Papers by Author: Qin Ma

Abstract: The paper deals mainly with the corrosion of 16Mn steel under the condition of three different high temperatures and in NACE solution saturated with H2S at 1MPa partial pressure of CO2, by means of autoclave, SEM, XRD, weight loss method and electron-probe micro-analysis. The result showed: under the experimental conditions, the serious CO2/H2S corrosion happened to 16Mn steel ,so that the main corrosion films, ferrous sulfide, could be clearly found on both sides of the samples; at 60°C, characteristics of pitting corrosion manifested centered chiefly around CO2 corrosion ; at 90°Cand 120°C, around H2S ones . It was the cooperating effects of both the hydrogen damage and pitting corrosion caused by CO2/H2S corrosion that formed the special corrosion features on the surface of steel to a certain degree. It was indicated that the corrosion of CO2/H2S was the result of interaction of multi-factors.

Abstract: The high energy ball milling of Ni-50 atom % Si elemental powder mixtures was carried out using a planetary mill. X-ray diffraction (XRD) was used to identify the phase evolutions during the high energy ball milling period. The microstructure morphology of the powders milled different time was determined by field emission scanning electron microscope (FESEM). The beginning time of mechanical alloying was determined by back scattered electrons (BSE) images. The XRD patterns showed that the nickel peaks intensity and the silicon peaks intensity obviously decreased with milling time increased to 1 hour. BSE images revealed that nickel and silicon powders were not blended uniformly for 1 hour of milling. It was found that NiSi formed as the milling time increased to 5 hours, simultaneously, the nickel peaks and the silicon peaks almost disappeared. That means the obvious mechanical alloying started from 5 hours of milling. BSE images agreed with the result analyzed from XRD patterns. With the milling time further increased from 10 to 75 hours, the NiSi peaks decreased gradually, at the same time, the Ni2Si peaks appeared and then increased gradually.

Abstract: The high-energy ball milling of Ni-66.7 at% Si elemental powder mixtures was carried out using a FRITSCH Puluerisette-5 mill. XRD was used to identify the phase evolutions during high-energy ball milling. The XRD patterns showed that the intensities of nickel peaks and silicon peaks gradually decreased with milling time increased from 1 h to 10 h, simultaneously, the peaks of NiSi2 and NiSi appeared. With milling time further increased to 45 h, single phase of NiSi2 formed. New peaks were observed after 75 h milling, which were indexed as FeSi. This reveals that long time high-energy ball milling will induce Fe contamination and that Fe exhibits greater activity and reacts with NiSi2 forming FeSi and NiSi. Moreover, the peaks intensity of FeSi and NiSi increased with milling time increased from 75 h to 180 h. The phase evolutions of Ni-66.7at% Si during high energy ball milling were discussed.

Abstract: The tribochemical effects of MoSi2 powder in the ball milling process have been studied by X-ray diffraction (XRD) and QM-4H milling machine. It has been found that the intensity of diffraction peak of MoSi2 powder is continuously decreased and the width increased with the increase of milling time. Specifically, the crystallite size decreased largely in the early stage of milling. Contrary to the above, the microstrain and the effective temperature factor increased considerably. After ninety hours of milling, the crystallite size had little changes. The relations among the tribochemical effect factors are as follows: the microstrain and the effective temperature factor increase with the decrease of the crystallite size. The microstrain increases with the increase of the effective temperature factor.