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In the previous study, the β+γ` alloy containing Ti and C showed a more refined mesh microstructure than the lamellar microstructure. This study revealed that the titanium among alloying elements helped to refine the microstructure. The M_s temperature of NiAl lowered rapidly with an increasing titanium content. This effect therefore contributed to the formation of the fine microsturucture. In the case of a low titanium content(below 2.2at.%), the M_s temperature was above ∼255℃, and when the martensite was heated, the exothermic β`→Ni_5Al₃ transformation appeared first. Because the martensite twins could be inherited during the β`→Ni_5Al₃ transformation, the lamellar β+γ` structure similar to martensite plates was finally formed. However, in the case of a high titanium content, the M_s temperature sufficiently lowered, so the endothermic β`→β transformation could occur before the β`→Ni_5Al₃ transformation. The endothermic transformation extinguished the martensite plates, therefore allowing the mesh microstructure to be independently formed from the martensite plates.

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δ`-PFZ growth behaviors in Al-Li alloys at various aging conditions were investigated mainly by TEM observations. The widths of PFZs were increased with aging time and aging temperature and their growth is proportional to the square root of aging time. The alloy containing Sc showed a smaller value of growth rate constant and larger activation energy for the PFZ growth than those of other Sc-free alloys. These facts indicate that diffusion process of Li solutes via vacancies could be precluded or limited by Sc in solution. In the Sc containing alloy, high density of dislocations surrounded by coarsened Al₃Sc particles were observed in the overaged condition. These dislocations can be closely linked to the reduction of growth rate of the PFZ, considering that they provide sink sites for lattice vacancies, finally leading to suppress the diffusion of Li solutes toward grain boundaries.

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Ti-Al intermetallic compound thin films were deposited both at room temperature and at elevated substrate temperatures of 573 to 773K by using a two-facing-targets-type DC sputtering system. Atomic compositions of the binary Ti-Al alloy targets are Ti-rich(75Ti-25Al(atm%)), stoichiometry(50Ti-50Al(atm%)) and Al-rich(25Ti-75Al(atm%)). The crystallization processes and phase transformations of Ti-Al thin films were investigated by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The as-deposited films were also annealed successively and isothermally at different annealing temperatures of 773, 873 and 973K. The microhardness of Ti-Al thin films was measured by a dynamic hardness tester. The crystallized phases of as-deposited films, deposited at room temperature and elevated substrate temperatures, were different. Phase transformations during annealing treatment are α-Ti+Ti₃Al→α-Ti+Ti₃Al for Ti-rich films, amorphous/Ti+(Al)→TiAl+Ti₂Al_5+Ti₃Al for stoichiometry and Al+(Ti)/TiAl₂/Ti₂Al_5→α-TiAl₃/Ti₂Al/TiAl₃ for Al-rich films. The analyses of the selected area electron diffraction patterns were in accord with X-ray diffraction results. The above results are discussed in terms of crystallized phases and microhardness.

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Indentation cracking test has been used to evaluate the adhesion of wear-protective coatings such as diamond film. This test can induce interface crack by applying indentation load to the film. A reciprocal of the rate of change of interface crack radius with indentation loads(dP/dc) has been generally used as the qualitative criterion of the adhesion. This concept is, however, valid only when comparing the adhesion in the same materials because the material properties are not considered in dP/dc. In this study, therefore, for the more reliable evaluation of adhesion, the critical energy release rate was obtained by analyzing the dependency of interface crack on indentation load. Stress fields in film were from the indentation stress field in substrate using the condition of strain continuity at the interface. From the analytical model, the strain energy released by film delamination was formulated. Finally, the critical energy release rate was obtained as the quantitative function of dP/dc and was compared with the results from scratch test. Using the proposed analysis, the adhesion of diamond-like carbon(DLC) film deposited on AISI D2 steel was evaluated.

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A correlation was made of microstructure, high-temperature wear resistance, and surface roughness in hardfacing alloys reinforced with complex carbides. The hardfacing alloys were deposited twice on a low-carbon steel substrate by a submerged arc welding method. In order to investigate the effect of complex carbides, different fractions of FeWTiC and WTiC carbide powders included inside hardfacing electrodes were employed. Hot rolling simulation test was carried out using a high-temperature wear tester capable of controlling speed, load, and temperature. Microstructural analysis indicated that cuboidal and rod-type complex carbides were homogeneously distributed in the bainitic matrix. As volume fraction of these complex carbides increased, hardness and wear resistance increased. The alloy hardfaced with FeWTiC powders contained more complex carbides in the harder matrix than those hardfaced with WTiC powders because of efficient melting and solidification during hardfacing, and thus showed the best wear resistance and excellent surface roughness. Hardness, wear resistance, and surface roughness of the hardfacing alloys reinforced with complex carbides were improved in comparison with high speed steel rolls because of the homogeneous distribution of hard and fine complex carbides in the bainitic matrix.

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Hot cracking formation and its mechanism in invar alloys during continuous casting were investigated. It was found that the solidification range was not related to the hot cracking susceptibility in invar alloys. The hot cracking range (= liquidus temperature - ductile to brittle transition temperature), was found a reliable index for the prediction of hot cracks. Hot cracking susceptibility in invar alloys is greatly affected by cooling rates. With increase in cooling rates from 10 to 100 ℃/min, the ductile to brittle transition temperature shifted significantly to the higher temperature from 1320 to 1390℃ (ΔT=70℃). A hot cracking mechanism for invar alloys has been proposed. Hot cracks formed in fast-cooled alloys occurred between the primary dendrites due to the equiaxed structure. However, hot cracks formed in slow-cooled alloys occurred between the grain boundaries due to the columnar structure.

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The strength and electrical conductivity of Cu-7Cr-0.9Ag-0.3Fe and Cu-7Cr-0.9Co-0.4Fe microcomposite plates obtained by cold rolling combined with intermediate heat treatments have been investigated. During cold working the primary and secondary dendrite arms were aligned along the rolling direction and elongated into filaments and also coarse Cr particles were found to be distributed uniformly in the matrix after thermo-mechanical deformation processing. The ultimate tensile strength and the conductivity of the Cu-Cr based microcomposites containing Ag were higher than those of Cu-Cr microcomposites containing Co. The strength of Cu-Cr composites was dependent on the spacing of the fine Cr filaments and volume fraction of the coarse Cr particles in accordance with a rule of mixture. The fracture surfaces of all the specimens showed ductile-type fracture.

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This paper presents the results of a study that was undertaken to optimize the ratio of the components of a new multicomponent inhibitor blend composed of orthophosphate/ phosphonates/ acrylate copolymer/ isothiazolone. Here, Orthophosphate functions as a corrosion inhibitor. Phosphonates function as a corrosion and scale inhibitor. An additional role of the polymer in this blend is the control of scale. On the one hand, isothiazolone is used as a biocide. The effect of newly developed inhibitor was studied through weight-loss tests, electrochemical tests, scale tests, microorganism tests and surface analyses. The obtained results showed that developed inhibitor revealed a very good corrosion, scale and microorganism inhibition simultaneously. Weight-loss tests, electrochemical tests and surface analyses indicated that blended inhibitor acted as anodic and cathodic inhibition forming bi-polar layer contained calcium phosphate, calcium phosphonates, and iron oxide complex. Inhibitor used in this study exhibited crystal modification effect for calcium carbonate scale. In addition, all kinds of microorganisms used in this study were inhibited effectively.

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The effects of Sn on the corrosion behavior of the Zr0.8NbxSn (x = 0.2, 0.4, 0.6, 0.8 and 1.0) alloys in 360℃ water, 400℃ steam and 360℃ LiOH solution were investigated. The specimen was annealed at three different conditions of 470℃, 490℃ and 510℃. The microstructures and the oxide characteristics were analysed by using TEM and XRD, respectively. Hydrogen absorption test was performed to find the correlation between corrosion and hydrogen pick-up fraction. Tensile tests were additionally performed. The corrosion rate in 360℃ water test was increased with addition of Sn, while in LiOH solution the corrosion rate was decreased. As the corrosion rate was increased, the fraction of tetragonal-ZrO₂ in oxide was decreased. The opposite result of corrosion behavior would be results from the different role of Sn on the corrosion mechanism in water and LiOH solution. The tensile strength was increased with the addition of Sn due to the solid solution hardening and precipitate hardening.

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Two kinds of the specimens made of Zr-Sn-Nb experimental alloys were investigated for their corrosion behaviors and mechanical properties after some different thermo-mechanical treatments including the final heat treatments as stress-relived (SR) at 470℃ and recrystallized (RX) at 520℃ for 2.5 hours, respectively. The corrosion tests were carried out in the autoclaves containing 360℃ water, 400℃ steam and 360℃ aqueous LiOH(70 ppm) solution. Microstructures of the tested specimens were analyzed using an optical microscopy and TEM, and those of their oxides using small angle XRD method. All of the tested specimens showed higher corrosion rates in the steam than in the water or the aqueous LiOH solution. The specimens having lower Nb and Sn content showed a little better corrosion resistance in all the environments than those having higher Nb and Sn content. It was found out that SR specimens had higher t-ZrO₂ fraction to m-ZrO₂ showing better corrosion resistance than that of RX ones as well as the SR ones had more hardness, tensile strength, and creep resistance than the RX ones.

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