SHEN Rong, WANG Tian-min, BAI Hai-long, XIONG Chang-jian. Synthesize Negative Thermal Expansion Material ZrW2O8 Using Co-precipitation Method[J]. Journal of Materials Engineering, 2003, 0(3): 3-6.
The oxide material ZrW2O8 displays unusual property of isotropic negative thermal expansion in a large wide temperature range, which makes it have a number of important potential applications. Cubic ZrW2O8 was synthesized by co-precipitation route X-ray diffraction, infrared and Raman spectrum analysis shows the synthesized sample only contains cubic phase of ZrW2O8. The precursor of ZrW2O8 was studied by using thermogravimetric and differential thermal analysis(TG DTA). High temperature X-ray diffraction measurement indicates the linear negative thermal expansion coefficient of ZrW2O8 is -7×10-6 K-1 in the temperature range from 298K to 973K. The phase transition temperature from α ZrW2O8 to β ZrW2O8 is between 443K and 446K.
ZHANG Chang-qiao, ZHU Chen-fu, YU Ping, WEI Yun-he, ZHANG Xiao-ru, GAO Feng, MU Shan-liang. Molecular Dynamics Simulations of Corrosion Resistant Alloy Ni3Al in its Solidification[J]. Journal of Materials Engineering, 2003, 0(3): 7-10,34.
During the hot-dip process of the corrosion resistant alloy Ni3Al on the surface of the steel, it involves the solidification from liquid to coating. The cooling rate has great influence on the microstructure and the performance By means of molecular dynamics simulation technique, the solidification process of liquid alloy Ni3Al has been performed. The F-S N-body potentials have been adopted to describe the atomic interactions. The structural features have been revealed with the pair distribution The variation of energy with the temperature and the relationship between the energy and the microstructure has also been studied. It has been concluded that the cooling rates have important influence on the final structure of Ni3Al. The Ni3Al becomes the glass state at the relatively high cooling rate(4×1013 K·s-1), but crystallize out at the relatively low cooling rate(4×1011 K·s-1) At the same cooling rate(4×1011 K·s-1), the Ni3Al melts of which Al is more than Ni crystallize out.
WAN Ye, YAN Chuan-wei, CAO Chu-nan. Effect of Ammonium Sulfate on the Atmospheric Corrosion of Steel A3 in the Presence of Trace Sulfur Dioxide[J]. Journal of Materials Engineering, 2003, 0(3): 11-13,20.
Indoor atmospheric corrosion of steel A3 deposited with(NH4)2SO4 and in the presence of SO2 was studied by gravimetry and SEM and FTIR measurement. The results show that the samples deposited with(NH4)2SO4 before the exposure corrode much faster. The more(NH4)2SO4 the sample deposites, the much more serious the sample corrodes. The examinations of the corrosion product by SEM and FTIR show that the corrosion of A3 steel is initiated along the deposition area of(NH4)2SO4 particles. With the prolonging of the exposure time, the amount of NH4+ become less, and the phase constituents are α-FeO(OH),γ-FeO(OH),δ-FeO(OH).
WANG Hai-dou, ZHUANG Da-ming, WANG Kun-lin, LIU Jia-jun. Study on Tribological Properties of Ion Sulfuration and Thermal Sprayed FeS Solid Lubrication Layers[J]. Journal of Materials Engineering, 2003, 0(3): 14-16,43.
The methods of low temperature ion sulfuration and thermal sprayed were used to prepare the FeS solid lubrication layers respectively Their tribological properties were comparatively investigated on a ball-on-disc friction and wear tester of QP-100 model under oil lubrication SEM equipped with EDX and XRD were employed to analyze the morphologies of surface and wear scar of FeS layers, and the surfaces phase structures. The results show that the tribological properties of two layers are all superior to the plain surface, in which the friction-reduction and wear-resistance of the ion sulfuration layer are still better, and the property of anti-scuffing of the sprayed FeS is better. The difference of the tribological properties of two layers is due to their different forming mechanisms and structures. The ion sulfuration layer is prepared in the vacuum furnace and is formed through the diffusion and penetration of sulfurs into the matrix. The bond between the layer and substrate is chemical bond The layer is thin and successive. The sprayed FeS layer is prepared in atmosphere and forms through the building up of FeS grains It belongs to mechanical bond The layer was thick and contained some impurities.
LI Ping, WANG Han-gong. Study of Microstructure and Properties of Coatings of Ti-Al TwinWires Ultrasonic Arc Sprayed Alloy on Aluminum Alloy Surface[J]. Journal of Materials Engineering, 2003, 0(3): 17-20.
By means of SAS-1 arc spraying equipment, Ti-Al alloy compound coat systems were achieved on the LY12 aluminum alloy surface. The relationship between composition, phase structure and microstructure of coatings and its bond strength, micro-hardness, porosity and wear resistance, were analyzed with the optical metallurgical microscopy, SEM, XRD, EDX, EPMA. The results show that the coatings of which porosity is less than 2.8%, microhardness is above HV0.2 631, bond strength is 29MPa and dry wear abrasion volume is the same as one-seventeenth its of the aluminum alloy matrix by the SAS-1 ultrasonic arc spray systems. The metallurgical bond between coatings and substrates can be found by observation of microstructure. The coatings consist of TiAl,Ti3Al,TiN(TiO),Al,Ti. The mechanism of coatings abrasion wear may be oxidative wear and grind wear because that the hard mass phases are departed from coatings.
MA Zhuang, LÜ Guang-shu, WANG Fu-chi, WANG Quan-sheng, WANG Ying-chun. Effect of Electroless Nickel of Aluminum Substrateon the Thermal Shock Resistance of TBCs[J]. Journal of Materials Engineering, 2003, 0(3): 21-23.
The effect of electroless nickel of aluminum substrate on the thermal shock resistance of TBCs(thermal barrier coatings) was studied. The result shows that the TBCs by electroless nickel can resist 200 thermal cycles and have no visible changes However, the TBCs without electroless nickel of aluminum substrate of substrate fail through delamination after 35 thermal cycles. The main reason is that the layer of electroless nickel can efficiently relax the thermal stress at the interface between aluminum substrate and TBCs, and increases the oxidation resistance of aluminum substrate. The elements diffusion at the both sides of nickel layer can increase the bond strength of interface and induce the higher ability of resisting thermal shock.
LIU Jun-you, WU Yan-sheng, WEI Li, WANG Shi-ben, YAN Tao, LIU Wei-dong. Study on the Formation of Carbide in High ManganeseSteel and its Solution at Elevated Temperature[J]. Journal of Materials Engineering, 2003, 0(3): 24-27.
The carbides in high manganese steel can be formed during quenching at elevated temperatures and by modification treatment. The carbides look like nodular and distribute in the austenite(γ) grains under some conditions. Observed by high temperature morphology, it ia found that the carbides in as-cast can be solved into γ at elevated temperature. Meanwhile the γ crystal grows fast and its growth routes are the boundary migration and the means of the larger grains annexing the small ones. When polished layer by layer, we found that the cavities are left at the surface after the carbides solved into the γ. These results are of great valuable for developing the high manganese steel without heat-treatment and determining the heat treatment process of high manganese steel.
FU Zhi-qiang, TANG Chun-he, LIANG Tong-xiang. Impregnation Process of Fabricating SiC Coating from PCS Precursor[J]. Journal of Materials Engineering, 2003, 0(3): 28-30.
Among the impregnation parameters of fabricating SiC coating from polycarbosilane(PCS) precursor, including the concentration of PCS in solution, impregnation pressure, pressuring time, and evacuating time, the influence of the concentration of PCS in impregnation solution is most obviously while the influences of the other factors are negligible. Uniform and dense SiC coating is fabricated when the concentration of PCS does not excess 30% The thickness of coating increases as the concentration of PCS and the maximum thickness of SiC coating obtaines through one impregnation is 1～2μm.
WEI Hua-zhen, WANG Cheng-guo, WANG Hai-qing. Study on a New-type Ablative Phenolic Resin[J]. Journal of Materials Engineering, 2003, 0(3): 31-34.
Phenolic resins which had various orth/para hydroxy methyl ratios were synthesized by use of complex alkali catalysts and under various ratios of formaldehyde/phenol. The fused-ring transition mechanism of carbonization of phenolic resin could be optimized by altering the orth/para crosslink degree, the course of carbonization could go slowly and steadily, and the char yielded show a high tendency towards graphitization under high temperature, and so ablative ability could be improved. When the formaldehyde/phenol ratios were in 1.6～1.8,the phenolic resins'ablation morphological appearances were ameliorate, and their char yields and ablation rates of the composite were relatively ideal.
ZHU Jiao-qun, MEI Bing-chu, CHEN Yan-lin. The Metal Properties of the Layered TernaryCarbide Ti3SiC2 Ductile Ceramic[J]. Journal of Materials Engineering, 2003, 0(3): 35-37.
Ti3SiC2 is a layered hexagonal structure:It has a combination of both metal and ceramics properties. The excellent properties of Ti3SiC2 enable it the ideal materials for high temperature structure, electrical engineering and self-lubricating applicationsThe main synthesis methods of Ti3SiC2 include CVD, SPS, HP/HIP and SPSAdditionally, the research expectation on the compound and its using foreground are also discussed in the paper.
WANG Ya-ming, JIANG Bai-ling, LEI Ting-quan, JIA De-chang, ZHOU Yu. Research Development of Wear-resistance Coatings onTi6Al4V Alloy Surface[J]. Journal of Materials Engineering, 2003, 0(3): 38-43.
The current research evolution of wear-resistance coatings on Ti6Al4V alloy surface are reviewed, particular attention is focused on the novel microarc oxidation ceramic coatings on Ti6Al4V alloy surface Moreover, some research orientations worthy of attention in future are presented.
BI Yan-hong, JIN Zhi-hao. Study of Moisture Absorption on Carbon/Carbon Composites[J]. Journal of Materials Engineering, 2003, 0(3): 44-46.
The friction and wear behavior of C/C composites on the condition of moisture absorption has been summarized. Some topics for future reseach are suggested as well.It has been suggested that further work must be done in order to anticipate elevating densification of C/C composites and deepen recognition of wear mechanisms for moisture absorption conditions.
