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Amorphous Ni_xZr_(100-x)(35≤×≤75) powders were produced by mechanical alloying of elemental powders and the short range order of the amorphous Ni_(35)Zr_(65), Ni_(45)Zr_(55), Ni_(55)Zr_(45) and Ni_(65)Zr_(35) alloys was characterized using X-ray diffraction. The partial interference functions, I_(NiNi)(K), I_(NiZr)(K) and I_(ZrZr)(K), were calculated from the total interference functions of the latter three alloys. The nearest neighbor distances for Ni-Ni, Ni-Zr and Zr-Zr atomic pairs in the amorphous Ni-Zr mechanical alloys turned out to be 2.400 2.654 and 3.282Å, respectively. The coordination number was 12.4∼12.9 depending on the composition. It was concluded that the atoms in the amorphous Ni-Zr alloys didn`t behave like hard spheres and arrange themselves almost randomly even though there seemed to be a little tendency of preference for like neighbors. The total reduced atomic distribution functions of the amorphous Ni_(35)Zr_(65) alloys produced by mechanical alloying and liquid quenching looked alike but some differences were found in their partial functions.

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The pitting behavior of ion-nitrided austenitic stainless steels was investigated by electrochemical methods. Ion-nitriding was carried out at 380 and 550℃ for 10hrs. Passive film breakdown potential(E_b), corrosion potential(E_(corr)) and repassivation potential(E_r) of ion-nitrided AISI 316L stainless steel(SS) were higher than those of ion-nitrided AISI 304LSS, whereas critical anodic current density (I_c) and current density at passive region(I_p) were lower. The pitting resistance of ion-nitrided AISI 316LSS appeared to be better than that of AISI 304LSS and the corrosion morphology showed severe pitting in the case of ion-nitrided AISI 304LSS at 550℃ for 10hrs.

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The stress-rupture properties and fatigue behavior of Al-10wt.%Ti alloy, which has been produced by mechanical alloying, followed by hot extrusion, were investigated. Creep strength of MA Al10wt.%Ti and MA Al-0wt.Ti alloys at 300℃ were two and three times as much as that of conventional precipitation-hardened Al alloys, because dislocation mobility was reduced effectively by the presence of thermally stable dispersoids. The creep mechanism of MA Al-10wt.%Ti is considered to be primarily controlled by deformation between dispersoids and grain boundary dislocations in the grain boundary. Room temperature fatigue strength of MA Al-10wt.%Ti alloy was similar to that of Al 7075 but superior to Al 2024. As the temperature increased from room temp. to 300℃, 400℃, the fatigue ratio decreased from 0.36 to 0.3 and 0.27, respectively, and the number of crack initiation at the surface and secondary crack were increased.

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TiAl intermetallic compounds based on γ-phase were consolidated by hot extruding the mixture of elemental powders of Ti, Al and other additives. The effects of alloying elements and heat treatment on tensile ductility were studied. During hot extrusion, the powder mixture was fully densified and the added B, Cr, Mn, Mo or Nb was completely dissolved into γ phase. The alloys heat-treated at 1250℃ followed by 950℃ after hot extrusion consisted of equiaxed γ and lamellar γ+α₂ phases. Addition of Mn or Mo refined the grain size and improved the room temperature tensile elongation up to about 4%. The improvement in tensile ductility of the tested alloys was attributed to fine grain size by added elements and proper control of the amount of α₂(about 20vol.%).

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The segregation established at the interfaces of gray and ductile iron has been examined by using Auger electron spectroscopy. This work pursued the effect of Mg on the interface chemistry as a first step to understand the microstructural modification caused by the doping addition of Mg into cast iron melts. In gray iron, S was the major segregant to both the iron/graphite and iron/iron interfaces. The effect of Mg in ductile iron was demonstrated by the clean interfaces with no such impurity segregation as observed in gray iron. Oxygen segregation was not significant at both the gray and ductile iron interfaces contrary to the results of ocher works. The segregation at, the iron/iron interface greatly supported the results obtained from the iron/graphite interface, especially with regrad to the controversial O segregation and also the segregation behavior of S as affected by Mg.

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The coarsening behavior of δ′(AI₃Li) phase has been studied in various alloys of Al-Li, Al-Li-Cu and Al-Li-Cu-Mg systems using transmission electron microscopy. The coarsening kinetics are well governed by Ostwald ripening theory in all cases. The ccarsening rate depends sensitively on the volume fraction of δ′ phase particulary in binary system, which conforms relatively well to the MLSW theory. The addition of Cu in Al-Li binary alloy ○ds to accelerate the coarsening rate of δ′ phase. This is believed to be due to the variation of δ′ interfacial energy. The addition of Mg in Al-Li-Cu ternary alloy tends to reduce the δ′ coarsening rate. This is because the precipitation of S′ phase has an effect to reduce the diffusivity of Li atom by depleting the concentration of vacancy.

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