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The characteristics of mart ensitic transformation and martensite substructures in Ni(Cu)Al alloys containing up to 10 atomic percent Cu were studied. The crystallographic structure of a1l the Ni(Cu)Al martensites was identified to AuCu(I) type and their c/a ratios were decreased with increasing Cu content. Other effects of Cu substitution were as follows : The invariant shear strain was increased up to 0.163 from the near ideal value of 0.129 in NiAl alloy. Hardness of Ni(Cu)Al martensite decreased to 300㎏/㎟from 720㎏/㎟, the hardness of NiAl martensite. Martensite morphologies of Ni(Cu) Al alloys are quite similar to that of NiAl alloys but crossed morphologies are quite often observed in Ni(Cu)Al martensites. Tweed structure was also observed in Ni(Cu)Al alloys.

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Phase relations in the quaternary system of Fe₂O-CaO-SiO₂-A1₂0₃in the temperature range between 1450℃ and 1200℃ were studied. So-called calcium-ferrite was crystallized and its composition and amount were studied. 1) Calcium-ferrite was identified as a solid solution of CaO·2Fe₂03 and CaO·6A1₂O₃ with 3.5 to 6.7 wt% solubility of SiO₂ 2) With increasing the portion of A1₂0₃in the system, the amount of the crystallized calcium-ferrite was increased and the crystallization temperature was enhanced. 3) The solubility of Al₂O₃in the calcium ferrite was increased and the solubility of Fe₂O₃ was decreased with increasing the portion of Al₂O₃in the system. 4) Increasing the portion of CaO in the system landed to increase the amount of calcium-ferrite and enhance the crystallization temperature.

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The magnetic hardening process according to the heat treatment of a Fe-Cr-Co hard magnetic alloy was investigated. It could be described that the magnetic hardening process of this alloy was divided into three parts. In the heat treatment of the first stage, the thermomagnetic treatment, FeCo-rich (α₁) phases were precipitated. The aspect ratio of precipitates was determined in this stage. The heat treatment of the second stage caused precipitates to grow, improving the magnetic properties of the alloy. The alloy became brittle due to the rapid increase of the hardness by the second stage. In the heat treatment of the third stage, the concentration of the matrix (α₂) and the precipitates (α₁) changed gradually with little change in the shape and volume fraction of the precipitates. The coercive fores of the alloy increased largely in this last stage.

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The effects of vacancies and dislocations on the hydrogen diffusion in Cu have been studied at 22℃ by using electrochemical permeation technique. Two kinds of specimens were prepared from cold-rolled Cu specimens. One batch (A) of this material was annealed for 5 min at 950℃ and then quenched in cold water prior to reannealing for various times at 80 and/or 150℃. The other (B) was annealed either for 24 h at 150℃ or for 24 h at 750℃. Hydrogen diffusivity has been measured in the quenched specimen as a function of annealing for various times at 80 and/or 150 ℃. Electrical resistivity measurements of the quenched specimen A indicate that lattice vacancies are annihilated with reannealing at 80 ℃. As reannealing Time increases, the diffusivity increases, suggesting that the vacancies act as trap sites of hydrogen. The apparent diffusivity of hydrogen in the cold -rolled specimen annealed at 750 ℃ is slightly higher than that in the cold-rolled specimen annealed at 150 ℃, suggesting that the dislocations hardly act as trap sites of hydrogen in Cu contrary to BCC metals.

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The floating behavior of non-metallic inclusion and flew pattern of molten steel in continuous casting tundish was studied in respect of chemical reaction engineering. Water model experiment was done in the range of flow rate without surface turbulence (high flow rate) and stagnant zone (low flow rate) in model tundish. In case of no dam, the flow pattern of tundish which was analysed by R. T. D-curve was nearly perfect mixed flow and removal efficiency of inclusion was expressed well as first-order reaction equation of mixed flow reactor: (수식) In case of dam owing to the increased dispersed plug flow volume of tundish, removal efficiency of inclusion was more excellent than that of no dam, and expressed well as first-order reaction equation of mixed model : (수식) It is evident that the use of dam was more effective for promoting the floating removal of inclusion than that of no dam, because dam increased the dispersed plug flow in tundish. It is well agreed to the fact of chemical reaction engineering that the more plug flow volume system (tundish) has, the more conversion (floating removal of inclusion) occurs in system (tundish).

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The effect of microstructure on the fracture toughness of ferrite-martensite bainite steels was investigated with Fe-0.11C 1.64Mn-0.78Si composition. One inch compact tension specimens (1T-CTSs) were machined from hot rolled plates. The microstructure of ferrite-martensite-bainite was introduced to the specimens by the heat treatment of inter critical annealing at 800˚C and isothermal holding at 350C Holding at 350 C increased volume fraction of bainite. while decreased that of martensite, and refined martensite particles. Single specimen unloading compliance method was used in fracture test to obtain J-resistance (J-R) curve and to determine the fracture toughness(J_(IC)). Introduction of bainite to the ferrite-martensite steel1 improved the fracture toughness due to the deformation of bainite which relaxed the stress concentration on the interface of ferrite and martensite. Observation of fractgraphs through the scanning electron microscope (SEM) identified the fracture mechanism of ferrite- martensite-bainite steels as dimple nucleation and crack growth by decohesion of ferrite matrix and second phase particles and by mi crovoid coalescence.

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In manufacturing pressurized heavy water reactor fuel bundles, bearing pads and inter-element spacers are brazed onto Zircalloy-4 cladding tube. To investigate the changes of mechanical properties of the cladding tube caused by the brazing, the phase transformation characteristics were studied under the various heat treatment conditions. The rupture characteristics of the brazed cladding tube were studied by the out-of-pile biaxial burst test and biaxial creep rupture test. The effect of brazing on the mechanical anisotropy was studied by the flow surface technique. The critical cooling rates for different structures could be determined by examining the microstructure : 0.2 ℃/s for the lenticular structure, 2 ℃/s for the parallel plate structure, and 11℃/s for the basketweave structure. The failure occurred in the brazed area under the burst deformation teat at 400℃. However, under the creep test at 400 ℃, the virgin area, i.e., cold worked and stress relieved structure, showed failure. This seems to result from activating of the different slip systems, i.e., {101￣0}$lt;12￣10$gt; in the brazed area and {l1￣01}$lt;112￣3$gt; and {112￣1}$lt;112￣3$gt; in the virgin area, as well as from the different degree of anisotropy. The tensile strength at 400℃ of the brazed area was higher than the one of the virgin area.

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Magnetic measurements on the rapidly solidified(RS) FeAl_(1-x) Ni_x series (X= 0.05-0,35) have been made at temperatures from 77 K up to 750 K, and compared with those of the annealed specimens. It was found that ferromagnetism appeared at the RS alloy with X≥0.25 and alloys with X$lt;0.25 remained superparamagnetic down to 77 K. Annealed alloys showed paramagnetism at X＜0.20, superparamagnetism at X=0.20, and ferromagnetism at X≥0.25. Magnetization increased as X increased. The rapid solidified specimens, in general, showed stronger magnetic behaviors than the annealed ones. X-ray diffraction data revealed that specimens, both the rapid solidified and annealed, were single-phased in B2(CsCl) structure with virtually constant lattice parameter, 2.91 A. The rapidly solidified alloys, however, exhibited some extent of disorder in the site occupancies of Al atoms and Fe atoms. The experimental results were analyzed on the paint of view of the local environmental effect of magnetic atoms.

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Structures and corrosion properties of the low antimony-lead alloys for the lead acid battery electrode were studied by means of metallographic and electrochemical methods. Comparisons were made with pure lead, lead-antimony alloys, and lead-antimonyselenium alloys. The grain size of the alloys was dependent on the antimony content and could be reduced by the addition of selenium. The effect of the grain refining on the corrosion attack in the positive electrode was interpreted in terms of the anodic dissolution of antimony.

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Hypoeutectic Al-9%Si and Al-4.5%Cu alloys were casted in four kinds of ingot case materials with different thermal conductivity, and the solidification phenomenon was investigated by measuring shrinkage cavity, centerline feeding resistance, cooling rate of melt, temperature gradient of ingot cases and interdendritic arm spacings. The ingot case materials studied were flake graphite cast iron(FGCI), CV graphite cast iron(CVGCI), spheroidal graphite cast iron(SGCI) and FGCI/CVGCI/SGCI from the bottom side of an in got case. An ingot case composed of FGC/CVGCI/SGCI showed less shrinkage cavity and centerline feeding resistance than those of either FGCI, or CVGCI or SGCI. The cooling rate of melt was a bout 1.5℃/sec faster at the sideline than at the centerline of the melt. The secondary dendritic arm spacing was measured to be inversely proportional to the cooling rate of the melt.

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