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Precipitation and dissolution reactions in Al-2.33wt%Li-0.32wtZr alloy were examines by employing adiabatic scanning calorimeter. The results obtained were as follows. The δprecursor phase was appeared immediately during quenching and was precipitated at the higher temperature(433k) than the miscibilty gap of Al-2.33wt%Li binary a1loy. It dissolved in the 360-463K temperature range with an enthalpy typical of GP zones as like other Al base alloys, and the kinetics of its dissolution were also similar to those of other GP zones. Two endothermic reactions appeared in the lower temperature than the reversion temperature of δphase were corresponding with those of dissolution of GP zones in Al-Li binary alloys.

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The shape memory ability, microstructure and crystal structure in Cu-21.30Zn-5. 36Al(wt.%) shape memory alloy have been extensively studied as a function of thermal cycling. Crystal structure of quenched alloy is M18R(β₁`) martensite, and it become fragmentary with increasing thermal cycles. Shape memory ability is decreased and stress-induced 2H(γ₁`) martensite and residual parent (DO₃) phase are founded during thermal cycling. Reversible shape memory effect is occurred according to thermal cycling at 473K, in which martensite plate, only 18R structure, is occurred incorporation and intersection.

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A computer model has been developed to simulate the behavior of lead and arsenic in the copper matte converting at the TSUMEB smelter. The analysis of the behavior of lead and arsenic was performed based on the previous modeling work and some thermodynamic data were updated and modifications made to meet the TSUMEB`s high lead and arsenic content in matte. Results of the simulation showed that the most of the lead and arsenic was removed in the slag blowing stage, and therefore the emphasis of this work is on the slow blowing. The predictions showed good agreement with operating data. Some discrepancies during early part of the slag blow were attributed to the reaction between the oxide slag (remained from previous batch) and matte before the slag blow.

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Recently, new and improved brazing filler metals with selffluxing has been produced by rapid solidification in Cu-P based alloys. As the industrization goes on, it is required to decrease properly the brazing temperature of filler metals with good brazed joint characteristics such as mechanical strength, electrical properties etc. The brazed joint characteristics and the formation of amorphous were compared Zr-containing Cu-P based filler metal with Zr-free Cu-P based filler metal. As a result, it has been concluded that the brazed joint characteristics were simillar each other between the above two filler metals, and grass forming ability was accelerated by Zr addition.

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The effect of resolution treatment on the impact toughness of martensite in Fe-18%Ni alloy have been studied. The solution-treated specimen showed brittle-fracture at 196℃, but the low-temperature toughness was improved greatly by resolution treatment at temperature range of 650℃ to 750℃ above A point for short time. The grain size of austenite was refined with resolution treatment time due to recrystallization of austenite, but the toughness was decreased by occurring intergranular-fracture. The martensite formed from the unrecrystallized reversed austenite showed fine block structure within a grain and zig-zagged prior austenite grain boundary. Grain boundary strengthening by the latter seems to be more effective to considerable improvement in low-temperature toughness.

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In order to compare the slip deformation modes of Fe-3%Si singe crystals created by mechanical indentation and Nd : YAG laser pulse, they were indented with the Rockwell diamond brale and irradiated with the Nd : YAG laser pulse. The slip traces generated on (111) and (001) surface planes were analysed by trace analysis method. The microstructures in both deformed specimens were observed by Nomarski microscope and TEM. Mechanical indentation on (111) and (001) surface planes resulted that the slips had taken place on {110} and {112} planes along $lt;111$gt; direction. Meanwhile laser irradiation showed that the slips had also taken place on {123} planes in addition to {110} and {112} planes due to thermal effect. It seems that a strain rate had larger effect on the spacing of slip bands in Fe-3% Si single crystal compared with temperature increase. Dislocation density was higher in mechanically indented specimen and they were tangled each other. Mean while dislocation density was lower in laser irradiated specimen and the were aligned along the characteristic orientation.

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From data analysis of previous1y reported researches in liquid quenching alloys. the logarism of cooling rate shows the linear relation to the atomic size effect value within the eutectic composition and this relation is applied to ternary alloys having similar chemical affinity. The value of atomic size effect decreases in alloys having a large chemical affinity. The atomic size effect as a parameter for the glass forming ability has to be treated as a variable dependent upon the cooling rate and the chemical affinity between the constituent elements.

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Spherodization and cold forgeability of 4140 steel have been studied by two stage heat-treatments. The temperatures of the first stage heat-treatment (T-1) were 740℃ and 760℃, which are a little above A_I point and A_(CI) point, respectively. The second stage (T-2) heating temperature was 700 ℃. Heating times were varied at these temperatures. The cooling rate from T-1 to T-2 temperature was 300 ℃/h, which is relatively high speed. Lamellar carbides were not formed during the fooling stage from T-1 to T-2 temperature, when the T-1 temperature was 740℃. This result is contrary to other authors` results. They found the lamellar carbides when the cooling rate from T-1 to T-2 is not low. However, the lamellar carbides were produced at this stage when T-1 temperature was 760℃. Among the two stage heat-treatments studied, the T-1 treatment at 740℃ for 3 hours was the most effective process for the spherodization and cold forgeability, not much depending on the T-2 treating times.

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To study the weldability of the newly developed AA7019 aluminum alloy, both mechanical and corrosion resistant properties of its Gas Metal Arc (GMA) weldment were evaluated. GMA butt welds with A5356 filler metal were made in the flat and vertical positions of 30㎜ thick plates. The results of mechanical tests performed on test coupons, which were removed from the welded plates (natural1y aged at least 30 days), were correlated directly with softening and subsequent recovery of the strength in the HAZ(Heat Affected Zone) whereas the strength of the weld metal was not significantly affected The susceptibility to the corrosion and stress-corrosion cracking in an aqueous salt solution (3.5wt.% NaCl) was also evaluated in each weldment. A combination of susceptible microstructure and galvanic coupling was determined as the cause of SCC(Stress-Corrosion Cracking) failure, which occurs preferentially in the HAZ adjacent to the weld bead. Results of this study suggest that development of new filler metals higher in s rength and avoiding severe corrosion environment be considered for the optimum application of GMAW of AA7019 alloy.

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The behaviour of stress corrosion(SC) crack initiation and propagation of Type 304 stainless steel in 35 wt% MgCl₂ has been studied as a function of temperature and applied stress at the applied electrochemical potential of-106mV_(SHE) by using electrical potential method. In the present study. the electrical potential method allows to differentiate the incubation period from the propagation period for SC crack. The optical microscopy revealed that the pit is a primary source of SC crack initiation under the applied stress lower than yield strength. SC crack initiation stage is composed of three steps, 1) pit initiation, 2) pit growth to critical size, and 3) crack propagation in the lateral and the through-thickness directions. The portion if anodic dissolution trenches to pits as sites of SC crack initiation increased with applied stress higher than yield strength. The activation energy of the electrochemical reaction contribution to the SC crack initiation and the energy of the stress contribution to the SC crack initiation under 212MPa are evaluated to be 30.5 kJ/㏖ and 14.0 kJ/㏖ respectively. The fractography of SC crack propagation showed the transition of fracture mode from fully transgranular mode to the mixed zone with intergranular mode in the interior of the specimen. The intergranular portion is nearly independent of temperature, however it increases with the applied stress.

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