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Three solid phases are involved in the phase equilibria of the important intermetallic compound Ni₃Al near its melting point, β, γ` (Ni₃Al) and γ. The generally-accepted phase diagram involves a eutectic reaction between γ` and γ, but some recent studies agree with an older diagram due to Schramm, which has a eutectic reaction between the β and γ` phases. This study uses diffusion couple experiments to evaluate the equilibria at temperatures just below the liquidus. The Ni/NiAl diffusion couples were prepared at 1249, 1340, 1355, 1365℃. where the γ` phase formed between β and γ after diffusion heat treatment. The formation of the γ` layer was found to be controlled by volume diffusion. The composition range of the γ` phase with increasing temperatures were increased to the higher Ni composition, which agrees with the Schramm diagram. The interdiffusion coefficient in the γ and β phases has been also determined from the composition profiles of the diffusion couples.

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The physical and mechanical properties of the Cu-6%Ni-3%Mn-6%Sn-0.5%X(Al,Ti,Si)alloys and Cu-6Ni-3Mn-6Sn alloy were strongly dependent on aging condition. The effects of additions of Al, Si and Ti on the mechanical properties and formation of discontinuous precipitate in the alloy have been investigated. In this alloy discontinuous precipitation occurs during aging at 350℃ for 405 min. But addition of Si and Ti in this alloy, discontinuous precipitation occurs much less than the Cu-6Ni-3Mn-6Sn alloy and grain size is decreased. For Cu-6Ni-3Mn-6Sn-X alloy system, spinodal decomposition and transition of metastable phase does not occur but discontinuous precipitation decreased with addition of 0.5% Si, Ti and Al respectively. Also grain size is reduced by addition of 0.5% Si and Ti on Cu-6Ni-3Mn-6Sn alloy because of forming interphase in grain boundary.

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It is known that corrosion resistance of Zr-Nb binary alloy is sensitive to the microstructural changes with heat treatment. Therefore, microstructural observation and corrosion test were performed for the specimens that were heat treated with different cooling rate and annealing temperature. Corrosion resistance was deteriorated with increasing supersaturated Nb concentration in matrix and increasing area fraction of β_(Zr) phase. And it was observed that the amount of supersaturated Nb in matrix is more effective to the deterioration of the corrosion resistance than the amount of the β_(Zr) phase in the same alloy system. During the corrosion test in steam at 400℃ for 180days, the fine β_(Nb) phases were precipitated at α` needle boundary and twin boundary in the case of the specimen having martensitic structure, and the decomposition of β_(Zr) to (α_(Zr)+β_(Nb)) phase occurred in the specimen having Widmansta¨tten structure.

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In this study, the effect of Mn and Zr content on aging behavior and tensile properties of Al 7075 alloy was investigated when the excess Mn and Zr over the equilibrium solubility was added by the rapid solidification method. Flakes of the alloy containing different amounts of Zr were fabricated by atomizing the alloy and subsequently splat quenched on a rotating water-cooled copper drum. The flakes was extruded after the cold compaction and degassing and the followed by T6 heat treatment. Microstructure observation, plane analysis, room and high temperature tensile test and hardness test were pursued. To observe the effect of Zr and Mn on the mechanical behaviour of the alloys, some of the specimens were solutionized and then tensile tests were carried out. As the result of that, the Zr and Mn dispersoid in the alloy is found to increase the strength significantly without losing much elongation.

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This paper describes the tension-tension fatigue properties of high-carbon steel wire containing around 0.6wt.% C, which is used as a stranded wire for ACSR(Aluminum Stranded Conductors Steel Reinforced) in transmission power lines. ACSR which consists of galvanized steel strand and aluminum core always experiences serious vibration by wind. Therefore, it is very important to clarify the fatigue property of core wire for ACSR to determine its lifetime and stability of power delivery. Since steel wires are produced by a wire drawing process, they possess a very long fiber-lamellar microstructure which has a very short inter-layer distance between ferrite and cementite layer. The long fiber-lamellar microstructure is expected to have a different fatigue behavior compared to conventional plate and bulk-type materials. In order to characterize the fatigue property of steel wire having the unique microstructure mentioned above, tension-tension fatigue tests were carried out on specimens drawn to various strains. The fatigue strength was 106.7㎏f/㎟ at ε=1.79, and 92.0㎏f/㎟ at ε=1.19, which showed an inverse relationship with drawing strains. The fatigue strength of a hard-drawn wire was as high as 66∼70% level of its tensile strength. This value was very high compared to that of rolled or full-annealed materials, which exhibited 40∼60% level of their tensile strength. The high fatigue strength is attributed to the very fine elongated pearlitic microstructure formed by the drawing process, which suppresses formation and growth of microcracks. A good correlationship between theoretical fatigue strength and experimental one was found, which meant that yield and tensile strength were the main factors to affect the fatigue property of the steel wire.

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Silicon carbide was synthesized by a combustion synthesis process using exothermic mixture of Mg and (-C₂F₄-) as an activated additive, silicon and carbon. Silicon carbide was synthesized differently with the addition of the activated additive. Especially, with 25wt.% of the additive, better conversion of Si to SiC was obtained. For the types of carbon, it was observed that carbon black and activated carbon showed better reactivity than graphite. In regard of the molar ratio change, when the molar ratio of silicon vs. carbon was 1:2, Si was converted to silicon carbide completely. Among the products, MgF₂ was entirely removed by leaching for 4hrs. at a mixture of 10vol.%(HNO₃+HF)+90% water.

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The oxidation behavior of the iron aluminides and the alloy of the same kind containing zirconium in air at 1200℃ has been examined. The oxide formed on the zirconium free Fe₃Al is highly convoluted and consists of equiaxed grains. On the other hand, with addition of zirconium to the Fe₃A1, distinct changes occur in the oxide morphology. The oxide is less convoluted and consists of columnar grains. The main factor responsible for this change is the facts that addition of zirconium into the external oxide suppresses the diffusion of aluminum within the external oxide. Other secondary advantages resulting from the addition of zirconium in the Fe₃Al is the strengthening of the Fe₃Al. Convolution of oxide can be aided by a weak substrate and weaker alloys would be expected to have more convoluted scales upon exposure to an oxidizing environment at sufficiently high temperature.

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The electrochemical properties of amorphous vanadium pentoxide films fabricated by reactive r.f.-sputtering have been investigated by galvanostatic charge/discharge cycling experiment, AC impedance spectroscopy, and galvanostatic intermittent titration technique (GITT). As x in Li_xV₂O_(5-y) increased (x=0∼2.0), the electromotive force of Li｜1 M LiClO₄-propylene carbonate｜V₂O_(5-y) cells decreased gradually without potential plateau or potential step, demonstrating that an abrupt structural change did not occur in the whole lithium content. Impedance spectra of the cells consisted of a high frequency arc, a low frequency straight line, and a middle frequency Warburg impedance line. Equivalent circuit deduced from Nyquist plot suggests that lithium intercalation reaction consists of three consecutive steps of charge transfer at the electrolyte/cathode interface, diffusion into the film and charge saturation. Chemical diffusivity of Li^+ in Li_xV₂O_(5-y) film, measured using GITT was determined to be 4×10^(-13) to 7×10^(-14)㎠/sec in the lithium content range investigated. The component diffusivity of lithium decreased linearly with lithium content from 9×10^(-14) to 5×10^(-15) ㎠/sec, owing to the decrease in the number of vacant sites available for jumping of lithium atom.

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Near-bamboo interconnects have been reported to have the worst electromigration reliability. Using 1-dimensional computer simulation, the mechanical stress evolution and failure resulting from electromigration in near-bamboo Al interconnects are investigated. We vary the length of (polygranular) cluster and the distance between via and cluster. At initial stage, stress evolves fast in cluster region and forms a nearly straight profile over a whole interconnect at steady state. Cluster positions do not affect stress profiles at steady-state. Interconnects fail at two different positions: via and cluster end. As the distance between via and cluster decreases and the cluster length increases, cluster ends are easier to be failed. Transition of failure sites is considered to be a reason for multi-modal failure distributions reported experimentally for narrow interconnects.

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The crystallographic orientation analysis over the bonded region in transient liquid phase (TLP) bonded joints of Ni-base single crystal superalloy, CMSX-2 was investigated using MBF-80 insert metal. TLP bonding of CMSX-2 was carried out at 1173∼1573K for 0∼19.6ks in vacuum. The (001) orientation of each test specimen was always aligned perpendicular to the joint interface. The (200)-pole figure and the stereographic triangles for three directions using the electron back scattering pattern (EBSP) method indicated that each analyzed point was projected at the almost same location for any directions. For as-bonded and post-bond heat treated specimens, all analyzed points possessed the almost same orientation across the joint interface and misorientation was negligibly small. HRTEM observation revealed that the atoms were arranged continuously across the bonded interface and quite coherent at the bonded interface. It was confirmed that epitaxial growth of the solid phase occurred from the base metal substrates during isothermal solidification and single crystallization could be achieved.

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