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기계적합금화로 제조된 Ni-Cr-W 합금에서 γ'- 석출물 및 Y2O3 분산물이 고온크리프성질에 미치는 영향
권숙인,조준식 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.6
The effects of γ' precipitates and Y₂O₃, dispersoids on high temperature tensile and creep properties of mechanically alloyed Ni-20Cr-4W alloy were studied. The zone annealing was performed to increase grain size and grain aspect ratio. The zone annealing method was found very useful to increase high temperature strength and creep resistance. The addition of Y₂O₃into Ni-20Cr-4W alloy not only gave this alloy dispersion hardening, but also improved thermal stability of γ' precipitates at high temperature. Up to 950℃, γ' precipitates contributed to high temperature properties more efficiently than Y₂O₃dispersoids. However, the contribution of Y₂O₃to high temperature strength was greater in creep than in high temperature tension. The mechanically alloyed Ni-20Cr-4W alloy showed the creep threshold stress.
Mo 첨가에 의한 Zr 계 합금의 원자로심 재료 특성 향상
권숙인,김명호,이정횡,황선근 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.6
The role of Mo in Zr-based alloys was studied in terms of the microstructure, texture and corrosion resistance. The base compositions of the experimental alloys were Zr-1Nb and Zr-1Nb-1Sn-0.1Fe to which Mo was added in varying amount up to 0.5%. Buttons of 300 g in weight have been produced by plasma arc remelting (PAR) and processed in sequence by hot forging, hot rolling, beta annealing, cold rolling and recrystallization annealing. It was confirmed that Mo addition resulted in grain refinement: beta grains as well as recrystallized alpha grains. This, in turn reduced the formation frequency and the size of twins and relaxed of the surface normal preferred orientation, f_n. In the corrosion test in water containing 220 ppm LiOH (360℃, 17.9 ㎫), the alloys with up to 0.2% Mo showed a good corrosion resistance whereas that with 0.5% Mo showed a degraded resistance. Apparently, the corrosion resistance was related to the density and morphology of the second phase particles. Alloys containing fine and uniformly distributed β-Nb particles showed good corrosion resistance whereas those containing excessive number or undesirable distribution of particles particularly in uncrystallized region showed degraded corrosion resistance. Overall, the present study suggests that alloying of up to 0.2% Mo should be favorably considered for improving the mechanical properties without impairing the corrosion resistance of Zr-based alloys for nuclear core applications.
권숙인,조윤성 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.1
The effect of strain induced martensite on the fatigue behavior of AISI 304 austenitic stainless steel was investigated. During low cycle fatigue, the austenitic stainless steel showed a continuous cyclic hardening until fracture. The extent of cyclic hardening increased with decreasing austenite stability. The austenite stability was controlled by different aging time and temperature, which resulted in different carbide morphologies. The fatigue crack propagation rate near △K_(th) varied also with the austenite stability inside the plastic zone at the crack tip. Especially, the near-threshold fatigue crack propagation rate of the grain boundary carbide precipitated condition was the lowest. This was considered to be due to the roughnessinduced closure caused by intergranular facet. A new model for the intergranular facet formation and the fatigue crack propagation of grain boundary carbide precipitated condition was proposed.