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Fe-10Cr-10Ni-2 W 마르에이징강에서 reverted 오스테나이트의 형태와 결정학적 특징
홍순형,남수우,석진이 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.3
The morphology and crystallographic feature of austenite formed from martensite during aging have been investigated in a Fe-10Cr-10Ni-2W maraging steel. The microstructure of solution-treated sample is fully martensite before aging. Four types morphology, such as lath-like, allotriomorph, Widmansta¨tten and wedge-shaped austenite. appeared in this maraging steel during aging. The reverted austenite is formed having both a Kurdjumov-Sachs(K-S) orientation relationship and a Nishiyama(N) orientation relationship with martensitic matrix. Furthermore, a wedge-shaped austenite is found to have a twin relationship between adjacent austenites. The twinned austenite is observed to have a very sharpy twin boundary, and longitudinal direction of the twin boundary is dependent upon both the beam direction and the orientation relationships between austenite and martensite.
Vacuum Hot Pressing 조건이 $SiC_w$/2124AI 금속복합재료의 기계적 성질 및 미세구조에 미치는 영향
홍순형 한국분말야금학회 1994 한국분말재료학회지 (KPMI) Vol.1 No.2
The variation of the microstructures and the mechanical properties with varying vacuum hot pressing temperature and pressure was investigated in PyM processed 20 vol%) SiCw/ 2124Al composites. As increasing the vacuum hot pressing temperature, the aspect ratio of whiskers and density of composites increased due to the softening of 2124Al matrix with the increased amount of liquid phase. The tensile strength of composite increased with increasing vacuum hot pressing temperature up to $570^{\circ}C$ and became saturated above $570^{\circ}C$, To attain the high densification of composites above 99%, the vacuum hot pressing pressure was needed to be above 70 MPa. However, the higher vacuum hot pressing pressure above 70 MPa was not effective to increase the tensile strength due to the reduced aspect ratio of SiC whiskers from damage of whiskers during vacuum hot pressing. A phenomenological equation to predict the tensile strength of $SiC_w$/2124AI composite was proposed as a function including two microstructural parameters, i.e. density of composites and aspect ratio of whiskers. The tensile strength of $SiC_w$/2124AI were found more sensitive to the porosity than other P/M materials due to the higher stress concentration and reduced load transfer efficiency by the pores locating at whisker/matrix interfaces.
정신분열증 환자에서 Reserpine이 혈청 Prolactin 농도에 미치는 영향에 대한 연구
홍순형,서광윤,이병윤 고려대학교 의과대학 1988 고려대 의대 잡지 Vol.25 No.1
The author evaluated basal serum prolactin level and prolactin responses to reserpine in twelve schizophrenics and fourteen normal controls to assess dopamine hypothesis that postulated increased dopaminergic activity in certain brain regions of schizophrenics. In addition, twelve schizophrenics divided into paranoid type (seven) and nonparanoid type (five) to evaluate whether there is any biological differences or not among them. The results were as follows : 1. The basal serum prolactin level in the normals was 11.8+5.1ng/ml, and in the schizophrenics was 10.7+5.9ng/ml. There was no significant difference between normals and schizophrenics. 2. Prolactin response patterns to reserpine showed increased serum prolactin level in both of normals and schizophrenics, but normal group manifested higher level significantly than schizophrenics especially after 120 minutes of the reserpine injection. 3. The area under the prolactin curve was significantly different between normals and schizophrenics. Normal group had a larger prolactin response than schizophrenics (2.37: 1). 4. There was no significant difference between paranoid type and nonparanoid type in basal serum prolactin level and in prolactin responses after reserpine injection.
Nb 함유 HSLA 강의 저주기 피로실험에서 분위기의 영향 및 소성변형에너지에 관한 연구
홍순형,박종욱,이원종 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.5
The influence of plastic strain amplitude and gaseous environment on the low cycle fatigue properties has been studied in a Nb-bearing HSLA steel. The cyclic response under plastic-strain controlled loading is determined. Neither the cyclic stress-strain curve (CSSC) shows a plateau nor persistent slip bunds (PSB's) have been observed in the bulk. The cyclic plastic strain energy (ΔW) and the accumulated plastic strain energy (W) have been calculated as a function of plastic strain amplitude (Δ_(εΡ)/2) in the form of Κ(Δ_(εp)/2)^N. The computed values of ΔW and W are in good agreement with the experimental data. The vacuum environment enhances fatigue crack initiation life, fatigue life and W. The environmental effect becomes more severe as the plastic strain amplitude decreases. Tensile properties, cyclic stress response and ΔW are not affected by the gaseous environment.