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The effect of ultrasonic melt treatment (UST) on the solidification microstructure of an Al–5Ti–1B alloy containing high-volume fractions of Al3Ti and TiB2 particles is investigated for various UST times with different melt holding times. The as-cast Al–5Ti–1B alloy is composed of TiB2 and polygonal Al3Ti particles (present prior to UST), plate-like Al3Ti particles, and Al grains (formed during UST and/or solidification). The UST causes a size reduction and homogeneous distribution of the TiB2-agglomerated region containing many submicron-sized TiB2 particles pushed to the grain boundaries. The UST slightly decreases the size and improves the distribution of polygonal Al3Ti particles enriched in the TiB2-agglomerated region. Unlike the TiB2 and polygonal Al3Ti particles, which exhibit a minor refining effect, the plate-like Al3Ti particles show a significant refinement with UST application. The UST has a significant effect on the size distribution of Al grains by inducing the formation of medium-sized grains at the expense of small and large grains; however, it only has a slight effect on grain refinement. The degree of microstructure modification increases with increasing UST time but decreases with melt holding time after UST. The mechanisms for the refinement and dispersion of the TiB2 and Al3Ti particles and Al grains are discussed considering fragmentation, nucleation, and growth behaviors induced by the UST and subsequent solidification.

The correlation between primary Si and silicide refinement induced by ultrasonic treatment (UST) of multicomponent Al–Si alloy containing Ti, Zr, V, and P was investigated. UST significantly refined the primary Si phase owing to cavitation-induced wetting and deagglomeration of MgAl2O4 particles. Lowering the UST finish temperature caused deterioration of the degree of primary Si refinement, instead leading to silicide refinement. Cavitation-induced silicide nucleation on wetted MgAl2O4 consumed the MgAl2O4 particles, particularly in the case of primary Si nucleation. Similarly, the formation of an AlP phase on the silicide phase reduced the nucleation efficiency of the AlP phase. Poisoning of the MgAl2O4 and AlP phases by the silicide phase was responsible for the deterioration in primary Si refinement. Room-temperature tensile strength and high-temperature elongation were increased by UST and were dependent on the size of primary Si.

The effect of Cu/Mg solute combined with ultrasonic melt treatment (UST) on the microstructure and mechanical properties of a hypoeutectic Al-7Si alloy was investigated. Cu up to 4 wt pct and Mg to 1 wt pct were added to the alloy and UST was performed at about 100 °C above the liquidus temperature. UST at such a high temperature was ineffective in refining grain sizes but enhanced the microstructural homogeneity of the alloys with the refinement of α-Al secondary dendrite arm spacing (SDAS). It was found that both the grain size and the SDAS were solute sensitive: In the Al-7Si alloy with UST they insignificantly changed with Cu but decreased with an increase in Mg content. Along with the structural refinement, UST was likely to affect the solute redistribution and the subsequent formation of secondary phases (e.g., eutectic Si and Cu/Mg-rich intermetallic compounds (IMCs)). Quantitative analysis indicated that UST had significantly minimized microsegregation of Cu and Mg solutes, decreasing the amount of the IMCs finely and uniformly distributed. The underlying reason was attributed to the reduction in the size of the SDAS, which enabled the solid-state diffusion to occur more efficiently upon solidification. The most significant increase in the tensile properties was achieved for the Al-7Si-2Cu-1Mg alloy with UST where the SDAS was well refined and the grain size was the smallest among the alloys investigated. The important role of UST on the casting structure refinement and the solute distribution is discussed and the resulting mechanical properties are further explored.

Ultrasonic melt treatment (UST) was applied to an A390 hypereutectic Al–Si alloy in a temperature range of 750–800 °C and its influence on the solidification structure and the consequent increase in strength was investigated. UST at such a high temperature, which is about 100 °C above the liquidus temperature, had little effect on the grain refinement but enhanced the homogeneity of the microstructure with the uniform distribution of constituent phases (e.g. primary Si, α-Al and intermetallics) significantly refined. With the microstructural homogeneity, quantitative analysis confirmed that UST was found to suppress the formation of Cu-bearing phases, i.e., Q-Al5Cu2Mg8Si6, Al2Cu phases that form in the final stage of solidification while notably increasing the average Cu contents in the matrix from 1.29 to 2.06 wt%. A tensile test exhibits an increase in the yield strength of the as-cast alloy from 185 to 208 MPa, which is mainly associated with the solute increment within the matrix. The important role of UST in the microstructure evolution during solidification is discussed and the mechanism covering the microstructure-strengthening interrelationship of the ultrasonically treated A390 alloy is proposed.

The effects of ultrasonic melt treatment (UST) on the microstructure and mechanical properties of Al-12.2Si-3.3Cu-2.4Ni-0.8Mg-0.1Fe (wt%) piston alloy were systematically investigated. Rigid colonies consisting of primary Si, eutectic Si, Mg 2 Si and various aluminides (e-Al 3 Ni, δ-Al 3 CuNi, π-Al 8 FeMg 3 Si 6 , γ-Al 7 Cu 4 Ni, Q-Al 5 Cu 2 Mg 8 Si 6 and θ-Al 2 Cu) were observed in the as-cast alloys. The sizes of the secondary phases, eutectic cell and grain were significantly decreased by UST because of the enhanced nucleation of each phase under ultrasonic irradiation. The yield strength, tensile strength and elongation at 25 °C were significantly improved by UST mainly because of the refinement of the microstructures. Both tensile strength and elongation at 350 °C were also improved by UST despite the unchanged yield strength.

Aluminum matrix composites with a high volume fraction of B4C and TiB2 were fabricated by a novel processing technique - a quick spontaneous infiltration process. The process combines a pressureless infiltration with the combustion reaction of Al-Ti-B4C-CuO in molten aluminum. The process is realized in a simple and economical way in which the whole process is performed in air in a few minutes. To verify the rapidity of the process, the infiltration kinetics was calculated based on the Washburn equation in which melt flows into a porous skeleton. However, there was a noticeable deviation from the calculated results with the experimental results. Considering the cross-sections of the samples at different processing times, a new infiltration model (two step infiltration) consisting of macro-infiltration and micro-infiltration is suggested. The calculated kinetics results in light of the proposed model agree well with the experimental results.

Controlling the processing parameters is important to minimize such undesirable microstructural features in Al/TiC composites as unreacted C, incomplete reaction products of Al3Ti and TiC aggregates, which originate from the pellet microstructure upon the combustion reaction of an Al-Ti-C-CuO pellet in an Al melt. In particular, the mean particle size of elemental powders is a key factor linked to the formation of TiC aggregates, which is significantly suppressed with smaller initial particles of Ti and C by mixing them homogenously by ball milling. Al-Cu-Mg alloys reinforced with up to 12 vol pct TiC are fabricated by the developed process, followed by extrusion. The composites after heat treatment exhibit high elastic modulus and an ultimate tensile strength of 93 GPa and 461 MPa, respectively, with a low coefficient of thermal expansion of 17.11 ppm/K.

Soft magnetic materials play an important role in electronic energy components such as inverter and converter using transformer, inductors, etc.

Of various systems that utilize a self-propagating high-temperature synthesis, the Al-TiO2-C system is representative of in-situ production of metal matrix composites reinforced with TiC and Al2O3. Contrary to common understanding, however, the following reaction 4Al + 3TiO2 + 3C→3TiC + 2Al2O3 is infeasible in the Al-TiO2-C system with the given stoichiometric composition of 4Al + 3TiO2 + 3C. Experiments have shown that the formation of TiC and Al2O3 is feasible only in an Al-TiO2-C system that contains a certain amount of excess Al. In this study, the mechanism of the reactions in the Al-TiO2-C system was elucidated in order to explain why excess Al is needed to promote the formation of TiC and Al2O3. We also estimated the amount of excess Al that is necessary to promote the complete transformation of the Al-TiO2-C powders to TiC and Al2O3.

The effect of the Ti/B4C mole ratio on the fabrication behavior of Al composites is investigated using Al–Ti–B4C powder mixtures as reactants. The quick spontaneous infiltration (QSI) process combined with the combustion reaction and DTA analysis were used. According to the thermodynamic predictions, which are verified in the experimental results, TiB2 is formed in all the samples whereas TiC is only formed in reactants with a Ti/B4C mole ratio of more than two. The C atoms from the reacted B4C do not move into TiC but instead they move into Al3BC or Al4C3 when the Ti/B4C mole ratio is less than two. In addition, the reaction mechanism with a Ti/B4C mole ratio of 0.75 is investigated extensively.

Aluminum matrix composites with a high volume fraction of reinforcements are fabricated using a quick spontaneous infiltration process through a combustion reaction of an Al-Ti-B4C-CuO powder mixture in molten aluminum. A cold-compacted powder mixture in a cylindrical shape was used as a preform. The effects of the composition of the initial powder mixture on the sustaining of the compact shape were systematically examined and thereby an optimal composition for fabricating sound aluminum matrix composites was suggested. The compact shape was greatly affected by the initial composition of the powder mixture. A sufficiently high relative volume fraction of the solid particles in the compact is critical for sustaining the compact shape during the combustion reaction. The volume fraction of Al and Ti powders in the initial mixture affects whether crumbling of the compact occurs during the ignition delay time. This study can be beneficial to utilizing the Al-Ti-B4C system as to fabricate components with any desired shape.

Al matrix composites reinforced with TiC particles are fabricated by a thermally activated reaction of Al-Ti-C powder mixtures in an Al melt. In the presence of CuO, reactant mixtures in the form of a pellet added to molten Al at temperatures higher than 1093 K (820 °C) instantly reach the peak temperature over 1785 K (1512 °C), followed by combustion wave propagation with in situ synthesizing TiC with a size of approximately 1 μm. Incomplete reaction products such as unreacted C, Al3Ti, and TiC aggregates are also observed. The pellet microstructure evolution upon the combustion reaction indicates that preheating temperature, i.e., the initial melt temperature, affects both the thermodynamic and kinetic characteristics of the reaction, and thereby influences the final microstructure of the Al/TiC composites. Based on the experimental and theoretical results, a sequence of the reaction leading upto the in situ synthesis of TiC is illustrated and the corresponding mechanism for the present process is proposed.

The effect of ultrasonic melt treatment (UST) on the microstructure of hypereutectic Al-17 wt.% Si alloys was investigated. UST applied to a melt at a temperature range of 750 - 800 °C refines the primary Si dramatically but has little influence on the grain size of primary Al. The solidification behaviour was characterised by thermal analysis and a mechanism responsible for the primary Si refinement was suggested. Whilst UST has no effect on the grain refinement, a significant increase in the matrix hardness as well as the tensile strength in the as cast condition is possibly associated with solid solution hardening. Detailed microstructure analysis was carried out and characteristics of the intermetallic formation in the Al-17 wt.% Si alloys were further discussed in the view point of Cu solubility in the Al matrix, which is considered to increase with UST.

Particle distribution and hot workability of an in situ Al-TiCp composite were investigated. The composite was fabricated by an in situ casting method using the self-propagating high-temperature synthesis of an Al-Ti-C system. Hot-compression tests were carried out, and power dissipation maps were constructed using a dynamic material model. Small globular TiC particles were not themselves fractured, but the clustering and grain boundary segregation of the particles contributed to the cracking of the matrix by causing the debonding of matrix/particle interfaces and providing a crack propagation path. The efficiency of power dissipation increased with increasing temperature and strain rate, and the maximum efficiency was obtained at a temperature of 723 K (450 °C) and a strain rate of 1/s. The microstructural mechanism occurring in the maximum efficiency domain was dynamic recrystallization. The role of particles in the plastic flow and the microstructure evolution were discussed.

In situ Al/TiC composites with a homogeneous distribution of TiC reinforcements were prepared by adding a reactant mixture of Al-Ti-C to an Al melt. A certain amount of CuO addition facilitates a combustion reaction of the Al-Ti-C system and thereby enables the formation of in situ TiC at a reasonably low temperature range of 750–920 °C. Synthesised TiC particles with sizes of 1–2 μm are present in the Al matrix along with Al3Ti. Besides the CuO addition, the melt temperature plays a significant role in the final microstructure of the composites. Increase in the melt temperature up to 920 °C with CuO provides more external heat input and initiates the combustion reaction within a few seconds. Pellet microstructure evidently shows that the polygonal Al3Ti originates from the unreacted layer of which the distance is significantly shortens by increasing the melt temperature. The suppression of the Al3Ti formation is the most likely to occur at 920 °C, with producing a large volume fraction of TiC in situ synthesised.

A novel, quick, spontaneous infiltration process that combines with a combustion reaction from a powder mixture of Al–Ti–B4C–CuO is presented. The process is realized in a simple and economical way, with the whole process being performed in air in a few minutes. The microstructures of the composites exhibit quasi-continuous three-dimensional network structures composed of infiltrated aluminum and B4C particles surrounded by the aggregates of the reaction products. The composites exhibit a high elastic modulus with a low coefficient of thermal expansion.

The paper investigates the effect of the roll speed ratio on the deformation characteristics of interstitial free (IF) steel processed by the differential speed rolling (DSR) technique. An intense plastic strain induced by a single DSR with various roll speed ratios ranging from 1:1 to 1:4 for the lower and upper rolls was successfully imparted to the samples, resulting in the formation of fine elongated ferrite grains as the roll speed ratio increased. Observations of the preferred orientation using electron back-scattered diffraction and transmission electron microscopy revealed that the {110} slip was readily activated as the dominant deformation mode in order to accommodate the intense plastic strain imposed by the DSR. In addition, the microhardness values of the IF steel sample deformed via DSR under a roll speed ratio of 1:4 increased, and this is discussed on basis of the frictional force between the roll and the sample during DSR deformation.

Microstructures and wear properties of a newly developed Al–Mg–Si–CoNi alloy by the addition of ball-milled CoNi powders have been investigated. The ball-milled CoNi powder reacted with aluminum to form a ternary Al4(Ni,Co)3 phase in the microstructure and the phase retained its crystal structure until T6 treatment. The wear properties of the Al–Mg–Si–CoNi alloy have been compared to a commercial A6061 (Al–Mg–Si) alloy under dry sliding conditions. The wear test was conducted under a frequency of 4 Hz and a load range of 50–300 N. The Al–Mg–Si–CoNi alloy exhibited better wear properties than the A6061 alloy for all test conditions in this investigation. On the basis of the observation and analysis of the worn surface, worn subsurface and wear debris, the wear mechanism acting on each load has been evaluated for an Al–Mg–Si–CoNi alloy and an A6061 alloy.

The formation of black ceramic layer produced by plasma electrolytic oxidation (PEO) coating has been investigated as a function of coating time. A series of PEO coatings was carried out on aluminum alloy sample in a phosphate electrolyte containing sodium tungstate (Na2WO4) with four different coating times, i.e., 20, 100, 200 and 300 s. As the coating time increased, the amount of tungsten element in the ceramic layer increased, resulting in the black ceramic layer. This phenomenon was discussed based on the electrochemical reaction assisted by micro sparks to form WO3 compounds in the ceramic oxide layer. [doi:10.2320/matertrans.M2011263]

The fracture property improvement of Ni-Mn-Ga-Fe ferromagnetic shape memory alloys containing ductile γ particles was explained by direct observation of microfracture processes using an in-situ loading stage installed inside a scanning electron microscope (SEM) chamber. The Ni-Mn-Ga-Fe alloys contained a considerable amount of γ particles in β grains after the homogenization treatment at 1073 K to 1373 K (800 °C to 1100 °C). With increasing homogenization temperature, γ particles were coarsened and distributed homogeneously along β grain boundaries as well as inside β grains. According to the in-situ microfracture observation, γ particles effectively acted as blocking sites of crack propagation and provided the stable crack growth, which could be confirmed by the R-curve analysis. The increase in fracture resistance with increasing crack length improved overall fracture properties of the Ni-Mn-Ga-Fe alloys. This improvement could be explained by mechanisms of blocking of crack propagation and crack blunting and bridging.

The effects of terbium addition on the microstructures and properties of polycrystalline Ni48.8Mn29.7Ga21.5 alloy (numbers indicate at.%) were investigated. The results show that the grain size of Ni-Mn-Ga alloy decreases significantly with the addition of Tb, and Tb elements are found to exist in the grain boundary region and form a (Ni, Tb)-rich quaternary phase. The compressive ductility and fracture toughness increased with the addition of Tb. The improvement of mechanical properties and the slight change of martensitic transformation temperature and the magnetic properties of the Tb-added alloys are discussed in terms of the modification of microstructures with the addition of Tb.

Nanostructured Ti-Ni alloys were prepared by cold working followed by annealing, and then their shape memory characteristics and superelasticity were investigated by means of differential scanning calorimetry (DSC), transmission electron microscopy (TEM), thermal cycling tests under constant load and tensile tests. Morphology of amorphous phases induced by cold working depended largely on the amount of cold working. They had domain like shape in the 40% cold rolled alloy, while had mainly wide band shape in the 70% cold rolled alloy. In 40% cold rolled alloy, the average grain size increased from 27 nm to 80 nm with increasing annealing temperature from 573 K to 673 K. Transformation elongation increases with raising annealing temperature, which was ascribed to the increase in grain size reducing the constraints of grain boundaries. Transformation hysteresis increased rapidly with raising annealing temperature up to 623 K, above which they almost keep constant, which was ascribed to the small grain size and large constraints of grain boundaries.

Thick alumina coatings were performed on A356/20 vol.% SiCp composites by micro-arc oxidation (MAO) process with different processing time. MAO-coated layer is composed of α-alumina, γ-alumina and mullite, and the hardness value increases and then decreases sharply with distance from the interface. The dry sliding wear tests were performed on A356/20 vol.% SiCp composites with and without surface coating. The samples were tested by pin-on-disc wear test equipment with different applied load and sliding velocity in a temperature range 25–180 °C. On the basis of the observations and analysis of the worn surface, worn subsurface, wear debris and variation of friction coefficient, the role of MAO coating layer is examined. It is revealed that MAO coating improves resistance to wear of A356/20 vol.% SiCp composites. The coated and uncoated specimens show similar results in wear rate for the mild wear regions, whereas the coated specimen show much better resistance to wear in the severe wear conditions for A356/SiCp composites by retarding the transition of the mild-severe wear of the materials.

Thick alumina coatings were performed on A356-20vol.% SiCp composites by micro-arc oxidation (MAO) process with different processing time. The dry sliding wear tests were performed on A356-20vol.% SiCp composites with and without surface coating. The samples were tested by pin-on-disc wear test equipment with different applied load and sliding velocity. It is revealed that MAO coating improves resistance to wear of A356-20vol.% SiCp composites in the severe wear conditions. On the basis of the observations and analysis of the worn surface, worn subsurface, wear debris and variation of friction coefficient, the role of MAO coating layer is examined.

Deformation behavior of temperature gradient anneal(TGA) treated Ti-50.0Ni(at%) alloys were investigated by means of thermal cycling tests under constant load and tensile tests. TGA treated Ti-Ni alloy wires showed a sequential deformation behavior along the length of the specimen since the stress required for the B2-B19’ transformation increased with decreasing annealing temperature. Considerably large residual elongation(about 0.4 %) occurred in the TGA treated Ti-Ni alloy under the applied stress of 80 MPa, which is ascribed to the fact that yield stress of the sample annealed at 823 K is lower than the stress required for the B2-B19’ transformation of the sample annealed at 658 K.

Micro-formability of U groove on Zr 62 Cu 17 Ni 13 Al 8 (numbers indicate at.%) bulk metallic glass plate was investigated by varying the process parameters, such as time, load and temperature. Micro-stamping machine and Si micro-dies with U groove were employed for micro-forming test. Micro-formability was estimated by comparing R f . values (=A f /Ag), where Ag is cross-sectional area of U groove, and A f - the filled area by micro-formed sample. The R f values increased with increasing load, time and temperature in the supercooled liquid state of Zr 62 Cu 17 Ni 13 Al 8 bulk metallic glass. Micro-formed U patterns showed smooth surface with no defects like surface crack. Maximum R f value was about 0.5 for the specimen micro-formed at 420 °C, at 167 N load for 25 min. It was concluded that the patterns with aspect ratio = 1 can be micro-formed at the process condition given above.

TiNi shape memory alloy (SMA) thin sheets with a thickness of 120 μm were fabricated by the method of bonding and cold rolling and subsequent heat treatment of elemental Ti and Ni foils. The annealing temperature and time have been investigated with regard to their effects on the phase composites and microstructures of the as-roll-bonded Ti/Ni multilayers. It is found that the TiNi phase which shows shape memory effect is easily to be synthesized by the subsequent heat treatment even though it was preformed by annealing at a relatively low temperature of 650 °C and for a short time of 6 h. The shape memory effect has been examined by DSC for the fabricated TiNi thin sheets and it reveals a good martensitic and reverse transformation behavior from B2 to B19′ of M s at around 60 °C and transition hysteresis of about 30 °C. A tensile test at the temperature above A f revealed that recovery strains of average 1.5% in superelasticity has been obtained for the TiNi thin sheets.

The concept of micro-contact in electrodes was incorporated into AC two-probe impedance spectroscopy in order to clarify the electrode-related responses in solid oxide fuel cells (SOFCs). The pointed contact of one electrode was combined with the planar electrode as a counterpart in characterizing an YSZ (yttria-stabilized zirconia)/Pt interface of SOFCs. The micro-contact in electrodes induced the decrease in capacitance and the increase in impedance and amplified the bulk responses in YSZ due to the constricted electroding area. The bulk-related portions can be separated from the interfacial polarization of Pt, even though the electrolyte/electrode interface was found to be very sensitive to the measurement condition, i.e., the oscillating voltage. The resolved bulk and interfacial resistances were analyzed using a concept of “spreading resistance.’’ Furthermore, the electrode-related issues were ramified for the application of impedance spectroscopy to the solid oxide fuel cells.

Thick and hard ceramic coatings were fabricated on A356 aluminum alloy by using plasma electrolytic oxidation (PEO) technique. The microstructure and phase composition of the PEO coatings were examined by using SEM and XRD method. It is found that the PEO coatings are mainly composed of crystalline α-Al2O3 and mullite. The dry sliding wear test of PEO coatings were carried out on a ring-on-ring wear machine. Results shows that there is hardly no wear loss of polished PEO coatings while the wear rate of uncoated aluminum alloy is 4.3 × 10−5 mm3.(N.m)−1 at a speed of 0.52 m.s−1 and a load of 40 N.

LSGM is known to have a critical limit in terms of its application due to its chemical reactivity with other unit cell components. In particular, the formation of a highly resistive La–Sr–Ga–O phase at the interface of the anode and electrolyte poses a major obstacle toward the application of LSGM-based SOFCs. In this study, we investigated the interfacial reactions in LSGM-based SOFCs under various fabrication conditions in order to identify a means of avoiding or diminishing undesirable interfacial reactions. The electrical properties and phase composition of all reaction products were analyzed with the DC 4-point probes technique and X-ray diffraction. Microstructural evolution due to the chemical reactions between unit cell components was characterized with Environmental Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy. According to the analysis of the interfacial reaction, a serious reaction zone exists, critically increasing the internal ohmic resistance of the cells. Moreover, this interfacial reaction decreases the OCV (open cell voltage) and consequently deteriorates the unit cell performance. Possible approaches to solving this reaction problem are reducing the heat-treatment temperature or introducing an effective buffering layer to prohibit interfacial reaction.

The preparation of TiNi SMA thin strip via cold roll-bonding and subsequent annealing treatment of pure Ti/Ni multilayer has been studied. The relationships between processing variables and microstructure formed based on the proposed method have been investigated by OM, SEM/EDS and XRD detections. It shows that the Ti/Ni multilayer with reduction of 97% can be possibly obtained by cold rolling of initially hot-press bonded pure Ti and Ni foils. Within the high thickness reduction of the multilayer, the TiNi phase is easily formed at relatively low annealing temperature and short annealing time. DSC measurement for the prepared TiNi strip have shown a good B2 to B19′ transformation behaviour and Ms at around 60 °C, transition hysteresis of about 30 °C and transition enthalpy of average 24 J/g, which is similar to those by the conventional ingot-metallurgy method.

In this investigation, Fe/Ag and Ni/Ag multilayers were fabricated by a bonding and rolling method. The hard phase of the multilayer, such as Ni and Fe, necks, elongates and finally ruptures with increasing thickness reduction. The morphological features of the layer with thickness reduction were different with initial thickness ratio. The changes of the microstructures for Fe/Ag and Ni/Ag multilayers were examined on the basis of the plastic instability criteria for diffused necking. The critical reduction for necking of the hard constituent phase of the layer is dependent on the flow properties of the phases such as strength coefficient and strain hardening exponent, and the initial thickness ratio of the constituent phases.

The electrical conductivity and phase stability of ZrO 2 co-doped with Sc 2 O 3 and CeO 2 were investigated in order to search for a better solid electrolyte material, which can be applicable for intermediate- or low-temperature solid oxide fuel cells (SOFCs). Present study showed that ZrO 2 doped with Sc 2 O 3 and CeO 2 did not show any phase transition during heat treatment up to 1250–1550 °C and was exceedingly stable as a cubic phase in all temperature ranges. The ZrO 2 co-doped with Sc 2 O 3 and CeO 2 showed much higher electrical conductivity than YSZ in the whole temperature range of 300–1100 °C and better long-term stability than any other Sc-ZrO 2 -based electrolyte. From the long-term performance check of the 5×5 cm 2 unit cell operation, we could verify that ZrO 2 co-doped with Sc 2 O 3 and CeO 2 can be a strong candidate electrolyte material for intermediate- or low-temperature SOFC.

We developed an innovative processing technology, liquid condensation process (LCP) to produce thin and large size anode substrate with very high uniformity which allowed easy manipulation of the microstructure and/or pore structure of anode substrate. The anode substrate made with LCP had very homogeneous microstructure, which would be helpful to induce homogenous physico-chemical properties of the anode substrate. Microstructure of anode substrate was critically evaluated in terms of pore structure development by varying compaction pressure. According to electrical and microstructural characterizations of the anode substrate, the physico-chemical properties of the anode substrate including gas permeability and electrical conductivity were closely related with the microstructure and/or pore structure of anode substrate. Proper method to manipulate the processing variables to control the microstructure of anode substrate to achieve superior performance of solid oxide fuel cell was discussed.

Several kinds of powders and aluminum alloys are adopted to study the feasibility of the fabrication of aluminum matrix composites through plasma synthesis. Some powders do not incorporate into the molten aluminum due to reflection on the melt surface and dissolution in the plasma arc. On the contrary, iron powders are well incorporated into the molten aluminum. The iron powders incorporated into the molten aluminum make angular Al13Fe4 intermetallic compounds in the matrix. In addition, some portion of iron powders dissolve into the matrix and change the microstructures of the matrix alloys. The effects of dissolved Fe on the microstructures and mechanical properties of the composites are examined.

The present work was undertaken to highlight a novel in-situ process in which plasma spraying techniques plus electromagnetic stirring were used to produce Al/Al 3 Fe composites consist of angular and needle-like morphology of Al 3 Fe intermetallic compounds of about 10–20 μm in size. The microstructures of fabricated materials consisted of α-Al and Al 3 Fe intermetallic compounds, and the size, volume fraction and shape of Al 3 Fe intermetallic compounds depended mainly on the temperature of the melt and the plasma spraying conditions such as input current, gas flow rate of plasma and spraying distance. The microstructural difference arose from the difference of instantaneous temperature and velocity of the iron particle on the melt surface. The temperature and velocity of the iron particles in the plasma arc were calculated and the results were compared with the fabricated microstructures. In addition, the evolution of microstructures of angular and needle-like Al 3 Fe intermetallic compounds was analyzed morphologically by spherical shell model incorporating of diffusion kinetics.

The evolution of intermetallic compounds for Al/Fe in situ composites fabricated by the plasma synthesis method (PSM) was investigated through the microstructural analyses for the partially reacted particle region. The partially reacted particle is composed of Al/Al 13 Fe 4 /Al 5 Fe 2 /Fe layer. Based on the concept of effective free energy of formation, the first phase that nucleates on the interfacial layer of Al/Fe is determined as Al 13 Fe 4 . By the reaction of Al 13 Fe 4 and Fe, Al 5 Fe 2 forms and grows inward. Due to heat extraction by the reaction, the edge of Al 13 Fe 4 dissolves to form angular Al 13 Fe 4 in the matrix. By the reaction and decomposition of Al/Fe through the intermediate phase of Al 5 Fe 2 , the Fe particles transform to Al 13 Fe 4 in the plasma synthesis method. In addition, the differences of main intermetallic compounds between by the hot dipping process and by the plasma synthesis method were discussed.

Aluminum based metal–metal composites were fabricated by the plasma synthesis method with Fe, Cr and Ni powders. The fabricated microstructures are mainly composed of α-Al and aluminide intermetallic compounds. However, the microstructural features are different with each powder. The as-cast microstructures were analyzed by the properties of powders such as temperature in the plasma arc, diffusivity and solubility in the molten aluminum.

Keyword: Gold bonding wire, Grain Boundary, Misorientation, EBSD Abstract. Cold drawn gold bonding wires have been investigated with Electron Back Scatter Diffraction (EBSD). The textures of drawn gold wires contain major , minor and small fractions of complex fiber components. The oriented regions are located in the center and surface of the wire, and the complex fiber component regions are located near the surface. The oriented regions occur throughout the wire and have large Taylor factors and would be expected to have higher stored energy as a result of plastic deformation compared to the regions. Large misorientations (angles > 40 °) are located between the and regions, which means that the boundaries between them are likely to have high mobility. Boundaries within the regions are predominantly tilt grain boundaries with large misorientations, similarly, the regions have tilt grain boundaries with smaller misorientations. It appears that the stored energy as indicated by geometrically necessary dislocation content in the subgrain structure is similar in all orientations despite the large differences in Taylor factor.

The MMCs of Al/Al 3 Fe and A2218/Al 3 Fe composites were fabricated by injection of Fe particles into the Al melt through a plasma synthesis method. The elastic modulus and yield strength of the fabricated composites were evaluated through the measurement of ultrasonic velocity and room temperature compression test. The measured values were compared with the predicted ones based on the continuum mechanics approach for the elastic modulus and the micromechanics approach for the yield strength. The properties of Al/Al 3 Fe were well consistent with the predicted models, while the properties of A2218/Al 3 Fe exhibited lower values than the predicted ones. The deviations of the properties for A2218/Al 3 Fe were examined in terms of the matrix microstructures.

The wear behavior of an A2218 alloy and an A2218/Al3Fe composite fabricated by the plasma synthesis method was investigated under dry sliding conditions. The wear tests were carried out at a sliding speed of 0.2 m/s and at the load range of 3–600 N. The variation of wear rate with applied load is composed of two regions for both materials and the two regions belong to mild wear. On the basis of observation and analysis on the worn surface, subsurface and the wear debris, the wear mechanism acting on each region was identified. At low loads, oxidative wear is the main wear mechanism and at high loads, the wear is controlled mainly by delamination and adhesive wear mechanism and oxidative wear is an additional wear mechanism. The A2218/Al3Fe composite exhibits an improved wear resistance at lower loads. On the contrary, at higher loads, due to the presence of the mechanical mixed layer on the worn surface of the A2218 monolithic alloy, both the monolithic alloy and composite exhibit similar wear rate.

The electrical property and defect structure of 12 mro CeO –ZrO , which has been known for good mechanical and 22 thermal properties, were studied in order to investigate the possibility of its use as a solid electrolyte for electrochemicaldevice, like electrolyser, sensor and fuel cell. The electrical conductivity of 12 mro CeO –ZrO was greatly enhanced and 22 electrolytic domain boundary EDB was also extended to lowŽ. P with yttria doping, which were readily comparable with O 2 those of commercial electrolyte, YSZ, CSZ. Unlike normal stabilized zirconia, saturation point of electrical conductivityappeared at higher doping concentration 12–15 mŽ.ro yttria and the activation energy was not also changed seriously withdoping till 15 mro yttria doping. q2001 Elsevier Science B.V. All rights reserved. Keywords: Zirconia; Ceria; Yttria; Electrical conductivity; Defect structure 1. IntroductionIn the last few decades, zirconia-based ceramichas been studied with great interests for many appli-cation fields due to its good mechanical, chemicaland electrolytic properties. Especially, doped zirco-nia with a lower valence cation like Ca

Dry sliding wear behavior of spray deposited Al–6Cu–Mn/13 vol.% SiCp composites in both as-sprayed and forged states has been studied. Wear mechanisms in different wear regions and the influence of porosity on wear behavior are discussed. Within the applied load range of 5–400 N (corresponding normal stress is 0.1–8 MPa), the variation of wear rate with applied load in the as-sprayed composite can be divided into three wear regions, while the as-forged composite four wear regions. A transition load from mild to severe wear could be observed with increasing load. Severe wear was controlled by adhesion mechanism. Mild wear was associated with three different mechanisms: oxidation, delamination and subsurface-cracking assisted adhesion wear. The wear resistance of the as-sprayed composite was similar to that of the as-forged composite at lower loads. However, at higher loads, the as-sprayed composite had a higher wear rate and small transition load, therefore, exhibited inferior wear resistance than the as-forged composite. At lower loads, pores beneath the worn surface of the as-sprayed composite were stable and could not propagate significantly. Therefore, porosity displayed a very small influence on dry sliding wear behavior of the composite. At higher loads, the pores beneath the worn surface became unstable and the cracks originated from these pores could propagate during wear process, resulting in a higher wear rate and smaller transition load.

The dry sliding wear of spray deposited Al–6Cu–Mn alloy was studied as a function of applied load in the range of 5–400 N. The variation of wear rate with applied load was obtained, from which four regions can be observed. On the basis of observations and analyses on the worn surface, the worn subsurface, the wear debris and friction coefficient, wear mechanism in different regions has been identified. Two wear regimes, i.e. mild and severe wear, were displayed in the entire applied load range. The transition from mild to severe wear occurred at a critical load. Mild wear involves three regions in the wear rate vs. load variation, and the wear in each region was controlled by different wear mechanism. With increasing load, the dominant wear mechanism in the period of mild wear displays successively oxidative wear, delamination and subsurface-cracking assisted adhesive wear. Severe wear was operated by the adhesive wear mechanism and the wear debris was formed by the shear fracture of subsurface material of the pin. The transition from mild to severe wear depended on the strength of the material of the pin adjacent to the contact surface and the strain-induced shear stress created by applied load.

The present investigation was carried out to provide a deeper insight into the mechanism of wear behavior of A356-15 vol pct SiCp composite under controlled argon and oxygen atmospheres through a detailed characterization of worn surfaces and subsurfaces. Dry sliding wear tests were performed for both as-cast and T6-treated specimens using a pin-on-disc machine with three sliding velocities (0.5, 1, and 2 ms−1) and three loads (1, 2, and 3 MPa). The wear rate of A356-15 vol pct SiCp composite was lower by nearly one order of magnitude under argon atmosphere compared to the specimens tested under oxygen atmosphere for all experimental conditions. Under argon atmosphere, the mechanism of material removal was by delamination wear and did not change within the parametric regime. In the case of the specimen tested under oxygen atmosphere, the wear behavior of the composite depended on the experimental conditions. At low load and low sliding velocity, the material removal was by abrasion. While at high load and high sliding velocity, the material removal mechanism was by delamination wear. Further, the mechanical mixed layer (MML) formed under argon atmosphere was more stable and homogenous compared to that formed under oxygen atmosphere. The MML formed under both atmospheres revealed much less in Fe content.

The awareness of symptoms of global warming and its seriousness urges the development of technologies to reduce greenhouse gas emissions. Carbon dioxide (CO(2)) is a representative greenhouse gas, and numerous methods to capture and storage CO(2) have been considered. Recently, the technology to remove high-temperature CO(2) by sorption has received lots of attention. In this study, hydrotalcite, which has been known to have CO(2) sorption capability at high temperature, was impregnated with K(2)CO(3) to enhance CO(2) sorption uptake, and the mechanism of CO(2) sorption enhancement on K(2)CO(3)-promoted hydrotalcite was investigated. Thermogravimetric analysis was used to measure equilibrium CO(2) sorption uptake and to estimate CO(2) sorption kinetics. The analyses based on N(2) gas physisorption, X-ray diffractometry, Fourier transform infrared spectrometry, Raman spectrometry, transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy were carried out to elucidate the characteristics of sorbents and the mechanism of enhanced CO(2) sorption. The equilibrium CO(2) sorption uptake on hydrotalcite could be increased up to 10 times by impregnation with K(2)CO(3), and there was an optimal amount of K(2)CO(3) for a maximum equilibrium CO(2) sorption uptake. In the K(2)CO(3)-promoted hydrotalcite, K(2)CO(3) was incorporated without changing the structure of hydrotalcite and it was thermally stabilized, resulting in the enhanced equilibrium CO(2) sorption uptake and fast CO(2) sorption kinetics.