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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.

This work probes the effect of ultrasonic melt treatment (UST) on primary intermetallic particles and α-Al using pure Al and Al–Zr alloys (Al–0.3Zr–0.1Ti, Al–0.5Zr, Al–0.5Zr–0.5Mg–0.9Si) solidified at various cooling rates of 0.2–70 K s−1. The application of UST is shown to decrease the size and increase the number density and volume fraction of D023-structured primary Al3Zr and Al3(Zr,Ti) particles with a high nucleation potency for α-Al formation. High-resolution transmission electron microscopy analysis reveals that the cavitation-induced wetting and dispersion of γ-Al2O3 inoculant particles contribute to the refinement of primary intermetallic particles. The grain size of Al–Zr alloys increases with increasing cooling rate because of the concomitantly reduced formation of primary intermetallic inoculant particles. The UST-induced refinement of primary Al3Zr particles and the increased number density lead to grain refinement in Ti-free Al–Zr alloys. For the Ti-containing Al–Zr alloy, UST-induced grain refinement is achieved only at a very low cooling rate of 0.2 K s−1, possibly because of the side effects of UST on the growth-restricting influence of Ti. The fast cooling–induced solidification enables significant age-hardening by L12-Al3Zr nanoprecipitation (~5 nm) and is not affected by UST. Thus, this study shows that UST can be used to reduce the degree of grain coarsening of age-hardenable Al–Zr alloys at high cooling rates.

Ultrasonic melt treatment (UST) is known for refining microstructures including intermetallic compound (IMC)s, and it is expected that the microstructural benefits induced by UST may reduce the tim...

In this study, microstructural evolution during solidification of a hypereutectic Al&ndash, Mn&ndash, Fe&ndash, Si alloy was investigated using semi-quantitative two-/three-dimensional phase-field modeling. The formation of facetted Al6Mn precipitates and the temperature evolution during solidification were simulated and experimentally validated. The temperature evolution obtained from the phase-field simulation, which was balanced between extracted heat and latent heat release, was compared to the thermal profile of the specimen measured during casting to validate the semi-quantitative phase-field simulation. The casting microstructure, grain morphology, and solute distribution of the specimen were analyzed using electron backscatter diffraction and energy-dispersive spectroscopy and compared with the simulated microstructure. The simulation results identified the different Fe to Mn ratios in Al6(Mnx,Fe1&minus, x) precipitates that formed during different solidification stages and were confirmed by energy-dispersive spectroscopy. The precipitates formed in the late solidification stage were more enriched with Fe than the primary precipitate due to solute segregation in the interdendritic channel. The semi-quantitative model facilitated a direct comparison between the simulation and experimental observations.

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.

This paper shows that the addition of transition elements significantly influences the microstructure and tensile properties of Al–12Si alloy cast under ultrasonic melt treatment (UST). The alloys contained primary Si, eutectic Si and a variety of intermetallic compounds (IMCs); the addition of Mn and Ni changed the solidification sequence by forming primary α-Al15(Fe,Mn)4Si2 and e-Al3Ni prior to primary Si formation. The primary Si and primary IMCs competitively consumed the nucleation sites introduced by UST, thereby influencing their refining efficiencies; the efficiency of primary Si refinement by UST increased with increasing the fraction of primary Si formed prior to IMC formation, whereas it deteriorated with increasing primary IMC fraction. The refining efficiency of eutectic Si and eutectic IMCs was not affected by the type and fraction of the primary phase. Using a Ti sonotrode for UST caused Ti contamination, resulting in grain refinement by forming Ti(Al,Si)3 particles and increasing the amount of Ti solutes. Regardless of transition elements content, the application of UST improved the tensile strength at 25 °C and 350 °C. The refinement of IMCs caused by UST allowed the alloy to contain more IMCs without deterioration of room-temperature tensile strength. This enhanced the increment of high-temperature tensile strength by IMCs. Ductility of heavily alloyed systems was also improved by UST.

The effects of ultrasonic melt treatment (UST) and solution treatment on the microstructure and mechanical properties of a low-density multicomponent Al70Mg10Si10Cu5Zn5 alloy at room and elevated temperatures were investigated. The as-cast Al70Mg10Si10Cu5Zn5 alloy was composed of an fcc Al solid-solution, coarse secondary phases (5–30 μm), fine Cu-containing precipitates (

The effects of ultrasonic melt treatment (UST) on the microstructure and tensile properties of three multicomponent Al Si alloys with different Si contents (12, 15, and 18 wt%Si) and solution treatments were systematically investigated at room and elevated (350 °C) temperatures. The microstructures of these alloys consisted of primary Si, eutectic Si, Mg2Si, and various types of aluminides, but the average size and area fraction of the primary Si increased with Si content. The application of UST caused a transformation from dendritic to equiaxed cells and a reduction in grain size, with a significant reduction in the size of all secondary phases (i.e., Si, Mg2Si and aluminides). Both the strength and ductility at room and elevated temperatures were greatly improved by UST, mainly due to microstructure refinement. Improvements in the high-temperature tensile strength as a result of UST increased with increasing Si contents, due to the enhanced refinement of primary Si by UST with increasing Si contents. The spherodization of rigid phases induced by solution treatment can improve the strength and ductility at room temperature, but can also cause a loss of strength at elevated temperatures due to the relaxation of the interconnected network structure of rigid phases caused by their spherodization.

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.

Al–xMg–10Si–10Cu–10Zn (in wt%) alloy is fabricated with a high volume fraction of coarse multi-phase particles in the aluminum matrix. Permanent mold casting is carried out with a selective ultrasonic melt-treatment for 60 s at 1000 K. A step mold is used to achieve three different cooling rates. Blocky primary Mg2Si particles are homogeneously distributed through the Al matrix and eutectic phases such as Si, Q–Al5Cu2Mg8Si6, and θ-Al2Cu are found in the dendritic boundaries. Ultrasonication significantly decreases the porosity and the size of microstructural constituents such as primary Mg2Si phases. Refinement of primary Mg2Si by ultrasonication is more effective in the specimens with higher cooling rates. The compressive properties at room temperature and 623 K are enhanced in the ultrasonicated alloys. By heat treatment at 713 K, very fine θ′ precipitates with size less than 10 nm are formed through the Al matrix and blocky Mg2Si and Q phases were spheroidized.

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.

In this study, an AlMg8Si9Cu10Zn10 (in wt%) alloy is fabricated with a high volume fraction of coarse secondary phases, which is higher fraction than in the conventional piston alloys. Ingots are cast in a permanent mold after an ultrasonic melt treatment for 60 s at the temperature range of 750–700 °C. Microstructure of AlMgSiCuZn alloy consists of Si, Zn, Mg2Si, Q-Al5Cu2Mg8Si6, and θ-Al2Cu phases. By the heat-treatment at 440 °C, Q-phase at the vicinity of blocky Mg2Si phase grows and the roundness of the second phases increases with respect to the heat-treating time. Compared with the as-cast specimen, room-temperature ultimate compressive strength of the heat-treated specimens increases. However, maximum compressive stress at 350 °C is slightly decreased by heat treatment. The formation of fine clusters increases the ultimate compressive strength, while the spheroidization of bulky secondary phases during heat treatment deteriorates the ultimate compressive strengths.

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.

Hot working behavior of an aluminum alloy matrix composite reinforced with TiC particulates was investigated by a high temperature compression test. Power dissipation maps were constructed using a dynamic material model and the deformation mechanism was investigated by means of an EBSD analysis. The interrelationship between the microstructure evolution and the efficiency of power dissipation was derived and the roles of TiC particles and other constituent phases in determining processing maps were further discussed.

A feasible way to fabricate in-situ Al/TiC composites was investigated. An elemental mixture of Al-TiO2-C pellet was directly added into an Al melt at 800-920°C to form TiC by self-combustion reaction. The addition of CuO initiates the self-combustion reaction to form TiC in 1-2 μm at the melt temperature above 850°C. Besides the CuO addition, a diluent element of excess Al plays a significant role in the TiC formation by forming a precursor phase, Al3Ti. Processing parameters such as CuO content, the amount of excess Al and the melt temperature, have affected the combustion reaction and formation of TiC, and their influences on the microstructures of in-situ Al/TiC composites are examined. (Received March 15, 2012)

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.

A356/45vol.%SiCp composites with a uniform distribution of SiC particles have been fabricated by a liquid pressing method. Increasing the melt temperature, holding time and pre-treatment of SiCp by thermal oxidation improves the soundness of composites for the liquid pressing method. The sound composites exhibited low coefficient of thermal expansion (8 ppm/K) and high thermal conductivity (155 W/m K). The measured values for coefficient of thermal expansion agree well with the predicted values based on Turner’s model irrespective of porosity. The measured values for thermal conductivity decrease with porosity, and the effect of pore on the thermal conductivity has been evaluated based on the modified Hasselman–Johnson model.

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.

Ni sulfides layers were formed on the surface of a Ti 50 Ni 50 alloy by reacting sulfur with a Ni film deposited on the alloy, and then microstructures, transformation behavior, shape memory characteristics, superelasticity and electrochemical properties were investigated. When a Ni film deposited on a Ti 50 Ni 50 alloy was annealed under the sulfur pressure of 100 kPa at 623 K, sulfides layers consisted of NiS and NiS 2 were formed. When annealing was made at 648 K with annealing time less than 0.9 ks, sulfides layers with a mixture of NiS and NiS 2 were formed, while only NiS 2 was formed when it was made for 1.8 ks. When annealing was made at 673 K with annealing time longer than 0.9 ks, only NiS 2 was formed. With raising annealing temperature and prolong annealing time, NiS changed into NiS 2 accompanied with a morphological change from a particulate-like to a dense film-like. A Ti 50 Ni 50 alloy with surface NiS 2 layer showed the two-stage B2-R-B19' transformation behavior, the shape memory effect and a partial superelasticity with a superelastic recovery ratio of 78%. NiS 2 cathode showed a clear discharge behavior with multi-voltage plateaus induced by intermediate reaction products; NiS and Ni 3 S 2 . The initial discharge capacity was 743 mA h g ―1 corresponding to 85% of theoretical capacity and 65% of capacity duration is obtained at 20th discharge.

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.

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.

According to the characterization of the microstructure and properties of solid oxide fuel cells (SOFC) electrodes, it is essential to verify various processing variables to control microstructural parameters, such as particle size, composition and spatial distribution of the constituent phases of the electrode in order to reduce the ohmic and diffusional polarization losses of the unit-cell performance. From this viewpoint, a current-collecting layer with controlled microstructure very effectively enhances the unit-cell performance by reducing the ohmic and polarization resistance of the cathode. The maximum power density of a 5 cm × 5 cm unit-cell with the controlled current-collecting layer is ∼1.5 W cm −2 at 750 °C, while a unit-cell without the layer is much lower, viz., 0.9 W cm −2 .

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.

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.

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 microstructural changes were investigated in an Al-Cu-Mn alloy reinforced with SiC particles after being kept in the liquid or semi-solid state. The microstructural and compositional changes were characterized by differential thermal analysis (DTA), X-ray diffraction, and scanning electron microscopy (SEM) equipped with an energy dispersive X-ray analysis (EDXA) system. The solidification behavior of the monolithic alloy is followed by the Al-Cu-Mn ternary system while its composites showed the Al-Cu-Mn-Si quaternary system due to the rejection of Si from SiC particles after being kept in the liquid or semi-solid state. SiC particles were attacked heavily and a large amount of reaction product, Al 4 C 3 was formed. The extent of reaction was calculated from the contents of Si in matrix by the DTA method for determining the liquidus. The result was compared with the quantitative metallography.