Alloying element Si can improve the high-temperature creep resistance of the Ti-rich TiAl intermetallic compound. Numerous Ti_(5)Si_3 phase, precipitated as hexagonal foils along the γ-γ and γ-α_2 interfaces in the lamellar structure, was observed by TEM on the hot isostatic pressing TiAl-V-Si alloy compact. The orientation relationships between this precipitating phase and the TiAl and Ti_(3)Al phase are as follows:[0001]_(Ti_(5)Si_3)Correspondenl: HE Lianlong,research assistant , Institute of Metal Research, Chinese Academy of Sciences,Shenyang 110015

The microstructures of as-cast and annealed ribbons of the RS Al-Fe based alloys have been studied by TEM and energy dispersive X-ray spectrometer. Microstructure of the cross-section ribbons revealed as three areas: with or without quasicrystalline phase and with decomposed quasicrystalline particles.The quasicrystalline in the middle area began to crystallize during annealing at 698 K for 1 h and the resultant microstructure is similar to that of as-cast free-side section,indicating that the crystallization of quasicrystalline phase occurred during solidification and at the interface between quasicrystalline phase and matrix.Correspondent: GUAN Shaokang, Research Centre for Materials, Zhengzhou Institute of Technology,Zhengzhou 450002

The microstructures of Al-3.1 8Ti-0.65C alloy DC-casting and melt-spun have been characterized using TEM, EELS and X-ray diffraction. The DC-casting microstructure comprises a separate array of TiC phase particles, needle-like phases Al_(3)Ti and Al_(3)Fe in an aluminum matrix.In the melt-spun, uniform and fine-scale dispersions of intermetallic phase are single TiC phase(NaCl structure type, α_0=0.432 nm) with a composition consistent TiC_(0.76),while the needle-like phases are inhibitted. Based on the result, the formation mechanism of TiC is discussed.Correspondent:TONG Xingcun, Research Center for Materials, Zhengzhou Institute of Technology,Zhengzhou 450002

Compositionally modulated Fe-Dy films were prepared by alternate evaporation of the two elements onto Si single crystal substrates. Atomic ratio (Fe:Dy) of the film is about 3: 2. Auger electron spectrometry (AES), Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), and measurements of magnetic properties were used to study the changes of the films after Ar ion beam mixing.The ion energy and the dose range were 110 keV and 5×10~15-1×10~(17)cm~(-2); respectively. It was found that, complete mixing of the films can be achieved at an ion fluence of1×10~(17)cm~(-2). At this point, the films transformed from a mixture of crystals to an amorphous alloy completely. The saturation magnetization M_s of the films decreases after ion beam mixing. In particular, M_s drops sharply for the ion fluences being equal to or less than 5 × 10~15 cm~-2.Correspondent: WANG Peixuan, professor,Department of Material Physics, University of Seience and Taohnology Beijing, Beijing 100083

The isothermal low-cycle fatigue behaviour of 62Sn-36Pb-2Ag surface mount solder joint under shear stress has been discussed, meanwhile, the curve of shear fatigue life vs cyclic shear stress amplitude has been obtained, and the failure mechanism under different shear stress amplitude at different temperatures is analyzed. The results show that:there are obvious cyclic creep behaviour during constant stress amplitude low-cycle fatigue in 62Sn-36Pb-2Ag surface mount solder joints. The failure of solder joint is due to the interaction of fatigue and creep. At 25℃, under low shear stress amplitude, the failure is controlled mainly by fatigue mechanism, in constrast, under high shear stress amplitude, controlled mainly by creep mechanism:the failure mechanism at 100℃ is similar to that at 25℃ , only the transfer stress τ_(+) from fatigue mechanism to creep mechanism is lower than that at 25℃. Under similar relatative shear stress amplitude (τ_(+)/τ_b and τ_(+)/τ_b＇), the fatigue rack propagation rate da / dN at 100℃ is similar to that at 25℃ .Correspondent: LI Yunqing, lecturer, Department of Materials Science and Engineering, Tsinghua University,Beijing 100084

A new non-linear accumulate damage model was derived from the concept of equal failure probabilities under different stress levels. Based on this model,a method of calculating fatigue reliability under complex loading was obtained when the fatigue life is obeying logical normal distribution. At last, the calculating formulas were discussed when the P-S-N curve is described as a power function or an exponential function.Correspondent: HAN Yumei, research assistant, Institute of Corrosion and Protection of Metals, Chinese Academy of Sciences, Shenyang 110015

Studies were made on the fatigue strength of the extruded 16 v.-% SiC whiskers reinforced LD2 composite with two varieties of whisker orientation and two regimes of aging. Observations on their microstructure before or after fatiguing and on fatigue fracture surfaces were carried out under TEM and SEM.Experimental results show that the composite has a superior high-cycle fatigue strength to the unreinforoed alloy, especially, of the longitudinal orientation in comparison with transverse one.Correspondent:WANG Dezun, associate professor, Harbin Institute of Technology, Harbin 150006

A contact explosion technique is developed using PETN compact powder explosive to study the fracture behaviour of 93W-4Ni3Fe W alloy at high strain rates. The fractograph exhibits a strong feature of brittle type. This fact is because of greater increase in W-W fracture interface at high loading rates in comparison with the existing results in quasi-static test.Correspondent. LIU Xiaoping, Institute of Mechanics, Chinese Academy of Sciences, Beijing 10080