Xiao Xue-shan

Effects of Multi-Scale Microstructure on Pitting Corrosion and Mechanical Properties of High-Mn-N Low-Ni Superduplex Stainless Steel

Abstract A high-Mn-N low-Ni superduplex stainless steel 25Cr-2Ni-3Mo-10Mn-0.5N with multi-scale microstructures has been prepared through severe cold rolling and annealing, and the effects of multi-scale grains on the pitting corrosion and mechanical properties have been investigated. The results show that the multi-scale microstructures have a strong relation with the annealing time, that is, the average grain sizes of austenite and ferrite increase with prolonging of the annealing time at 1050 °C, they have the minimum values of 1.5 and 7.18 μm, respectively, when the alloy is annealed for 1 min. The tensile strength, yield strength and reduction in area of the sample decrease with the growth of multi-scale grains, whereas the pitting corrosion resistance of the specimen is enhanced. The multi-scale microstructures play an important role on the pitting corrosion and the mechanical properties of superduplex stainless steel 25Cr-2Ni-3Mo-10Mn-0.5N.

The phase transition of syndiotactic polystyrene induced by electrostatic field

The crystal structure and morphology of syndiotactic polystyrene (sPS) melt-crystallized in various electrostatic fields have been investigated by using wide angle X-ray diffraction (WAXD), differential scanning calorimeter (DSC) and scanning electron microscope (SEM). WAXD and DSC analyses show that sPS is gradually transformed from a phase to β phase with increase of electrostatic intensity. The SEM observations indicate that the morphology of sPS micro-crystals is strongly dependent on electrostatic intensity applied to the sample during solidification. The variation of the micro-crystals orientation from disordered lamellae to ordered lamellare have been observed with increase of electrostatic intensity.

Investigation on crystallization kinetics of Zr-Al-Based bulk amorphous alloys

Zr86Al10Ni10CU16, Zr62.5Al10Ni10Cu15Be12.6 and Zr52.6 Al10Ni14.4Cu17.6Ti6 bulk amorphous alloys were prepared by copper mould casting. The crystallization kinetics was measured by differential scanning calorimeter(DSC) with different heating rates, and the activation energy was calculated using Kissinger equation. The relationship between thermal stability and rate constant of crystallization reaction is discussed on the view of crystallization kinetics, and the effect of small atom Beryllium on thermal stability of bulk amorphous alloys is also studied.

Influence of rolling temperature in supercooled liquid region on the surface morphology of Zr52.5Al10Ni10Cu15Be12.5 bulk metallic glass

Surface morphologies of Zr52.5Al10Ni10Cu15Be12.5 bulk metallic glass after being rolled at both a temperature around Tg and near (Tx−50) K were investigated with a scanning electron microscopy. Macroscopic and microscopic observation results show that squamae, cracks, steps and wedges exist on the surface when the samples were rolled at temperatures around Tg. However, a smooth and flat surface appears when the samples were rolled at temperatures near (Tx−50) K. These results indicate that the mode of deformation in the supercooled liquid region is a partially homogeneous flow at a temperature around Tg, and a fully homogeneous one at temperatures near (Tx−50) K. According to the results, it is more feasible to roll the amorphous alloys at temperatures near (Tx−50) K to obtain parts with smooth and flat surface.

Curie temperature of the intergranular amorphous phase in nanocrystalline Fe89Zr7B4 alloy

The FeZrB amorphous alloys for simulating the intergranular amorphous phase in the nanocrystalline Zr7B4 soft magnetic materials were obtained by mechanical alloying of a mixture of elemental Fe, Zr and B powders for 25 h. It is shown that the Curie temperature of the simulated intergranular phase alloy is much lower than that of the intergranular phase with the same chemical composition in the nanocrystalline Fe89Zr7B4 alloy. The possible mechanism is mainly due to the strong ferromagnetic exchange force among the nanocrystalline α-Fe grains.

Effect of Electrostatic Reduced-Gravity Environment on the Crystallographic Parameters of Melt-Crystallized Polypropylene

An electrostatic reduced-gravity device was developed and used specially for the study of the melt crystallization of polypropylene. The crystal structure of melt-crystallized polypropylene prepared under the reduced-gravity environment was investigated by using X-ray diffraction. The experiment results show that the crystal structure of the polypropylene is strongly dependent on the gravity applied to the sample during solidification. It is found that the crystallographic parameters a and b increase markedly with reduced-gravity ratio, while the value of c increases mildly.