Band 112, Heft 3

The distributions of arsenic, lead, tin and zinc between iron silicate slag and copper in equilibrium with tridymite in the Cu–Fe–O–Si system have been experimentally determined at selected oxygen partial pressures ( P (O 2 )) at temperatures of 1 523 K and 1 573 K. The experimental technique involved high temperature equilibration in a sealed silica ampoule to minimize the vaporization of minor elements, rapid quenching of the condensed phases, and the direct composition measurements of the condensed phases using microanalysis techniques. The effective P (O 2 )s of the samples were determined based on the measured Cu 2 O concentrations in slag. The new experimental data resolve discrepancies found in previous studies and have been used in the development of a new thermodynamic database of the Cu–Fe–O–Si system containing minor elements.

This paper describes the optimal selection of chopped strand mat glass-fiber-reinforced unsaturated polyester resin (CGRP) polymer matrix composite (PMC) by considering the strength and stiffness of various composite samples. The two-, four-, six-, eight- and ten-layered CGRP-PMC samples were prepared by using a hand-layup method. Then, the natural frequency and damping ratio of the CGRP-PMC samples were determined through experimental free vibration analysis using DEWESoft software. The density, tensile strength, flexural strength, impact strength, absorbed energy, inter-laminar shear strength, and fracture toughness results of the CGRP-PMC samples were considered as attributes for the selection of the optimal composite using multi-attribute decision making (MADM) techniques. The six-layered CGRP-PMC material was selected as the optimal PMC based on the results of MADM techniques.

The present work deals with the outcomes of a novel approach for developing a multi-walled carbon nanotube-reinforced hybrid aluminium metal matrix composite. Microwave hybrid sintering in combination with cold compaction of the powder metallurgy route was followed for the fabrication of composites. Microwave hybrid sintering was carried out using a microwave oven operating at 2.45 GHz frequency and 900 W power. For this purpose, Al5083 was used as the matrix material, and silicon carbide (15 wt.%) and multi-walled carbon nanotubes (0.5 wt.%) the reinforcements. The fabricated composites were then characterized by hardness, microstructure, and porosity. An investigation on the wear resistance of the base alloy and the conventional and microwave sintered composites followed this. The findings of the present study reveal the fact that the addition of carbon nano-tubes in the composite and the use of microwave energy over conventional sintering have a significant effect on the property enhancement of the developed hybrid composite.

According to the microstructural evolution during longterm thermal exposure at 1100 ° C, the creep rupture life of Ni-based single crystal superalloys at 980 ° C/270 MPa was evaluated. The microstructure was characterized by means of scanning electron microscopy, X-ray diffraction and related image processing methods. The size of γ ’ precipitates and the precipitation amount of topologically close-packed increased with the increase in thermal exposure time, and coarsening of the γ ’ precipitates led to the simultaneous increase of the matrix channel width. The relationship between the creep rupture life and the lattice misfit of γ/γ ’ , the coarsening of γ ’ precipitate and the precipitation of TCP phase are systematically discussed. In addition, according to the correlation between γ ’ phase evolution and creep characteristics during thermal exposure, a physical model is established to predict the remaining creep life.

The study aims to ascertain the influences of position on fracture toughness and fracture mechanism of inertial friction welded Ti-5Al-2Sn-2Zr-4Mo-4Cr joints. The room-temperature fracture toughness values of the parent material and three other regions in the weld were evaluated by standard crack tip opening displacement tests. The micro-structure and tensile properties of the welds were also investigated. Based on the observation of fracture surface and crack propagation path, a schematic illustration of the crack propagation was formed. The results suggest that the weld metal had the worst fracture toughness. The individual fracture toughness of different regions in the weld could be explained by the various modes of crack propagation, which were affected by different microstructures.

To avoid the formation of Ti-Ni intermetallics in a joint, three laser welding processes for Ti alloy–NiTi alloy joints were introduced. Sample A was formed while a laser acted at the Ti alloy–NiTi alloy interface, and the joint fractured along the weld centre line immediately after welding without filler metal. Sample B was formed while the laser acted on a Cu interlayer. The average tensile strength of sample B was 216 MPa. Sample C was formed while the laser acted 1.2 mm on the Ti alloy side. The one-pass welding process involved the creation of a joint with one fusion weld and one diffusion weld separated by the remaining unmelted Ti alloy. The mechanical performance of sample C was determined by the diffusion weld formed at the Ti alloy–NiTi alloy interface with a tensile strength of 256 MPa.

Grain refinement has a significant influence on the improvement of mechanical properties of magnesium alloys. In this study, a series of Al–Ti–C-xGd (x = 0, 1, 2, 3) master alloys as grain refiners were prepared by self-propagating high-temperature synthesis. The synthesis mechanism of the Al–Ti–C-xGd master alloy was analyzed. The effects of Al–Ti–C-xGd master alloys on the grain refinement and mechanical properties of AZ31 (Mg-3Al-1Zn-0.4Mn) magnesium alloys were investigated. The results show that the microstructure of the Al–Ti–C-xGd alloy contains α-Al, TiAl 3 , TiC and the core–shell structure TiAl 3 /Ti 2 Al 20 Gd. The refining effect of the prepared Al–Ti–C–Gd master alloy is obviously better than that of Al–Ti–C master alloy. The grain size of AZ31 magnesium alloy was reduced from 323 μm to 72 μm when adding 1 wt.% Al–Ti–C-2Gd master alloy. In the same condition, the ultimate tensile strength and elongation of as-cast alloy were increased from 130 MPa, 7.9% to 207 MPa, 16.6% respectively.

The effect of adding cerium on the microstructure and acid rain corrosion resistance of the AlSi11Cu3 alloy was investigated by means of optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The AlSi11Cu3 alloy was doped with varying stoichiometries of cerium to generate AlSi11Cu3- x Ce, where x = 0, 0.5, 1.0, and 1.5 wt.%. The results show that the α-Al, eutectic Si, and β-Al 5 FeSi phases in the AlSi11Cu3-1.0Ce alloy are significantly refined. Electrochemical tests demonstrated an increase in the self-corrosion potential value of the AlSi11Cu3-1.0Ce alloy from –670 mV to –628 mV relative to the untreated alloy. In addition, the AlSi11Cu3-1.0Ce alloy has the lowest corrosion current density (8.4 μA × cm –2 ). Immersion corrosion testing on the AlSi11Cu3-1.0Ce alloy revealed a corrosion rate of 0.71 mg × cm –2 × d –1 , constituting a 72% reduction in the corrosion rate compared to the untreated alloy. These results indicate that the AlSi11Cu3-1.0Ce alloy has a high resistance to acid rain corrosion, which is the result of a refinement of the cathode phases.

Titanium dioxide supports, which were prepared by roasting metatitanic acid under different conditions, were used to prepare a series of Ce–W–Ti catalysts. The structure and denitration properties of the catalyst were studied. The results showed that TiO 2 had different crystal types (mixed crystal phases with different proportions of anatase and rutile) under different roasting conditions, and the denitration efficiency of mixed crystal was better than that of pure phase TiO 2 . Ce–W/200 °C-1 hTiO 2 catalyst exhibited a prominent NO conversion rate, and it can reach higher than 90% at a temperature range from 250 to 500°C. The large specific surface area, low content of rutile TiO 2 in the support, high content of chemical adsorbed oxygen and high surface acidity were favorable to denitration performance of Ce–W–Ti catalyst.