ZHAO Xinqing, HAN Yafang. The Kinetics of Martensitic Nucleation in Iron Based Alloys[J]. Journal of Materials Engineering, 2000, 0(3): 3-7,10.
On the basis of the classical martensitic nucleation theory, the activation energy of ho-mogeneous nucleation in iron based alloys were reconsidered.A extensive study was made to determine the dependence of activation energy on the interfacial energy and the driving force of martensitic transformation.It is indicated that thermal activated nucleation possesses very small activation energy, which is compatible with relevant experimental investigations.On this context, a nucleation mechanism was developed, attempting to explain the origin of martensitic nucleation in iron based alloys.In this mechanism, in addition to thermal activation, the contribution of mechanical driving force to the nucleation was taken into account, particular in the case of martensitic transformation at low temperature.
SUI Xiandong, LUO Chengping, OUYANG Liuzhang, LUO Zhuoxuan. A Study of Subgrain Al Layer of SiC/Al Interface in SiCp/Al-SiComposites[J]. Journal of Materials Engineering, 2000, 0(3): 8-10.
SiCp/Al-Sicomposites were studied by means of conventional TEM. It is discovered that a subgrain Al layer is usually observed at the Al side of a SiC/Al interface;the layer is less than 1μm thick and a few degrees crystallographically misoriented from the Al matrix, with high density of dislocation generated in it.Its formation might be attributed to the localized strain caused by the difference between SiC and Al in thermal expansion coefficient.
WANG Beilei, HAN Yafang, LIAO Hong. Effect of Minor C on the Vacuum Remelting Process, Microstructure and Mechanical Properties of Alloy IC6[J]. Journal of Materials Engineering, 2000, 0(3): 11-13.
In order to diminish the oxide film covering molten Ni3Al base alloy IC6 during vacuum remelting, small amounts of carbon were added.The basic composition of Ni-8.0Al-14.0Mo-0.025B(wt%)was chosen and five alloys with the different amounts of C addition(0,0.03,0.06,0.12,0.18wt%) was tested..The microstructures of the alloys have been studied by scanning electron microscopy..The tensile strength at room temperature and stress rupture life at 1100℃ have been determined. On the basis of the compromise among the microstructures, mechanical properties and the effect of C additions on oxide film, the optimum amount of C addition is determined.
LI Xijiang, RAO Xiong, ZHANG Di, SI Pengcheng. Studies on Reactions Between Aluminium/Aluminium Alloys and Molten Sodium[J]. Journal of Materials Engineering, 2000, 0(3): 14-16.
Reactions between pure aluminium/its alloys and molten sodium at 350~450℃ have been investigated Optical microcopy and X-ray diffraction analysis were used to observe and analyze the morphology, the distribution and the growth kinetic mechanism of corrosion products Experiments show that corrosion severity of specimens from molten sodium is related to the content of silicon in aluminium, and the corrosion of aluminium silicon alloy in molten sodium is a diffusion controlled solid state reaction.
LI Zhenxi, CAO Chunxiao. Effects of Trace Element of Boron on Microstructures Refinement in Ti-48Al Alloy[J]. Journal of Materials Engineering, 2000, 0(3): 17-21.
The effects of trace element of boron on microstructures refinement in Ti-48Al alloy were investigated.The results show that flaky TiB2 phases are generated after boron were added into alloys;The as cast microstructures are significantly refined when the boron additions are up to 0.8at%;During 1150℃/24h/AC heat treatment,γphase in the alloys containing boron nucleate on TiB2/matrix interfaces in addition to grain boundaries,as a result,the nearγmicrostructures are refined as nucleation sites increasing;During solution heat treatment inαsingle phase area, TiB2 phases hinderαgrains from growing very effectively, average diameter of fully lamellar grains decreases a order of magnitude with boron additions of 0.5 at%.
QU Shaobo, YANG Zupei, YU Haijun, GAO Feng, TIAN Changsheng. The Effect of Lanthanum doping on the Electrostriction and Electric Hysteresis of Pb(Zn1/3Nb 2/3)O3-based Ceramics[J]. Journal of Materials Engineering, 2000, 0(3): 22-25.
La-doped 0.85Pb(Zn1/3Nb2/3)O3-0.10BaTiO30.05PbTiO3 ternary ceramics were synthesized by the columbite method.The effect of La doping on phase structure,dieletric constant, electrostrictive properties and electric hysteresis of PZN based ceramics were investigated With lanthnum content increasing, the content of perovskite phase and dielectric constant decreased, and meanwhile dielectric temperature stability improved With the increment of lanthanum content, the electrostriction and electrostrictive coefficients decreased, and at the same time the strain and electric hysteresis decreased,i.e, remanent strain, remanent polarization and coercive fields decreased.
LU Dehong, GU Mingyuan, SHI Zhong liang, JIN Yanping. Effect of the Fraction of SiC on the Wear and Friction Performance of Silicon Carbide and Graphite Particulates Reinforcing Aluminum Matrix Composite[J]. Journal of Materials Engineering, 2000, 0(3): 26-28.
The effect of the fraction of SiC on the wear and friction performance of silicon carbide and graphite particulates reinforcing aluminum matrix composite was investigated.The wear rate of Al/SiC+Gr volume was found to decrease with fraction of SiC from 10vol% to 20vol%, and reach a valley value at 20vol%, then ascend with fraction of SiC from 20vol% to 40 vol%.The analysis shows that the increase of the fraction of SiC leads to change in two mechanical properties of Al/SiC+Gr One is increase of hardness;the other is decrease of plasticity When the fraction of SiC is less than 20vol%, the effect of hardness increase of Al/SiC+Gr on the wear performance is more than that of decrease of plasticity, so the wear rate of Al/SiC+Gr increases with the fraction of SiC Otherwise,the effect of plasticity decrease on the wear performance of Al/SiC+Gr is more than that of hardness increase, so the wear rate of Al/SiC+Gr decreases with the increase of the fraction of SiC.
FAN Yongzhong, SUN Kang, WU Renjie. Study of Epoxy Resin Composites Damping Properties and Its Application to the Noise Reduction[J]. Journal of Materials Engineering, 2000, 0(3): 29-35.
The damping measurement of composite materials indicates that glass fiber(GF) and carbon fiber(CF) in hybrid composites have reverse contribution to the ultimate mechanical and the damping properties. It shows that a balance between the modulus and the damping factor can be reached by careful selection of the resin matrix and fiber category, fiber volume and hybrid layer design.The paper provides the information about the possible application of composite materials to the low noise and lightweight propeller, whose actual mechanical and damping requirements can be satisfied rigorously through proper material design.
YAN Feng, WU Kun, ZHAO Min. Superplasticity of SiCw/MB15 Magnesium Matrix Composites[J]. Journal of Materials Engineering, 2000, 0(3): 32-35.
The superplastic characteristics of SiCw/MB15 magnesium matrix composites were investigated.The results show that the SiCw/MB15 magnesium matrix composites exhibit a total elongation of 200% and mvalue of 0.35 at the initial strain rate of 1.66×10-2s-1and at 340℃.There are many cavities and cracks in matrix, and whiskers are randomly arranged after superplastic deformation while they are oriented to the extrusion direction before superplastic deformation This phenomenon suggested that the matrix grain boundary sliding should take place during the superplastic deformation.
ZHENG Yongting, HAN Jiecai, ZHANG Xinghong, DU Shanyi, HE Xiaodong. Raction Synthesis of Y2O3/AlN Ceramic and Mechanism of Densification[J]. Journal of Materials Engineering, 2000, 0(3): 36-38,48.
Compact AlN/Y2O3ceramics were fabricated by combustion synthesis of Al particles in the super high pressure nitrogen(1000atm).In the SHS process of AlN2 Y2O3 system,when the temperature was up to 1760℃,eutectic melt Y3Al5O12was formed from Y2O3and Al2O3,then liquid sinter occurred With increasing of Y2O3content in the original powder system, porosity of the products decreased,content of the plastic Al in the products increased, then bending strength and fracture toughness increased In AlN2Y2O3>system, SHS densification have apparent tropism, mainly occurred along the combustion front.
ZHOU Xingui, ZHANG Changrui, HE Xinbo, LI Yinkui, ZHOU Anchen, CAO Yingbin, MA Jiang. A Study on the Hot Press of Pyrolysised Carbon Coated Carbon Fiber Reinforced Silicon Carbide Composite[J]. Journal of Materials Engineering, 2000, 0(3): 39-41.
The continuous carbon fiber reinforced silicon carbide ceramic matrix composites were fabricated through hot press methods, using pyrolysised carbon coated carbon fiber M40JB as reinforcement and polycarbosilane as precursor.The properties of Cf/SiC composite were tested and compared.The microscopy structure was characteristic by SEM and TEM at the same time.The results show that the pyrolysised carbon coating have evident effect on the properties of Cf/SiC composite, the hot press temperature 1850℃ and pressure 25MPa is suitable.
ZHANG Zhongtai, LIN Yuanhua, TANG Zilong, ZHANG Junying. Nanometer Materials & Nanotechology and. Their Application Prospect[J]. Journal of Materials Engineering, 2000, 0(3): 42-48.
The properties of electronics, mechanics, magnetics and optics of nanometer materials were changed greatly because of their particular surface effect, volume effect and quantum size effect Nanotechnology was applied successfully to fine ceramics, microelectronics, bioengineering, chemical engineering and pharmacy fields.Its widely applied prospect made nanometer materials and corresponding nanotechnology become one of the hot topics in the scientific research field, which have great improvements on the materials'super-plasticity and high-strength, these characteristics have significant effects on the electronics, thermal dynamics, magnetics and optics of materials, they are regarded as another industrial revolution in the 21th century.
