Al-7%Si-0.3%Mg 合金의 衝擊靭性에 미치는 Zn添加의 影響에 관한 硏究

尹義博,金永稷 成均館大學校 1981 論文集 Vol.29 No.-

熱處理, Sb添加條件, Zn含量이 機械的 性質에 미치는 영향에 대해 조사하였다. 共晶Si의 크기와 형태는 적절한 熱處理에 依해 微細·球狀化하였다. 760℃에서 Al-7%Si合金에 0.15%Sb를 添加함으로써 共晶Si의 改良處理가 되었으며, 그 後 0.3%Mg를 添加시키면 强度와 伸率은 向上되었다. 356合金에 Zn이 0.2%에서 2.0%까지 添加되면 引張强度, 降伏强度는 增加하나 伸率은 오히려 減少하는 데, 이것은 Mg_2Si및 Zn_2Mg相이 粒界 및 粒內에 석출되기 때문이라고 생각된다. 또, 흡수에너지는 1.3%Zn까지는 급격히 減少하나, 그 以上에서는 거의 一定하게 되었다. Effects of heat treatment, addition of Sb, and Zn contents on the mechanical properties were examined. The size and shape of eutectic-Si particles is refined and spherodized by the optimum heat treatment. Adding of 0.15% Sb to the Al-7% Si alloy at 760℃, it is obtained modification of eutectic-Si particles, and moreover addition of 0.3% Mg contributes to promote strength and ductility. When the Zn content in increases up to 2% in Al-7%Si-0.3%Mg alloy, ultimate and yield strength increases, while ductility decreases because of precipitation of Mg_2Si, Zn_2Mg in matrix and between grain boundaries. The toughness (absorbed energy) decreases rapidly up 1.3% Zn, but become-nearly constant above 1.3% Zn.

Al合金의 Micro 偏析에 관하여

尹義博 成均館大學校 1980 論文集 Vol.27 No.-

The influence of solidification conditions on microsegregation of dendritic structures was investigated with unidirectionally solidified Al-Cu alloy. In order to study the result of microsegregation, solute distribution at each distance from the chill surface was determind as a function of the fraction of solid which was given by two dimensional solidification model. Also the mechanism of solute redistribution during the growth of dendrite was discussed. The segregation index (S) increased by decreasing the solidification rate (R), and the S between primary dendrite arms was more remarkable than that between secondary dendrite arms. The relationship between S and R was generally obtained as follows; S=A log R+C where, A and C are the constants determined by concentration. Cu-isoconcentration curves around the dendrite element demonstrated Cu concentration to be minimum at the center of primary dendrite stalk. With decreasing distance from the chill surface (increasing R) the effective partition coefficient Ke (also minimum Cu concentration) increased, but Ke was little affected by concentration. The relationship between Ke and R was obtained as follows; Ke=0.21 log R+0.2 in which, R is cm/min. The influence of diffusion layer on the solute movement ahead of the solid-liquid interface near the dendrite tip which was not obtained by means of the prior linear analysis in Al-Cu alloys was clearly demonstrated by determining the fraction of solid from two dimensional solidification model, and it was found that the diffusion layer has a remarkable effect upon the solute redistribution. The degree of microsegregation was dependent upon the change of the effective partition coefficient with the change in the rate of solidification, and could be interpreted qualitatively by the partially mixed liquid model.

Al-Cu合金의 凝固組織에 관한 硏究

尹義博 成均館大學校 1980 論文集 Vol.27 No.-

Primary and secondary dendrite arm spacing increases with decreasing average cooling velocity. But primary arm spacing increases with Cu content, while secondary arm spacing does not change appreciably with Cu content over the composition range investigated. The relationships between these were obtained as follows; λ_1=0.87√Co/Va, λ_2=177Va^-1/3 wehre, λ_1 is the primary arm spacing (mm), Co is the Cu content (%), Va the average cooling velocity (℃/min) and λ_2 the secondary arm spacing (μ). As the solidification rate increases, the size and mean free path of the θ phase show an appreciable decrease. And mean free path between θ-partcles is similar to the order of the secondary dendrite arm spacing. With decreasing distance from the chill face (that is, increasing solidification rate), the amount of θ phase decreases over the range of solidification conditions investigated in this paper. As distance from chill becomes smaller, lattice constant decreases, and the Cu-content in α-matrix increased. From these results. The behavior of second phase in unidirectionally soildified Al-Cu alloys could be confirmed quantitatively.

二相 混合 組織을 가진 球狀黑鉛鑄鐵의 靭性에 미치는 熱處理의 影響

尹義博,李相鶴 成均館大學校 1981 論文集 Vol.29 No.-

本 論文은 Ferrite 球狀黑鉛鑄鐵을 利用하여 第二相의 上部 Bainite와 下部 Bainite 等의 混合量을 廣範圍하게 變化시켜 鑄鐵의 機械的 特性을 向上시키는 데 그 目的이 있다. ① 0.2% 耐力, 引張强度 및 硬度는 第二相 變態量의 增加와 더불어 上昇하였으나 直線的으로는 上昇하지 않았다. 또한 第二相이 强하면 强할수록 引張强度는 더욱 높았다. ② 伸率 및 흡수에너지는 變態量이 20∼30%정도 까지는 急激하게 低下하지만 그 以上에서는 완만하게 低下함을 알았다. ③ 球狀黑鉛鑄鐵의 勒性은 Ferrite地 組織에 적절한 第二相을 적당량 混合함으로써 改善됨을 알았다. The object of this paper is to improve the mechanical properties spheroidal graphite cast iron by duplex matrix which is used in steel alloys. Ferrite spheroidal graphite case iron is heat-treated to produce the following duplex matrices with various proportions; Ferrite-upper bainite, Ferrite-low bainite etc. 0.2% proof stress, tensile strength and hardness increase with volume fraction of the second phase, but are no linearly shown as the law of mixture. The harder the second phase is, the higher the strength becomes. The elongation value and absorbed energy decrease rapidly with in 20-30% of volume fraction of the second phase, but decrease slowly in above 20-30% of volume fraction of the second phase. The toughness of spheroidal graphite case lron can be improved by proper volume fraction of the proper second phase in ferrite structure.

비평형제2상의 용체화거동에 미치는 응고조직의 영향

윤의박,안갑우,서창제,허태수 대한금속재료학회(대한금속학회) 1980 대한금속·재료학회지 Vol.18 No.5

偏析型 2元系合金의 溶體化末期에 있어서 非平衡第2相의 固溶擧動에 대해서는 아직까지 理論的으로 정립되어 있지 않았다. 本 論文에서는 主로 dendrite element의 境界에 晶出된 非平衡第2相의 유효擴散距離로써 1次arm 間隔을 考慮한 擴散 model인 尹의 近似解에 의해 이들 擧動을 調査하였다. 이를 위해 天然가스등의 輸送材料로 囑望되는 高濃度 Al-8%Mg合金을 사용하였다. 實驗結果, 理論的인 尹의 近似解의 實驗値는 近似的으로 一致되었고, 특히 溶體化末期에서는 完全히 一致됨을 알 수 있다. 結局 從來의 Flemings의 解析値보다 더욱 實驗値에 近似하였다. The solution kinetics of nonequilibrium second phase of a segregated binary alloy in the later stages of solution treatment have not yet been made theoretically clear. This paper attempted mainly to investigate this behaviour by Yoon's approximate analysis given by a simple model based upon primary arm spacing as an effective diffusion distance of the second phase which has crystallized at the boundary of dendrite element. For this purpose, we used the high magnesium Al-8% Mg alloy which is expected to be used for transport of liguified natural gas. The theoretically calculated results are in the approximate agreement with that of experiments for complete dissolution time and solution kinetics (expecially at the later stages) of β-phase. The Yoon's approximate analysis was in better agreement with the present experimental results than the Flemings conventional analysis

원자로압력용기장 용접열영향부의 미세조직 변화가 Magnetic Barkhausen Noise 거동에 미치는 영향

김주학,윤의박,문종걸,박덕근,홍준화 韓國非破壞檢査學會 1998 한국비파괴검사학회지 Vol.18 No.4

최근 자기적 특성의 변화가 재료의 미세조직적 상태에 민감하다는 보고가 있다. 재료의 미세조직은 상(phase), 결정립의 크기, 석출물 등의 다양한 인자로 구성되며, 본 연구에서는 이러한 인자들을 이용하여 재료의 특성과 Barkhausen noise(BN)의 관계를 연관시키기 위한 시도를 하였다. ASTM A 508 Gr.3 원자로압력용기강을 대상으로 용접열영향부의 미세조직적인 변화를 일곱가지 대표적인 영역으로 구분하였고, 각 영역에서의 미세조직과 기계적특성의 변화를 파악한 후, 각 조건별로 BN을 측정하였다. 통상의 보자력이나 잔류자화 같은 자기적 성질은 큰 변화가 없었지만, BN은 미세조직의 상태에 따라 현격한 변화를 보였다. 결정립과 석출물의 크기가 증가함에 따라 BN은 증가하였고, tempered martensite 보다는 tempered bainite 조직에서 높은 BN을 나타냈다. Recent study has demonstrated that some magnetic properties are sensitive to the microstructural state of material. The ASTM A 508 Gr. 3 reactor pressure vessel steel has various microstructural changes including martensitic and bainitic phases, and various sizes of grain and precipitates in the weld heat-affected zone (HAZ). To correlate the microstructural state with Barkhausen noise (BN), specimens were prepared through simulating various weld thermal cycles using a thermal simulator. The conventional magnetic properties, i.e. coercive force, remanence and maximum induction, did not change significantly. whereas the BN amplitude and energy during a magnetization cycle changed markedly with microstructural state. The BN increased with increasing grain and carbide sizes, and the tempered bainite structure showed higher BN parameter than tempered martensite.

INFLUENCE OF THE SEGREGATION OF IMPURITIES ON REFINING FOR Al - RECYCLYING

Eui Pak Yoon,Yeon Wook Kim 대한금속재료학회 ( 구 대한금속학회 ) 1992 Advanced Material and Processing Vol.- No.-

전자기력을 이용한 알루미늄 합금중 개재물의 연속적 제거에 관한 연구

윤의박(Eui Pak Yoon) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.3

N/A The growing use of aluminum for castings over the past decade has brought with it the increased scrutiny of component properties. One area that has received much attention is the effect of in inclusions - or impurities particles held in the metal - on casting properties. A new method of electromagnetic separation for removal of inclusions in aluminum alloy melts is proposed. The principle is that as the electromagnetic force induced in metal acts on inclusions due to low electric conductivity, they are moved to the direction opposite to electromagnetic force and can be separated and removed from the melt. Experiments were carried out on A356 melt mixed alumina particles and commercial Al alloys of ADC 10 and 12. In the experiment using A356, it was proved that Al-2O_3 particles was separated and removed continuously from matrix melt by electromagnetic force. Based on these results, the continuous separation experiment that used ADC 10, 12 was carried and the cleanliness of melt was assessed by the amount of porosity, hydrogen contents, PoDFA and mechanical properties through tensile test. As the results of analyses, the amount of porosity and hydrogen contents decreased without variation of chemical composition in the specimen that passed the electromagnetic continuous separator. In addition, tensile strength and elongation of this specimen increased by 20∼30% because of reduction of inclusions.

Mg 합금주물의 전망

윤의박 ( Eui Pak Yoon ) 한국주조공학회 1987 한국주조공학회지 Vol.7 No.1

Effects of Alloying Elements on Fracture Properties of Niobium Stabilized Austenitic Steels at Elevated Temperature

Yoon, Ji Hyun,Yoon, Eui Pak,Lee, Bong Sang Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.345-346 No.-

<P>The present work is a further investigation into the effects of the carbon (C), nitrogen (N) and niobium (Nb) contents on then fracture properties of the Type 347 stainless steels at 316oC. 9 heats of systematically designed alloys were examined. Through SEM-EDS, TEM and XRD analyses, two kinds of precipitates, Nb(C,N), CrNbN were identified in the Type 347 steels with a high ratio of wt% N to wt% C, on the other hand only Nb(C,N)s were found in the Type 347 steels with a low ratio of wt% N to wt% C. The tearing moduli were decreased in the range of 52~60% as the carbon content increased from 0.03wt% to 0.05wt%. The tearing moduli were lowered by 52~59% in the alloys with a high nitrogen. It was deduced from the microstructure analysis results that the coarse Nb-rich precipitates control the fracture resistance of the Type 347 as they act as the potential sites for the nucleation of micro-voids.</P>