Papers by Author: Qing Chao Tian

Abstract: Preparation of Mn-Cu based damping alloy ingots coupled with strong magnetic fields shows many interesting phenomena on the solidification microstructure and the crystal lattice. In this study, modified M2052 ingots were prepared under different magnetic fields to investigate the bulk solidification behavior by using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Metallographic analysis reveals that the deflection angle of the primary dendrite arm increases with the increase of magnetic field strength. The distribution of chemical composition characterized by X-ray Fluorescence discloses that Mn is enriched while Cu is depleted along the circumferential surface side, and the variation tendency changes from almost a level to a sloping line under applied magnetic field. High magnetic field have altered the orientation of the γ-Mn dendrites from (200) to (111), and the coupling mechanism of alloy solidification with strong magnetic field is discussed based on the experimental results.

Abstract: The welded joint of a S890QL grade steel pipes containing 1.2% Ni have been prepared to characterize the use performance under high cycle fatigue test. It has been found that the fatigue strength of the welded joint is 290MPa with a fatigue life of more than 10 million cycles, and the obtained Basquin equation is σa=488*(2N)-0.02758 . It is found that the steel exhibits the whole bainite microstructure when the cooling rate is less than 1°C/s. The welded joint is divided into the weld zone, the coarse grain zone, the fine grain zone, the softening zone and the matrix. The fine grain characteristic in the welded area determines the good anti fatigue performance of the investigated steel.

Abstract: Electrochemical measurement techniques were applied to investigate the polarization and hydrogen permeation behavior of Cu-bearing CrMo steel in a H2S saturated aqueous brine solution. The observation on microstructure and precipitate phases of the steel was conducted by transmission electron microscopy (TEM), and the corrosion product was investigated by using X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). It is disclosed that copper addition could effectively influence the electrochemical behavior of the investigated steel, and the dissolution behavior of iron matrix and carbide precipitates in the H2S solution acts as a key role for the steel resistance to hydrogen sulfide corrosion.