http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
이후철,이주완 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.4
The effects of Sn addition on the internal oxidation of Ag-Cd alloys were studied. Four types of Ag-15Cd alloys with p.3, 0.5, 0.8, snd 1.5 wt% Sn were prepared by induction melting in Ar atmosphere. Alloys were internally oxidized at 677, 735 and 782 C with 1.0-3.0×10^5 Pa oxygen partial pressure. Internal oxidation increased the hardness of all alloys by 65-100%. Alloys with higher Sn content showed higher hardness. Oxidation condition proved to have significant influence on the oxidation microstructure and wear resistance. The oxides observed after internal oxidation were identified as SnO₂, Cd₂SnO₄ and CdO. Cd₂SnO₄ particles were embedded within CdO particles. The mechanism of oxidation is considered as follows. First. Sn is oxidized to form SnO₂, then it transforms to Cd₂SnO₄ by furthier reaction with Cd and O. Finally CdO grows around the Cd₂SnO₄ particles. Because Cd₂SnO₄ particles act as nuclei far CdO precipitation, finer dispersion of oxides occurs in higher Sn content alloys resulting in higher hardness and improved wear resistance of the alloy.
Fe-Ni-Mn-Mo-Ti 강의 석출반응과 기계적성질에 미치는 Cr 의 영향
이후철,문승호 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.8
The precipitation reaction and mechnical properties of Fe-8Ni-3.5Mn-5Mo-1Ti alloys without and with 5% Cr addition were investigated. Two stages of age-hardening due to the precipitation of rod-type η-Ni₃Ti and spherical-type Fe₂Mo intermetallics were observed. The addition of chromium increased the age hardening rate and peak hardness of the base alloy. especially at the second hardening stage. From TEM analyses, it is concluded that chromium addition refines the precipitation, suppresses the coarsening of rod type precipitates and considerably promotes the formation of spherical type precipitates during the second stage of aging. The Fe-8Ni-3.5Mn-5Mo-1Ti alloy showed intergranular and cleavage fracture during first stage of aging at 520℃, but higher ductility with higher strength was achieved in the 5% Cr-bearing alloy. Lower grain boundary segregation of the embrittling alloying elements Mn and Ti, etc. in the Cr-bearing alloy was suggested. The optimun combination of strength and ductility was obtained in the Fe-8Ni-3.5Mn-5Mo-1Ti-5Cr alloy aged at 520℃ for 8 hours and obtained values were σ_(0.2) = 1611 MPa. σ_t = 1739 MPa and ε_f = 9.8%.
이후철 대한금속재료학회 ( 구 대한금속학회 ) 2003 재료마당 Vol.16 No.1
Ti첨가 IF 강에서 미세한 TiC의 석출은 재결정 거동과 재결정 집합조직 또는 기계적 특성에 상당한 영향을 미치게 된다. 이러한 미세한 TiC의 석출은 합금의 조성이나 열연 공정에 따라 달라지게 되며 일반적으로 열연 공정시 평형 석출이 일어나지 않는 것으로 알려지고 있다. 열연 공정에서 TiC의 석출이 충분하지 못한 경우 열연 핫코일 중에는 상당량의 Ti 및 탄소가 기지에 고용되게 되며 이들 과고용된 Ti 및 탄소는 냉 연 후 재결정 아닐링 과정에서 전위나 아결정립계에 석출하게 된다. 이러한 석출은 IF 강의 회복을 지연시키게 되고 따라서 재결정을 지연시켜 재결정 온도의 상승을 가져오게 된다. 따라서 재결정 온도 및 집합조직을 유리하게 관리하기 위하여서는 가급적 열연 공정에서 Ti와 탄소를 조대한 Ti4C2S2 또는 Ti4C2S2+TiC 복합석출물 형태로 석출 완료시키는 것이 바람직하다고 하겠다.
구리 함유 극저탄소강의 집합조직발달에 미치는 코일링 온도의 영향
이후철,서동우,양영철 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.11
The effects of coiling temperature on the texture development and mechanical properties of a 1wt% copper containing extra low carbon steel were investigated. An experimental alloy was vacuum induction melted, forged and then hot rolled. Coiling process was simulated by annealing at 500℃ or 700℃ for 1 hour and was followed by furnace cooling. After the coiling simulation, specimens were cold rolled with reduction ratio of 80% or 90%. ε-Cu precipitates in ferrite matrix are rarely observed in specimens coiled at 500℃ and coiling does not affect the development of {111} recrystallization texture. However fine ε-Cu particles are precipitated in α-Fe matrix when coiled at 700℃ and the precipitates remarkably increase the intensities of α-fiber texture components during cold rolling, retard the recrystallization during annealing and suppress the development of {111} recrystallization texture. Coiling temperature does not affect the tensile properties of 1wt% copper containing steel but, in specimens coiled at 700℃, suppression of {111} recrystallization texture results in lower mean plastic strain ratio.
초내열합금 Mar-M247LC 의 저주기 피로수명 평가
이후철,최병학 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.9
The low cycle fatigue (LCF) life prediction model for directionally solidified(DS) Mar-M247LC superalloy has been stuided as the variables of plastic strain and stress range. The plastic strain range is the general criterion for LCF life prediction model like Coffin-Manson equation. On the other hand the stress range is also important to the criterion for LCF life evaluation. The complex effect of plastic strain and stress range on LCF life could be considered as the calculation of hysteresis loop area in fatigue testing. The LCF life as a function of plastic strain and stress range has been measured at the variables of strain rate and DS direction.
이후철,노재상 대한금속재료학회(대한금속학회) 1982 대한금속·재료학회지 Vol.20 No.7
Autovacuum cleaning and hot rolling processes were applied to produce stainless clad steel. The effects of manufacturing variables on the bonding shear strength were investigated. The principal factor that controls the bonding shear strength was known to be the rolling reduction ratio and good bonding strength over 30㎏f/㎟ was obtained at over 40% rolling reductions. Thickness of the nickel layer or annealing time showed little effects on the bonding strength. The effect of surface roughness was greatly reduced at over 50% rolling reductions. Rearrangement of mild steel-nickel interface was observed after annealing process but the rearrangement did not affect the bonding strength when the rolling reduction is over 50%. Porosities were observed after up to 40% rolling reductions but were barely noticed after 60% rolling reduction. Carbon diffusion was not significant right after hot rolling but occurred very rapidly during annealing process.