논문 : 용접 및 접합 ; Al-Si-Mg-Cu-Ge 필러합금에 의한 6061알루미늄합금의 진공브레이징

이태원 ( Tae Won Lee ),이지환 ( Chi Hwan Lee ),이두면 ( Doo Myun Lee ),김종훈 ( Jong Hoon Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.6

The vacuum brazing of 6061 aluminium alloy with Al-12Si-1Mg-5Cu-xGe(x=0, 10, 20wt.%) braze alloy has been conducted at temperatures ranged 530~570℃ for 60min under brazing pressure of 1MPa to investigate the braze joint microstructure. the joint strength and the wettability of braze alloy. The liquidus temperatures of braze alloys with Ge=0, 10, 20wt.% were 572℃, 558℃ and 541℃, respectively. The wettability of braze alloy was found to be improved with increasing the brazing temperature. Braze joint microstructure was varied with the brazing temperature. Under low brazing temperatures(≤550℃, the silicon and germanium, which are expected to be the elements present in the braze alloy, are observed at the braze joint. On the other hand, these elements were not detected under the brazing temperature of 570℃. This may be due to the diffusion of the elements into 6061 aluminium alloy. The joint strength was found to be increased with increasing the brazing temperature. The maximum joint strength was obtained at 570℃ brazing temperature and its value was 73% of tensile strength of the base metal.

다이캐스팅법에 의해 제조된 SiC 입자강화 알루미늄합금기 복합재료의 미세조직 및 인장특성

이태원,이지환 ( Tae Won Lee,Chi Hwan Lee ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.4

N/A The main objective of this study is to investigate the microstructure and tensile strength of SiC_p/Al alloy composites fabricated by die casting method. Die casting was performed using the preheated mold at the pouring temperature range of 620∼750℃ under the pressure of 1,039 kgf/㎠. The low speed and a following high injection speed were 0.4 and 2.1m/s, respectively. The microstructure of SiC_p/Al alloy composites fabricated by die casting method was found to be finer than that of composites fabricated by gravity casting. Also, SiC particulates were homogeneously distributed in refined A1 matrix due to rapid solidification. The tensile strength of SiC_p/Al alloy composites fabricated by die casting method was found to be varied with cast temperature. The maximun tensile strength of SiC_p(10 vol.% and 20 vol.%)/Al alloy composites showed 380 MPa at the cast temperature of 750℃ and 363 MPa at the cast temperature of 700℃, respectively.

Effects of different levels of crude protein and protease on nitrogen utilization, nutrient digestibility, and growth performance in growing pigs

Yong Ju Kim,Tae Heon Kim,Min Ho Song,안지선,Won Yun,이지환,오한진,Jun Soeng Lee,김곡미,김현범,Jin Ho Cho 한국축산학회 2020 한국축산학회지 Vol.62 No.5

This study was conducted to evaluate the effects of different levels of crude protein (CP) and protease on nitrogen (N) utilization, nutrient digestibility, and growth performance in growing pigs. A total of six crossbred ([Landrace × Yorkshire] × Duroc) barrows were individually accepted in 1.2 m × 0.7 m × 0.96 m stainless steel metabolism cages. The pigs (average initial body weight of 27.91 ± 1.84 kg) randomly assigned to six diets with six weeks (6 × 6 Latin square design). The experiment was carried out in an environment with a temperature of 23 ± 1.5℃, a relative humidity of 83 ± 2.3% and a wind speed of 0.25 ± 0.03 m/s. The dietary treatments were arranged in a 2 × 3 factorial design with two levels of CP (15.3% or 17.1%) and three levels of protease (0 ppm, 150 ppm, or 300 ppm). The average daily gain and gain to feed ratio (G:F) tended to increase (p = 0.074) with increasing amounts of protease. The low CP level diet reduced (p < 0.050) urinary and fecal N concentrations, the total N excretion in feces, and increased (p < 0.050) N retention. Different protease levels in the diet did not affect (p > 0.05) at N intake, but supplementation of the diets with 300 ppm protease decreased (p < 0.050) the N concentration in urine and feces and tended to increase (p = 0.061) the percentage of N retention retained of the total N intake. The dietary CP level did not affect (p > 0.050) the apparent total tract digestibility (ATTD) of dry matter, digestible energy (DE), and metabolic energy (ME), but diet supplementation with 300 ppm protease showed higher (p < 0.050) ATTD of DE and ME than in the protease-free diet. Therefore, a low protein diet with protease could improve the utilization of nitrogen, thereby reducing the negative effect of N excretion into the environment while maintaining or increasing growth performance compared to a high protein diet.

열수 전처리에 따른 톨페스큐와 옥수수 사일리지의 영양적 가치와 in vitro 발효특성에 미치는 영향

김동현(Dong Hyeon Kim),손준규(Jun Kyu Son),이지환(Ji Hwan Lee),김상범(Sang Bum Kim),박범영(Beom Young Park),김두산(Doo San Kim),장길원(Gul Won Jang),임현주(Hyun Joo Lim),허태영(Tai Young Hur),김언태(Eun Tae Kim) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.1

본 연구는 열수 전처리에 따른 사료의 영양소 함량과 반추위내 발효특성의 변화를 알아보고자 수행되었다. 본 시험은 2(대조구 또는 열수 전처리)×2(건초; 톨페스큐 또는 사일리지; 옥수수)의 요인설계를 통해 실시하였다. 열수 전처리는 사료에 물을 20% w/v 수준하고, 멸균기를 이용하여 열처리를 20분간 실시하였다(121℃, 0.12 MPa). 제조된 시험사료는 in vitro 배양 시험을 통해 39℃에서 24시간 및 48시간동안 배양하였다. 연구결과, 열수 전처리 후 ADF의 함량은 조사료 종류에 구분없이 모두 유의적으로 증가하였다. In vitro 24시간 배양 후 total VFA는 조사료 종류에 관계없이 열수 전처리 후에 함량이 유의적으로 낮았으며(p ≤ 0.05), Propionate 함량은 열수 전처리된 옥수수 사일리지에서 옥수수 사일리지 보다 유의적으로 증가하였다(18.9 vs. 26.6%; p ≤ 0.05). In vitro 48시간 배양 후에는 옥수수 사일리지에서 열수 천처리에 의해 propionate 함량이 유의적으로 증가하였으나(p ≤ 0.05), Butyrate 함량은 유의적으로 감소하였다(p ≤ 0.05). 건물과 NDF 소화율의 경우에는 조사료 종류에 관계없이 열수 전처리에 의한 변화가 없었다(p > 0.05). 따라서 열수 전처리된 옥수수 사일리지를 이용할 시 반추동물의 에너지원 공급에 유리할 것으로 판단된다. This study examined the effects of a hydrothermal pretreatment (HP) on the nutritional values and in vitro fermentation characteristics of tall fescue and corn silage. This study was conducted through a factorial design of 2 (control or HP) x 2 (hay; tall fescue or silage; corn). For the HP, forage was placed into a glass bottle with 20% w/v of water, and the glass bottle was sealed and heated to reach a temperature of 121°C (0.12 MPa). The solid residue and liquid were collected and oven-dried at 65°C for three days. The dried materials were tested for in vitro fermentation at 39℃ for 24 and 48 h. The content of ADF increased significantly regardless of the forage type. After in vitro incubation for 24 h, the total VFA content was significantly lower after HP, regardless of the forage type (p ≤ 0.05), and the propionate concentration was increased in corn silage with HP (p ≤ 0.05). After 48 hours of in vitro incubation, the propionate content increased significantly (p ≤ 0.03) in corn silage with HP (p ≤ 0.05), but the butyrate content decreased significantly (p ≤ 0.05). There was no change in the in vitro dry matter and neutral detergent fiber digestibility by HP regardless of the forage type. Therefore, the use of hydrothermally pretreated corn silage could be advantageous for the supply of energy for ruminants.

알루미나와 동산화물의 공정반응층에 미치는 수소환원의 영향

이지환,이태원 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.1

The microstructural evolution and sheet resistance of copper-metallized alumina substrate have been investigated in terms of calcination temperature and hydrogen reduction temperature. The paste was made by mixing Cu₂O powder with binder. The alumina substrates were screen-printed with Cu₂O paste to 50㎛ thickness and heated at the temperature range from 1050℃ to 1200℃ for 30min in air atmosphere. The hydrogen reduction was performed at the temperature range from 200℃ to 800℃ for 30min. The calcined surface was densified at the temperature range from 1150℃ to 1200℃ due to the full melting of copper oxide powders. It was observed that the morphology of hydrogen reduced surface was more porous than that of calcined surface. Also, it was found that the morphology of hydrogen reduced surface depended upon calcination temperature. The sheet resistance value of copper-metatlized alumina substrate was varied with calcination temperature and hydrogen reduction temperature

Ti/Al 접합계면의 미세조직과 접합강도에 미치는 접합온도의 영향

이지환,이태원,김인겸 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.10

This paper was focused to investigate the effect of bonding temperature on the microstructure of Ti/Al bond interface and the bonding strength. The bonding of Ti/Al with Al-10Si-1Mg(wt.%) filler metal has been conducted at the temperature range of 560∼640℃ for 30min under bonding pressure of 0.4MPa. The liquidus temperature of filler metal was 582℃. The intermetallic compounds, such as Ti_7Al_5Si_(12), Ti_9Al_(23) and Al₃Ti, are found to be formed in the Ti/Al interface at bonding temperatures above 600℃. Dominant phase in intermetallic compound layer is Ti_7Al_5Si_(12) at 600℃ and Ti_9Al_(23) at 640℃. The thickness of intermetallic compound layer was increased with increasing bonding temperature. It was considered that the growth of intermetallic compound layer had relevance to the transformation of dominant phase in intermetallic compound layer with bonding temperature; the intermetallic compound layer tend to grow by the diffusion of silicon to aluminium-base metal from Si rich phase(Ti_7Al_5Si_(12)). This result indicated that dominant phase was transformed Ti_7Al_5Si_(12) into Ti_9Al_(23) With increasing bonding temperature through diffusion of silicon. It was found that the maximum bonding strength was 92MPa at the temperature of 600℃.

알루미늄합금기 주조복합재료의 인장특성에 미치는 다이캐스팅온도의 영향

이지환,이태원 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.7

This study was focused to investigate the influence of die casting temperature on microstructure and mechanical properties of SiC_p(10 and 20vol%)/Al alloy composites and to perform statistical evaluation for strength of SiC_p/Al alloy composites in order to predict the die cast Al alloy composites reliability. Die casting was performed using the preheated mold at the pouring temperature range of 620-750℃ under the pressure of 1,039㎏f/㎠. The pre-charging low speed and a following high injection speed were 0.4 and 2.1㎧, respectively. It was found that the SiC particulates were homogeneously distributed in refined Al matrix, resulting from the improvement of segregation due to rapid solidification. The tensile strength of SiC_p(10 and 20vol%)/Al alloy composites was found to be increased with increasing cast temperature. However, the tensile strength was decreased at the cast temperature of 750℃ in 20vol%/Al alloy composites. For the statistical evaluation of strength, the weibull modulus of SiC_p/Al composites was 22.2(10vol.%) and 14.2(20vol%) at cast temperature of 700℃.

확산접합한 Ti/Al 접합체의 미세조직과 접합강도

이지환,이태원,김인겸 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.4

The main objective of this study is to investigate the bonding strength and the microstructure of Ti/Al joints bonded by diffusion bonding method. The bonding of Ti/A1 was performed at the temperature range of 560-630℃ for 3-300min under bonding pressure of 1㎫ in vacuum atmosphere. The intermetallic compound, Al₃Ti, was found to be formed into the titanium side at the Ti/Al interface. The thickness of Al₃Ti layer was increased almost linearly with increasing bonding time up to about 10㎛. Bonding strength increased with increasing bonding time up to 60min at 600℃ The thickness of Al₃Ti layer was about 4㎛ at 600℃/60min. However, bonding strength showed a equal value(100㎫) at the bonding time range of 60-300min at 600℃. The Ti/Al joints were fractured at the interface of Al/Al₃Ti layer in all bonding conditions, no fracture was observed in Al₃Ti layer. Particularly, the Ti/Al joints bonded for more than 60min at 600℃ were fractured at the aluminium base metal. Therefore, it is considered that bonding strength was not dependent upon thickness of Al₃Ti layer(4-10㎛) because of Ti/Al joints were fractured at the interface of Al/Al₃Ti layer regardless of Al₃Ti layer thickness.

NiAl 계 금속간화합물의 반응합성에 미치는 성형조건 및 승온속도의 영향

이지환,이태원 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.11

다이캐스팅한 SiC p/Al 합금기 복합재료의 미세조직과 기계적성질

이태원,서병권,이두면,이지환 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.3

This study was focused to investigate the effect of die casting on the microstructure and mechanical properties of SiC_p(10 and 20vol.%)/Al alloy composites. Die casting was performed using the preheated mold at the pouring temperature of 650∼700℃ under the pressure of 916 ㎏f/㎠. The speeds of slow and high speed injection were 0.3∼0.4 and 1.4 m/s, respectively. It was found that the SiC particles were homogeneously distributed in refined Al matrix. This results from the rapid mixing of molten Al and SiC particles during injection and the improvement of segregation due to rapid solidification. Therefore, the tensile strength of SiC_p/Al alloy composites die cast at 700℃ appeared to be superior to that of the composites die cast at 650℃ with 10 and 20 volume fractions.