Applied Mechanics and Materials Vols. 268-270

Abstract: Being compared with traditional wear resistant materials, the corrosion resistance of high boron iron-based alloy at 25°Cand at 60°Care researched respectively. The results show that the corrosion resistance of wear-resistant alloys decline at high temperature. At 25°C and at 60°C, though the corrosion resistance of high chromium cast iron is a little higher than that of high boron iron-based alloy in acid medium (PH=3), high boron iron-based alloy’s corrosion resistance is the best among these three materials in neutral medium (PH=7) and in alkaline medium (PH=12).

Abstract: The corrosion behavior of extruded Mg-1Ca-0.5Mn（weight percent）alloy in 0.9% sodium chloride water solution was investigated by using mass-loss measurement and electrochemical method. The results show that filiform corrosion and pitting corrosion occur during immersion corrosion process. The average corrosion rate gradually decreases as immersion time increases; it is 0.53 mm/a after immersion at 37°C for 11 days. The corrosion current density i_corr and corrosion potential E_corr of the alloy is 0.042 mA/cm² and -1.60V, respectively. The instantaneous corrosion rate is 0.88 mm/a. Mg-1Ca-0.5Mn alloy erodes by continuous dissolution. The corrosion product Mg(OH)₂ layer surrounding the magnesium alloy can decrease the corrosion rate. The erosion process of the magnesium alloy is controlled by cathodic diffusion.

Abstract: A physics model was established for describing the particle size distribution of beryllium (Be) powder produced by impact attrition milling. In this model, two factors were considered: the first, the distribution of existing state of particles with different original kinetic energy should obey the Maxwell-Boltzmann statistics after impacted, it was that, being at higher energy level made big particles unstable, which were easy to be fractured into smaller pieces in impact attrition process, this influencing factor described as the negative exponential of particles size; the second, the tendency to remain low surface energy needed particles should keep big volume as much as possible, this effect defined as the cube of particles size. The actual particle size distribution of Be powder was resulted from the competition between these two factors. Calculating result from the model was in good agreement with data from measurement.

Abstract: In this paper, the WC-16TiC-xTaC-9Co and Co are mixed together preparing for WC, (W, Ti, Ta) C. By high-energy ball milling, the powder is cold isostatic pressed and vacuum sintered by 1410°C, 1430°Cand 1450°C.The physical properties and the micrographs of samples are detected. The main conclusions are as following: sintered samples have the best comprehensive performance at 1450°C, the density of the sample is 99.7% and the actual density is 10.91g/cm3. The hardness is 92.8 HRA and the transverse rupture strength (TRS) is 1100MPa. The grain size grows up obviously with the high temperature. The average grain size of WC is 0.7μm and the average size of (W, Ti, Ta)C is 3μm.

Abstract: Multi-fractal theory is used to detect fractal behaviors embedded in grain size distribution ofsinter with low SiO2. Impacts of SiO2, basicity, and MgO on structures of sinter ore are measured quantitatively by means of fractal dimension dm, d(1) and multi-fractal strength Δd. Increase of SiO2 induces decrease of fractal dimension and multi-fractal strength. While proper levels of carbon, basicity, and MgO lead to minimum values of fractal dimension and multi-fractal strength. This kind of quantitative measurement of structures in sinter ore can help us to investigate the relation of mechanical properties and structures in a quantitative way.

Abstract: Three different analysis methods was put forward to carried out aircraft aluminum alloy structure corrosion damage forecasting,and comparison analysis of different method which included basic forecasting caculation principle and forecasting accuracy and forecasting extensionality also was discussed.The forecasting calculation result shows that the prediction accuracy of neural net and time series method is higher than the data fitting method,and the prediction extensionality of time series method is the best among the three method which discussed.

Abstract: The phase-field model coupling with the concentration field and flow field was used to simulate the dendrite growth during isothermal solidification of Fe-C alloy in a forced flow. The effects of anisotropy modulus and anisotropy strength on the dendrite growth are studied. The results indicate that the dendrites have four preferential growth orientation and the side-branches growth is not perpendicular to the primary branch while the dendrite along with crystallographic directions. When the dendrite along with crystallographic directions, the dendrites have six preferential growth orientation and the side-branches are parallel to the neighborly primary branch. At a anisotropy strength of 0.01, the crystal have no apparent principal branch and grows into coral shapes.With an increase in anisotropy strength, the tip solute concentration decreases, makes the dendrite growth become fast, the tip velocity increased continuously.

Abstract: A comprehensive mathematical model of full oxygen blast furnace with top recycle gas heated by gasifier was established. The model consists of the calculation equations for gas composition of four zones (hearth, belly, lower shaft, top) in the blast furnace, the thermo-chemical balance model of blast furnace, the energy balance model of hot stand-by zone of blast furnace, the shaft efficiency model of blast furnace, the calculation equations for gas composition of gasifier and the thermo-chemical balance model of gasifier. By using this model, the new process was calculated. The results show that coke rate and coal rate of the new process are 200 kg/thm and 190 kg/thm respectively, fuel rate is decreased by 24.7% compared with that of conventional blast furnace. In addition, theoretical combustion temperature decreases with increasing hearth-recycle gas quantity. Increasing of hearth-recycle gas quantity by 10 m3/thm decreases theoretical combustion temperature by 11.6 K. Furthermore, the model could be applied to calculate the operating parameters when the raw materials and fuel conditions are different, and the changing laws of operating parameters under the same raw materials and fuel conditions could also be studied with this model.

Abstract: Mg-1Si alloy doped with 1%Y was prepared by in-situ reaction synthesis. The effect of hot extrusion on the microstructure and elevated-temperature mechanical properties of the alloy was studied. The microstructures were analyzed by optical microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffractometry. The results show that as-cast Mg-1Si-1Y alloy consists of dendritic α-Mg phase, eutectic needle-like Mg2Si phase and Mg24+xY5 phase precipitated from α-Mg, Mg2Si can be modified and refined by yttrium, and α-Mg grains can be refined by dynamic recrystallization occurred in hot extrusion process. The tensile strength and elongation of the alloy at ambient temperature are improved prominently by hot extrusion. The tensile strength and elongation of the extruded alloy is 185.3MPa and 24.3% at 120°C. The improved elevated-temperature properties of the alloy are ascribed to the fine-grained strengthening and dispersion strengthening from Mg2Si and Mg24+xY5 particles.

Abstract: In order to investigate the effect of continued equal channel angular pressing (ECAP) with different routes and passes on the homogeneity of structure, the process of continued ECAP for pure aluminum bar was simulated by DEFORM-3D software. It obtains the load-stroke curves for different passes, distribution of effective stress and effective strain in different routes after the sample is extruded eight passes by ECAP in routes A, BC and C. The results show that the uniformity of the sample is improved with the increase of passes. The microstructure of specimen which is extruded in route BC is the most uniform, but it is the worst in route A.