RAO Xiong, LI Xi-jiang, SI Peng-cheng, WANG Wei-hua. Recent Progress about Multicomponent Bulk Amorphous Alloys with Large Glass-Forming Ability[J]. Journal of Materials Engineering, 1999, 0(9): 3-6,12.
During the last ten years, one of the most important achievement in bulk amorphous synthesis is that certain metallic alloys can be vitrified from liquid state at low cooling rate(about 0.1～10K/s), and a number of multicomponent bulk amorphous alloys with large glass.forming ability have been gradually found. These new bulk amorphous alloys have two general features: first, they are multicomponent(at least three and very often five elements), and second, they exhibit large values of temperature interval of undercooled liquid region(Δ Tx= Tx - Tg), where Tx is the crystallization temperature of the amorphous alloys, and Tg is the glass transition temperature of the alloys. This paper aims to review recent development in bulk amorphous alloys, especially, mechanisms and improvement of large glass forming ability have been discussed.
PENG Li-ming, WEN Hong-quan, ZOU Qi-ming, MAO Xie-min. A Study on Directional Solidification of In-situ Cu-0.8Cr Alloy[J]. Journal of Materials Engineering, 1999, 0(9): 7-9.
Directionally solidified procedure of the hypo.eutectic alloy, Cu.0.8wt%Cr, under the status of non.equilibrium solidification, was studied. Results show that when the temperature gradient is 30℃/cm and the growth speed is 3μm/s and 30μm/s respectively, the microstructure of this alloy is a non.stable one of α-dendrite plus (α+β) eutectic; furthermore, the primary distance among α-dendrites increases with the rise of the growth speed of dendrites. This is in accordance with the varying rule of the primary dendritic distance within low speed period described by Hunt model, but contrary to that described by K-F model. Forming the Cr fibers depends on the surface tension of liquid Cr, the cross-wise diffusion power of Cr atoms in liquid phase, and the growth environment for Cr phase between α dendrites. So improving the diffusion of Cr, decreasing the lateral branch of α could help the formation of regular fibers of Cr.
WANG Rong-ming, TAO Chun-hu, YAN Ming-gao. Study on Microstructure of the TiB2 Reinforced NiAlFe Metal Matrix Composites[J]. Journal of Materials Engineering, 1999, 0(9): 10-12.
The microstructures and interface structures of NiAlFe-TiB2 metal-matrix.composite using the exothermal dispersion (XD) process have been investigated..The effect and micro-mechanism of iron on the compression property of the composite have also been studied. The TiB.2 particles are typically single crystal, and fairly uniformly distributed. The precipitation of the dendritic Fe(Ni,Al,Ti) phase in the composite significantly improves the room temperature ambient ductility. The interface between the reinforcement and the matrix after compression has also been studied using high-resolution transmission electron microscopy.
SUN Jian, FU Yong-feng, WU Jian-sheng, HE Yue-hui. Superplasticity of Duplex TiAl Based Alloys at Temperatures between 950～1075℃[J]. Journal of Materials Engineering, 1999, 0(9): 13-15,23.
Superplatsic deformation behaviours of duplex TiAl based alloys were investigated at temperatures ranging from 950～1075℃, and at strain rate ranging from 2×10-4～8×10-51/s. The results show that the alloy exhibits an excellent superplasticity, and a maximum elongation of 467%. The strain rate sensitivity reaches at 0.5 and above at a temperature higher than 1025℃ and a strain rate lower than 7×10-51/s. The apparent activation energy of the alloy was calculated to be 345 kJ/mol. The superplasticity of the alloy is related to dynamic recrystallization during deformation at 950℃. However, at 1000℃ and above the grain size of the alloy keep stable during deformation and the superplasticity is assumed to arise from the grain boundary sliding.
ZHANG Hui-qiang, CHEN Hong-jun, SUN Jian, YAO Yu-ming, HU Geng-xiang. Effects of Minor Additive Elements on the High-temperature Plasticity of Monel K-500 Alloy[J]. Journal of Materials Engineering, 1999, 0(9): 16-19.
Monel K-500 alloy has been modified by adding a small amount of Mg,Cr and Co elements to improve the mechanical property. The test results show that the high temperature plasticity of the experimental alloy is much higher than the commercial Monel K-500 alloy and superplasticity appears at high temperature. The index m of strain rate sensitivity and the activation energy Q of high temperature deformation were measured. It is found that Q is small in the superplastic condition,It is suggested that the superplastic deformation is a diffusion controlled process. The influence of Mg,Cr,Co additions on the fracture energy of the grain boundary has been calculated. The results show that these minor elements increase the adhesion energy of grain boundary,so the high temperature plasticity of Ni-Cu base alloy is improved.
JIANG Zhi-qiang, XIA Xiang-dong, LI Jian-guo, WANG Lai-sheng. Research on Corrosion Resistance of 1Cr18Ni9Ti Stainless Steel Welding Joint Included Rare-Earth by Electrochemistry Method[J]. Journal of Materials Engineering, 1999, 0(9): 20-23.
Rare-earth has been introduced into the welding-seam of 1Cr18Ni9Ti stainless steel by adding it to welding agent in this paper. The effects of rare-earth on the welding corrosion resistance against the caustic soda of inner mongolia were researched by high-temperature electrochemistry method. The results show tha trare-earth element can be introduced into the welding seam metal by adding proper rare.earth elements and using welding process, polarization rate of positive electrode polarzation curve of 1Cr18Ni9Ti stainless steel welding joint can be changed by adding appropriate rare-earth element, and the corrosion resistance of welding joint can be improved consequently.
LIANG Hui, JI Hui-ming, XU Ting-xian, SHEN Ji-yao. Microstructure of CdSnO3-CdWO4 Linear Thermistor Ceramics[J]. Journal of Materials Engineering, 1999, 0(9): 24-27.
In this paper, the microstructures of the CdSnO3-CdWO4 linear thermistor ceramic materials, included the composition of the phases, the parameters of the crystal lattice, the shape and size of the crystal grains and so on, are been studied with the techniques of X-ray diffraction, DTA, SEM and XRD. Meanwhile, the solid phase reactions in the process of the ceramics making are discussed.
HUANG Da-qing, WANG Zhi-yong, LIU Jun-neng. Effects of Coupling Agents on Mechanical Properties of Radar Absorbing Coatings and Its Mechanism[J]. Journal of Materials Engineering, 1999, 0(9): 28-31.
Mechanical properties of room-temperature cured radar absorbing coatings(RAC), such as tensile strength,impact strength and flexibility, are obviously improved with adding coupling agents. By way of SEM and SAM,the effect mechanism of coupling agents on mechanical properties of RAC is discussed.
GONG Yun-lan, WANG Wei, GAO Jun-li, CHENG Jie, GUO He-tong. Study on Property of Infrared Wave-absorbing of Porous Alumina Film[J]. Journal of Materials Engineering, 1999, 0(9): 32-33,36.
The porous alumina film prepared by anodization of aluminum in chromic acid under constant voltage and direct current can absorb infared wave. It was found that for the reflection spectra of porous alumina films there emerges a tendency of collapse in 1250～417 cm-1. with increasing porosity.
LIN Zheng, ZHANG Shao-wei, WU Xue-ren, YAN Ming-gao. An Investigation on Prediction of Oxidation Characteristic of Low Thermal Expansion Superalloys[J]. Journal of Materials Engineering, 1999, 0(9): 34-36.
This paper has put forward the conception about the coefficient of effect of alloy element on oxidation by oxidation increased.weight curves of six low thermal expansion superalloys with different composition. The oxidation increased-weight of experiment alloys can be predicted by the coefficients, and it coincides with the experiment result perfectly. The prediction of oxidation increased weight for low thermal expansion superalloys can be made by the coefficients of effect of alloy elements and the method in this study. It can decrease the expenditure and time of studying low thermal expansion superalloys oxidation characteristic and establish the foundation for the development of the low thermal expansion superalloys.
ZOU Bin, ZHAO Yi. Determination of Trace Sn in Quality Ti6Al4V Alloy by GFAAS[J]. Journal of Materials Engineering, 1999, 0(9): 37-39.
The method of determination of trace Sn in Ti6Al4V alloy by GFAAS has been proposed. The disturbance of basic elements in quality Ti6Al4V has been studied and the optimum conditions for determining trace Sn have been selected. The relative standard deviation is less than 3% and the recovery is 95%～102% (content of Sn is 0.005%～0.020%).. The proposed method is simple, convenient, rapid and accurate.
MO Wei-hong. Study on High Pressure Gas Quenching Behavior of H3636 Vacuum Furnace[J]. Journal of Materials Engineering, 1999, 0(9): 40-42,39.
Cooling curve of H3636 vacuum furnace was tested, the relationship between pressure and cooling ability was also studied, and the results will be the basis for further application of H3636.
SUN Xing-nan, TAN Ping, CUI Yong-fu. Influence Factors of Density for Cu-C Material[J]. Journal of Materials Engineering, 1999, 0(9): 43-45.
The influence factors of density for Cu-C material were investigated in this paper.The results show that the effect of partical size and shape on the density can not be ignored, the density would be improved if the shape of graphite is scale-like.The effect of re-pressing on the last density is significant, otherwise the sintering temperature and the first pressing strength is not dominant factor.The properties of high density compact are more perfect than those of low density compact.
XIE Ming-li, ZHANG Yi, XI Nian-sheng. An Analysis on Fatigue Fracture of Weld at Back Supporting Rod of Main Reductor of An Aircraft[J]. Journal of Materials Engineering, 1999, 0(9): 46-48.
The fatigue fracture reason of the weld seam at the back supporting rod of the main reductor of an aircraft has been analyzed by fractography and metallographic test. The result shows that fatigue fracture of the weld is due to wrong technical control of artificial weld, comparatively severe overheat and coarse microstructure were caused at the local weld, which degrades the fatigue strength of the local weld.
