramic phase was TiB2 in the coating and its surface quality was fairly good. Analysis of high temperature oxidation kinetics of the coatings in continuous changing temperature showed that the stable oxidation remaining time and the violent oxidation speed was a certain different from each other as the coating composition changing. In addition, the surface morphology quality, size and distribution of the oxide production were different from each other as a result of the changing of the coating composition. In general, the high temperature oxidation resistance of the material surface improved greatly through laser cladding surface modification.

2005 Vol. 25, No. 4