Advanced Materials Research Vols. 399-401

Abstract: The corrosion behavior of the anodic oxide film on aluminium 7A04 alloy is investigated in current paper, where the different anodic oxide films are prepared. Morphology observation on different anodic films is carried out by using laser confocal microscopy (LCM) and copper sulfate test. Meanwhile, the electrochemical properties are evaluated through using electrochemical impedance spectroscopy (EIS). The LCM observation shows that the anodic oxide film formed in boric/sulphuric mixed acid is uniform with porous appearance, while the anodic oxide film formed in chromic aid is nonporous one but defective. The copper sulfate test results show that the corrosion regions almost developed from micropores in strong corrosive media. The evaluation of EIS in NaCl solution demonstrates that the corrosion resistance of specimen with anodic oxide film is much better than that without film. Furthermore, the corrosion resistance of anodic film formed in boric/sulphuric mixed acid is better than that formed in chromic acid.

Abstract: The behavior of 3d electrons and microdefects in binary Ti-Al alloys with Al contents from 47at.% to 53at.% have been studied by coincidence Doppler broadening and positron lifetime techniques. It has been found that the 3d electron signals in the spectra of binary Ti-Al alloys increase with Ti content. In Al-rich Ti-Al alloys, on increasing Al content, the open volume of defect on grain boundary increases while the density of free electron decreases. On the contrary, in Ti-rich Ti-Al alloys, on increasing Ti content, the open volume of defect on grain boundary decreases, and the electron density of the grain boundary increases.

Abstract: Mo powder was pressed into rods by cold isostatic pressing and sintered by multi-function furnace. Physical and chemical properties of sintering samples at different temperature were tested such as chemical elements, density, area shrinkage ratio and fracture surface morphology. Through the investigation we can draw the conclusions as following: Mo powder softens at 1353K. The temperature of beginning metallization is 1833K. In the range of 1713K~1953K, impurity contents such as C and O drop down fast and density increases sharply. When sintering temperature rises from 1833K to 1953K, the grains of sintering rods are fine. When the sintering temperature surpasses 2073K, the grains grow up very fast. The sintering shrinkage ratio enlarges quickly.

Abstract: Abstract. In order to enhancing strip flatness in temper mill, in this paper, stress state, micro structure characteristics of contact surface, energy characteristics, dislocation intensity were analyzed. Plastic deformation characteristics of metal during tempering process have been come to a conclusion. Two mechanisms, friction mechanism and elongation rate mechanism, are proposed for enhancing strip flatness during tempering process. On the basis of these mechanisms, strip flatness control strategies suitable for tempering of ordinary cold rolled products, cold rolled deep-draw products, hot rolled products and hot rolled high strength steel products are discussed, and proper equipment configuration is proposed.

Abstract: Contrastive analysis on recrystallized strips of high permeability grain-oriented silicon steel by inherent and acquired inhibitor method has been done, including structure, grain size, coincidence site lattice（CSL） and texture. Results show that the mean primary grain sizes of high permeability grain-oriented silicon steel by inherent inhibitor method and acquired inhibitor method of this experiment are 12.66μm and 27.95μm, respectively. The former is homogeneous structure while the latter is coarsened to some extent. Both primary recrystallized strips have equivalent percentage of ∑9 boundary, but the strip by acquired inhibitor method has higher percentage of ∑3 boundary than that by inherent inhibitor method. Both primary recrystallized strips have {111}<112> as the main texture component, however, the strip by acquired inhibitor method has（113）[5，-11，2] texture component, which is not desirable for ideal secondary recrystallization texture.

Abstract: The electrochemical behavior of electrolytic tinplates was studied and analyzed by means of electrochemical methods together with tin quantity test and scanning electron microscopy (SEM). The results indicated that the properties of the Sn-Fe alloy layer determined the electrochemical behavior of electrolytic tinplates. The electrolytic tinplate possessed higher corrosion resistance if the Sn-Fe alloy layer was thicker and more compact.

Abstract: Hadfield steel is wear-resisting steel and widely used where the devices have high impact wearing performance requirements. Cold asynchronous rolling technique can improve the mechanical performances of high manganese steel to a certain degree. Through experimental research, this paper studied the effect of deformation degree and diameter ratio on its mechanical performances during asynchronous rolling.

Abstract: Electrochemical impedance spectrum (EIS) technology and microscope analysis were used to investigate the corrosion behaviors of X70 pipeline steel in 0.5 M NaHCO₃ + 0.5 M NaCl mix solution. The effects of applied stress on the open circuit potential (OCP), polarization resistance and surface microscope were summarized. The results show that OCP of X70 steel decreased linely with applied stress increasing. The polarization resistance also decreased with the increase of stress. The electrode reaction on X70 steel surface changed from activation control to diffusion control and mixed control and corrosion resistance of X70 pipeline steel declined. The number and the diameter size of pit on the sample surface increase with applied stress increasing.

Abstract: In the present study, X80 and X100 grade high deformability pipeline steels have been processed by using TMCP and followed two-stage cooling process. The microstructures of the X80HD (HD, high deformability) and X100HD steels were both characterized by ferrite-bainite dual phase. The grains sizes of ferrite were mostly less than 5μm and the volume fractions were about 20~25% in X80HD and 10~15% in X100HD steel. The bainite structure in X80HD steel was granular bainite (GB); while in X100HD steel large amounts of lath bainite (LB) were also formed besides GB, and bainite grains were much finer. Ferrite-bainite dual phase microstructure has large strain hardenability that resulting high strength and high deformability combination. Both the steels exhibit high strength/toughness in transverse direction and high deformability in longitudinal direction. The X100HD steel with more volume of LB and less volume of PF has higher strength but lower deformability than that of X80HD steel.

Abstract: Microstructure evolution of Fe-1.18%Cu high purity steels during solution and aging was investigated under high-resolution electron microscope (HREM). In addition, the aging strengthening mechanisms were discussed based on the microstructure observation. The results show that there were lots of Cu atom clusters in ferrite matrix during solid solution and aging initial stages, subsequently, Cu-rich metastable Fe-Cu particles precipitate at the aging strength peak. It is found that the intense strengthening is controlled by the coherency relationship of Fe-Cu metastable phase with matrix that forms the obstacle of the dislocation motion, while the decrease of strength after the peak is attributed to the loss of coherency, which should highly likely be the dominant reason of aging strengthening in Cu bearing high purity steels Thus our TEM observation results are in reasonably agreement with some previous assume.