Advanced Materials Research Vol. 1094

Abstract: High energy ball mill tests under the condition of the ball material mass ratio 13:1 and the rotate speed 400 r/min have been employed to investigate the process of mechanical alloying (MA) of Ta and Cr powder mixed in the mole ratio of 1:2.The microstructure evolution process and phase composition were explained useing scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that, the milled 20h powder existed in Ta (Cr) supersaturated solid solution and amorphous after 40h. Although the hours were spent on ball milling reached to 50h, Laves phase TaCr₂ had not been made during the process.

Abstract: Zirconia ceramic and titanium alloy were jointed by using an AgCuTi amorphous alloy as a solder. The microstructure and the properties of the joint are investigated. The results show that the microstructure and mechanical properties of the brazing seam are influenced by the brazing temperature, the heat time and the cooling rate. The shear strength of the joint decreases with increasing of the brazing temperature, the heat time and the cooling rate increase. The maximum shear strength of the joints reaches 178 Mpa. The optimal technical parameters are the brazing temperature of 1123 K, the heat time of 10 min and the cooling rate of 5 K/min.

Abstract: To improve the performance of NM400, V, Ti and Ce were added in NM400. The effect of alloy on grain size, precipitation, hardness and toughness was studied. The result shows that V and Ti can improve the performance by grain refiner and dispersion-strengthening. By further adding Ce, the size of grain and precipitations of V and Ti is significantly reduced, the solid solution quantity of V and Ti and the amount of precipitation are increased, and the precipitation shape transforms from cube to sphere. Therefore the hardness and toughness of steel are greatly improved. In this study, 0.2% V and 0.2% Ti were added into NM400. As a result, the precipitation of V and Ti, in form of carbide and nitride, was the smallest and dispersed, and the grain size was the smallest, which leaded to the best performance. The conclusion is that, to ameliorate the performance of NM400, the optimal additive amount of V and Ti is 0.2% no matter whether adding Ce or not.

Abstract: EIS technique was employed to study corrosion of the rusted cast iron artifacts in seawater. The impedance spectra show characteristic of diffusion in the complex plane. At low frequencies, the complex impedance data trace out straight lines with less slopes with increasing immersion time. Equivalent circuit provides useful information that the rusted iron undergoes severe corrosion in seawater in the presence of porous scale. SEM results reveal the morphologies of the three main iron oxyhydroxides.

Abstract: High Current Pulsed Electron Beam (HCPEB) was employed to treat Ti-6Al-4V alloy subjected to micro-arc oxidation. The surface morphology and phase composition of surface film were investigated, as well as the wear and corrosion resistance. The results show that the coarse porous ceramic coating becomes smooth and compact after electron beam treatment. High temperature stable rutile phase increases, and low temperature stable anatase phase reduces. The friction coefficient of composite coating reduces obviously and stabilizes at 0.2, and the wear resistance is improved. The increased corrosion potential and decreased corrosion rate exhibits an enhanced corrosion resistance.

Abstract: The external desulphurization of molten iron has become an important step in the production of steel and iron. The melting temperatures of high calcium desulfurization slag, which were taken from Shougang Shuicheng Iron and Steel (Group) Co. Limited, were investigated on basis of the method of hemisphaerium temperature. The contents of CaO, Al₂O₃ and CaF₂ in the slag were adjusted in 47%-53%, 14%-20% and 2%-10% respectively by adding analytical reagent Ca (OH)₂, Al₂O₃ and CaF₂ using orthogonal design. The results show that the melting temperature of desulfurization slag decreases obviously with the increase of the content of Al₂O₃ between 14% and 20%, and decreased markedly with the increase of the content of CaF₂ lower than 8%. The impact to the melting temperature of the high calcium slag is as follows: Al₂O₃ > CaF₂ > CaO.

Abstract: A 3D Finite Element Model of the Temperature Field for Electron Beam Cladding of Pre-Tungsten Powder on the Surface of the Copper Block was Established, According to the Actual Situation of the Electron Beam Cladding Process, Based on Finite Element Analysis Software ANSYS Workbench, Analyzed the Temperature Field Distribution of the Electron Beam Cladding Process. Temperature Field Calculation Results Showed that the Cladding Process Heating and Cooling Speed was up to 10³-10⁴°C/s, and the Surface Temperature Increased Rapidly, while the Temperature of the Substrate Maintained Low, since the Water Cooling System.

Abstract: In this paper, a new high precise powder feeder designed for fabricating functionally gradient metal component was presented. The mechanism, control principle and computer control program of the powder feeder were introduced and the powder feeding precise test experiments were carried out with Ni-based alloy powders, Fe-based alloy powders and ceramic powders in the particle average diameter of 15-350 Microns. Experimental results showed that the powders mixtures obtained from the high precise powder feeder are continuous and stable. The precision of delivering powders mixture can be weighed within 2% error scope comparing to the desired mixture quality and the flexible proportion of different powders mixture can be easy changed in the computer control program by synchronously controlling the powder feeder motor’s rotation speed.

Abstract: Ultrasonic shot peening (USP) on AALY12 sheet was studied. Several parameters (arc heights, surface roughness, surface topography and micro hardness) with different USP process parameters were measured. The research proposes that radius of curvature of shot peened sheet increases with time and electric current decreasing, while increases with pin diameter increasing, and radius of curvature reaches a saturation level after a specific processing time and electric current. An empirical model of the relationship between radius of curvature and pin diameter, electric current, time was also obtained. The research shows that the increment of surface and vertical micro hardness of material is more obvious with longer time and higher value of electric current, which can be up to 20% and 28% respectively.

Abstract: The new extrusion route of ECAP which is called route 135 was put forward in this paper. The grain refinement of the traditional extrusion route B_C and the new route of ECAP process in 99.9995% (5N5) high purity aluminum was compared using a die with a channel-intersection angle 90°. It was found through experiment that, the grain was very coarse in the cast ingot of 5N5 high purity aluminum, and the average grain size is about 60mm. High purity aluminum processed by one pass ECAP was refined notably, and average grain size is about 1000 μm. After two ECAP passes, the average grain size is 200μm with route B_C, while it is less than 50μm with route 135. The refinement of two passes of route 135 is equivalent to the refinement of eight passes of route B_C. It indicates that the route 135 is more effective than route B_C. TEM micrograph of 5N5 high purity Al with different ECAP pass under route B_C and route 135 was studied.