BAO Ru-qiang, HUANG Xu, HUANG Li-jun, CAO Chun-xiao. Investigation on Hot Deformation Behavior of Ti-10V-2Fe-3Al Alloy[J]. Journal of Materials Engineering, 2003, 0(12): 3-6,10.
The hot deformation behavior of two different microstructures of Ti-10V-2Fe-3Al alloy at temperature in the range of 650～900℃ and with strain rates from 0.001s-1 to 10s-1 had been studied using Gleeble-3500 thermal simulation testing machine. The results show that the initial microstructure greatly affects hot deformation behavior of this alloy;solution treated alloy has higher flow stress than untreated alloy under the same condition when deformation temperature is below β transus point;but flow stress has no obvious difference when deformation temperature is above β transus point;stress exponent(n) has relationship with microstructure and strain rate;stress exponent is approximately divided into two regimes by strain rate 0.1s-1. Whereas the apparent activation energy(Q) is affected by microstructure, temperature and strain rate. Within the β phase dynamic recovery takes place but within the α phase dynamic recrystallization may take place besides dynamic recovery when the alloy is deformed at temperature in the range of 650～800℃ and with strain rates from 0.001s-1 to 0.1 s-1. However, the only restoration mechanism is dynamic recovery when the alloy is deformed above β transus point.
HE Xiao-dong, ZHANG Jian-xun, GONG Shui-li, LI Ji-hong. Residual Stress Measurements with the Hole-drilling Technique in the Joints by the Laser and TIG Welding for a Thin Plate of Titanium Alloy[J]. Journal of Materials Engineering, 2003, 0(12): 7-10.
A hole-drilling technique was used to determine the residual stress in laser beam welding (LBW) and TIG welding joints of titanium alloy thin plate. The effects of different welding technologies, heat input and post-weld heat treatment on residual stress distributions were analyzed. The results show that the distribution of laser welding residual stress is similar to that of traditional fusion welding processes, but the zones of distribution are much narrower. Compared to that of TIG welding in HAZ, the values of laser welding residual stress are lower about 100MPa. For the different heat input of LBW, the heat input is higher, the weld is wider and the residual stress in HAZ is bigger. Post-weld vacuum heat treatment would relieve residual stress about 90%.
DING Xiao-fei, SHEN Yong, WANG Fu-gang, TAN Yi. Effects of W,Nb on Thermal Stability of the γ-TiAl-based Cast Alloys[J]. Journal of Materials Engineering, 2003, 0(12): 11-13.
Thermal stability of the as-cast lamellar structure of the TiAl-5Nb,TiAl-14.3Nb, TiAl-8Nb-1W, TiAl-12.3Nb-2W(atom fraction,%) at 1000℃ was studied by OM,SEM and XRD.The results show that the thermal stability of the TiAl-12.3Nb-2W alloy was best,but the precise mechanism for this improvement stability needs to be clarified.
HU Zheng-fei, YANG Zhen-guo. Embrittlement of X20CrMoV12.1 Heat-resistant Alloy Steel for Long Term Exposure at Elevated Temperature[J]. Journal of Materials Engineering, 2003, 0(12): 14-17,22.
12%Cr heat-resistant alloy steel of X20CrMoV12.1 is used as main steam pipe and other critical components in power plants. The properties of the main steam pipe degraded greatly after service at elevated temperature for 23 years and had a tendency to embrittle in room temperature. Further investigation shows this phenomenon is typical reverse temper embrittlement (RTE) effect. The microstructure studies indicate that the segregation of harmful element P and the coarsened carbides at prior austenite boundaries result in the degradation of properties and embrittlement.
GUO Jian, WANG Xi-ke, SHEN Ning-fu. The Interfacial Reaction in SiCp/Al-Si Composites under Conventional Casting Condition[J]. Journal of Materials Engineering, 2003, 0(12): 18-22.
SiC/Al-5Si-Mg,10% SiC/Al-7Si-Mg (volume fraction) composites were fabricated by stirring cast. By means of TEM and EDS, investigations had been made for the interfacial reaction in re-melt composites under conventional casting condition. The SiC interfaces mainly consisted of SiC/Al interface and SiC/Si interface. With the presence of Mg in the alloy melt, particulates of MgAl2O4 were formed on some interfaces. The detrimental interface reactions of forming Al4C3 were suppressed because of Si in matrix. Different references gave different critical Si contents that avoid Al4C3 forming and the reason was explained.
JIAN Ke, CHEN Guo-min, CHEN Zhao-hui, MA Qing-song. Effect of SiC Powder Content on the Mechanical Properties of Carbon Fiber Cloth Reinforced SiC Composites Fabricated via Precursor Pyrolysis[J]. Journal of Materials Engineering, 2003, 0(12): 23-25,32.
Carbon fiber cloth reinforced silicon carbide(Cf/SiC) composites were fabricated with polycarbosilane(PCS) and divinylbenzene (DVB) as precursors and SiC as inert fillers. The effects of SiC powder(SiCp) content on the structure and properties of Cf/SiC composites were investigated. The results show that the mechanical properties of the cloth fabricated with lesser SiCp content were low because big pores existed in the composites which led to stress concentration. But when the content was excessive, SiCp would hurt the carbon fiber seriously. As a result, the properties of the composites decreased. It was found that when fabricated with 30% SiCp (mass fraction) the composites exhibited highest properties, and the flexural strength and tensile strength reached 246.4MPa and 72.5MPa, respectively.
REN Wei-hua, QIAO Sheng-ru, AO Qiang. Thermal Shock Damage Behaviour of 3D-C/SiC[J]. Journal of Materials Engineering, 2003, 0(12): 26-28.
Thermal shock behavior of 3D-C/SiC and recrystallization of SiC were investigated under two temperature drops(ΔΤ=600℃,800℃)and different stress in light-radiation thermal shock testing machine. The results indicate that thermal shock curve evaluated by Young's modulus was similar to that by electrical resistance, and they approximately consisted of three stages, that is the rapid damage stage, the stable damage stage, and then the damage sharply accelerated stage. However, exceptional thermal shock curve expressed by electrical resistance only occurred to drop in the initial stage. Moreover, thermal shock behavior of 3D-C/SiC was distinctly superior to that of recrystallization of SiC, and when the deposition time of pyrocarbon was 20h, 3D-C/SiC possessed the longest thermal shock life.
XING Li-ying, JIANG Shi-cai, LI Bin-tai. Study on the Microwave-absorbing Composite in Trap Type with Circuit Analogue[J]. Journal of Materials Engineering, 2003, 0(12): 29-32.
The "trap" type with circuit analogue was introduced into the design of microwave-absorbing composite materials. The kinds of materials used in the circuit analogue, the changing of the size of the circuit analogue and the electromagnetic parameter to influence the properties of the microwave-absorbing composite were studied for the microwave-absorbing composite materials systems in "trap" type. The results show that suitable structural design can markedly improve the microwave-absorbing and mechanical properties of the microwave-absorbing composite systems.
WANG Wen-jun, SHAO Zi-qiang, ZHANG Bao-yan. Synthesis and Characterization of Polyimide Oligmers[J]. Journal of Materials Engineering, 2003, 0(12): 33-35.
Two kinds of polyimide oligmers with amine end group were synthesized with ODA/ODPA and BAPP/BTDA respectively. The structure of the polyimide oligmers were characterized by FT-IR spectra. The weight average molecular weights of the oligmers were around 7000.Both of the two oligmers can dissolved in RS that can react with BMI.
LIU Jun-xian, WANG Ru-min, SUN Man-ling. Study on Phenolic Resin Composite Toughened by Thermoplastic Resin[J]. Journal of Materials Engineering, 2003, 0(12): 36-38.
The effect of content,end-groups and molecular weight of thermoplastic resin on properties of phenolic resin composite was investigated .The morphology of fracture was observed and analyzed with the help of scanning electron microscope. The conclusion can be drawn from the studies that the toughness of phenolic resin composite was improved by an unique two phase microstructure formed,in which the continuous net shape phase was made of thermoplastic resin, the globe shape particles of thermoset resin consisted the discontinuous phase.
JIANG Ke-juan, SHEN Jie. Thermal Oxidation Stability of Fluorosilicones[J]. Journal of Materials Engineering, 2003, 0(12): 39-41.
The anti-oxidation stability for domestic fluorosilicones with γ-trifluoro-propylmethylsiloxane structure and the function of additives were studied and discussed. The result show that metallorganic, especially ferrous-organic compounds can improve the anti-oxidation stability of fluorosilicones. And ferrous-silanol compounds also have good compatibility with fluorosilicones.
WANG Jian-ping, CHEN Liu, FENG Yu-shu. The Current Status and Prospect of Foundry Industry in China and Japan[J]. Journal of Materials Engineering, 2003, 0(12): 42-44.
Current development status of foundry industry both in China and in Japan were expound,their orientation and thought in foundry area were expound,output of each casting type and other situation in China with which in Japan in recent years was compard.
