주조 및 불연속 석출물 미세조직을 가지는 Mg-Al 합금의 진동감쇠능

전중환,Jun, Joong-Hwan 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.5

In this study, damping capacities were comparatively investigated for Mg-9%Al alloy with as-cast (AC) and fully discontinuous precipitates (DPs) microstructures, respectively. The DPs microstructure was obtained by solution treatment at 678 K for 24 h, followed by furnace cooling to RT. The AC microstructure was typically characterized by partially divorced eutectic β(Mg₁₇Al₁₂) phase particles distributed along the α-(Mg) matrix cell boundaries. The DPs microstructure showed lamellar morphology consisting of α and β thin layers with various interlamellar spacings. The DPs microstructure had better damping capacity than the AC microstructure in the strain-amplitude independent region, while in the strain-amplitude dependent region, the damping behavior was reversed. In view of the microstructural features of AC and DPs, the lower concentration of Al in the α-(Mg) phase for the DPs microstructure and the lower β phase number density for the AC microstructure would be responsible for the higher damping capacities in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

동물복지 관련 산란계 농가 실태조사

전중환,이준엽,박규현,김두환,송준익,Jeon, Jung-Hwan,Lee, Jun-Yeob,Park, Kyu-Hyun,Kim, Doo-Hwan,Song, Jun-Ik 한국축산환경학회 2012 축산시설환경학회지 Vol.18 No.3

본 조사는 산란계 케이지 사육시설에 대한 대체 사육시설 등 해결방안을 모색하기 위한 기초자료를 확보하기 위하여 평사, 방사사육 및 동물복지 사육시설을 사용하는 산란계 농가를 대상으로 사육시설에 대한 실태를 조사하였다. 사육형태는 방사사육, 평사사육 및 대체 사육시설 3가지로 구분되었으며, 축사형태는 무창축사와 개방축사 2가지로 구분할 수 있었다. 급이기는 선형과 원형이 각 37.5%와 62.5%로 조사되었으며, 급수기는 니플이 75%, 선형이 12.5%, 버켓이 12.5%로 조사되었다. 사육밀도의 경우 평균 5.6수/$m^2$로 조사한 모든 농가가 인증기준에 부합하였다. 횃대가 설치되어 있지 않은 곳이 25%에 달하였으며 횃대가 설치되어 있는 농가의 경우도 수당 15 cm 이상의 횃대가 제공되어야 하는 인증기준에 미달하는 것으로 조사되었다. 또한 전체 조사농가의 50%가 재래식 산란상을 사용하고 있으며 이로 인하여 인력수거 방식으로 집란하고 있었다. Studies of non-cage or alternative systems have been discussing in EU because the EU has banned use of conventional cages for laying hens since 2012. This survey was carried out the information related to laying hens' welfare in Korea. Laying hens' breeding systems divided into deep litter, free range and alternative system, and livestock housings divided into windowless housing and open-type housing. The ratios of trough and bell feeder types were 37.5% and 62.5%, respectively. The ratios of nipple, trough, and bucket in waterer types 75%, 12.5%, and 12.5%, respectively. What stocking density is the most appropriate for production and welfare has been aroused. All laying hen farms met the required standards of stocking density ranged from 3.4 birds/$m^2$ to 7.6 birds/$m^2$ in this survey. According to welfare standards for laying hens, perch length should not be less than 15 cm. However, most laying hen farms did not satisfied the standards. We believe that presentdata contribute to develop alternative systems and to improve animal welfare in Korea.

Fe-17%Mn 합금의 진동감쇠능에 미치는 ε 마르텐사이트 함량과 진폭변형율의 영향

전중환,이영국,최종술 ( Joong Hwan Jun,Young Kook Lee,Chong Sool Choi ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.2

The effects of ε martensite content and strain amplitude on damping capacity of an Fe-17%Mn alloy have been studied to establish damping mechanism of Fe-Mn system corresponding to the magnitude of strain amplitude. In a range of 1×10^(-4)∼3×10^(-4) strain amplitude, the damping capacity is linearly proportional to the ε martensite content, which suggests that stacking faults and ε martensite variant boundaries are the principal damping sources. In the range of 4×10^(-4)∼6×10^(-4) strain amplitude, however, a maximum damping capacity is observed around 68 vol% ε. This behavior is very similar to dependence of relative area of γ/ε interface on ε martensite content. This means that in this strain range, γ/ε interface acts as damping source in addition to the stacking faults and variant boundaries in Fe-17%Mn alloy.

용체화처리된 Mg-4%Zn 합금의 부식 저항성에 미치는 미량 Ca 첨가의 영향

전중환,황인제,Jun, Joong-Hwan,Hwang, In-Je 한국열처리공학회 2016 熱處理工學會誌 Vol.29 No.4

Influence of trace amount of Ca addition on the corrosion resistance was comparatively investigated in solutionized Mg-4%Zn and Mg-4%Zn-0.1%Ca alloys. In as-cast state, the alloys were characterized by primary ${\alpha}-(Mg)$ dendrite with MgZn intermetallic compound particles. After solution-treatment, both alloys consisted of single ${\alpha}-(Mg)$ phase by dissolution of the compound particles into the matrix. It was found from the immersion and electrochemical corrosion tests that the Mg-4%Zn alloy had better corrosion resistance than the Mg-4%Zn-0.1%Ca alloy. Morphological and compositional analyses on the surface corrosion products indicate that the incorporation of Ca oxide with low PBR value into the surface corrosion products would be responsible for the decreased corrosion resistance of the Ca-containing alloy.

마그네슘의 진동감쇠능에 미치는 냉각 속도의 영향

전중환,Jun, Joong-Hwan 한국열처리공학회 2017 熱處理工學會誌 Vol.30 No.6

The effect of cooling rate on the damping capacity of pure Mg was studied. Two Mg samples with different cooling rates were prepared by heat treatment at 873 K for 24 h, followed by water quenching and by furnace cooling to room temperature, respectively. The average grain sizes of the Mg samples were almost identical regardless of the cooling rate, but more twins were observed in the sample with faster cooling rate. The calculated vacancy fraction was higher in the fast cooling sample than the slow cooling one. It is noted that the fast cooling sample exhibited lower damping capacity both in the strain-amplitude independent and strain-amplitude dependent regions. Higher values of vacancy concentration and number density of twins in the fast cooling sample are considered to be responsible for the deteriorated damping capacity in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

Mg-Al-Zn 합금에서 불연속 석출물의 층상 구조와 경도에 미치는 냉각 속도의 영향

전중환,Jun, Joong-Hwan 한국열처리공학회 2020 熱處理工學會誌 Vol.33 No.6

The relationship between the hardness and interlamellar spacing of discontinuous precipitates (DPs) formed by continuous cooling was studied for Mg-9%Al-1%Zn alloy. After solution treatment at 683 K for 24 h, the specimens were cooled to room temperature with different cooling rates ranging from 0.2 to 2 K·min^-1, in order to obtain DPs with various interlamellar spacings. It was found that cooling rate of 2 K·min^-1 yielded only small amount of nodular DPs at the grain boundaries, while cooling rates below 2 K·min^-1 yielded both DPs and continuous precipitates (CPs). The volume fraction of DPs increased with increasing cooling rate up to 0.5 K·min^-1, over which it abruptly decreased. The hardness of DPs was increased with an increase in the cooling rate, whereas the interlamellar spacing of the DPs was decreased with respect to cooling rate. The hardness of the DPs formed by continuous cooling was correlated with the interlamellar spacing and can follow a Hall-Petch type relation as in the case of pearlite with lamellar morphology.

양돈농가의 분만돈방 및 분만틀 사용 실태조사

전중환,송준익,전병수,정의수,최희철,강희설,김두환,Jeon, Jung-Hwan,Song, Jun-Ik,Jeon, Byoung-Soo,Chung, Eui-Soo,Choi, Hee-Chul,Kang, Hee-Seol,Kim, Doo-Hwan 한국축산환경학회 2010 축산시설환경학회지 Vol.16 No.2

본 실태조사는 분만돈방과 분만틀 사용실태를 조사함으로써 분만돈의 동물복지 수준을 향상시킬 수 있는 대체 사육시설을 개발하는데 필요한 기초자료를 확보하기 위해 실시되었다. 분만돈방은 크게 형태별로 수직형 분만돈방과 사선형 분만돈방 두 가지로 구분되었으며, 분만틀은 압사방지 바(Bar)의 형태를 기준으로 수평형(Horizontal bar) 분만틀, 수직형(Vertical bar) 분만틀로 구분되었다. 기타 시설물에 대한 조사결과, 조사농가의 전체가 니플형 급수시설을 사용하고 있었으며, 약 80%가 습식급이기를 사용하고 있었고, 조사 농가의 약 40%가 전체틈바닥, 약 60%가 부분 틈바닥이었으며, 분만돈 두당 최소 $3.9\;m^2$ 이상의 면적을 제공하고 있었다. 국내의 다양한 사육시설과 환경으로 인하여 일괄적인 구조개선이나 새로운 사육시설의 적용은 쉽지 않을 것으로 판단되지만 이러한 국내 양돈농가의 실태조사 자료들을 동물복지 수준을 향상시킬 수 있는 대체 사육시설을 개발하는데 좋은 기초자료가 될 것이라 생각한다. This survey was carried out to investigate the dimensions of farrowing accommodation and farrowing crate by types. Farrowing crates are used to prevent the crushing death in the swine industry generally but farrowing crates include many problems in the animal welfare viewpoint: e.g. restriction of movements and maternal instincts. Therefore, the studies of alternative systems have been discussed for a while in U.K., U.S.A. and Canada. We surveyed eight farms for about eight months. To accurately compare the farrowing housing, small scale swine farms (3,000hd or less) were excluded from all data in this survey. Lactating accommodations were divided into vertical lactating accommodation type and diagonal accommodation type, and farrowing crates were divided into vertical bar type and horizontal bar type. In this survey, nipple waterer, partial slotted floor and total slotted floor were 80%, 40% and 60% respectively, and the lactating accommodations' dimensions ranged from 3.90 to $4.92\;m^2$. We believe that these data of the survey contribute to develop alternative systems and then contribute to improve the animal welfare in Korea.

Fe-Mn 합금에서 γ→ε마르텐사이트 변태의 Ms온도에 미치는 오스테나이트 결정립크기의 영향

전중환,최종술 ( Joong Hwan Jun,Chong Sool Choi ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.2

Effect of sustenite grain size on starting temperature of γ→ε martensitic transformation(M_s) has been studied in an Fe-18%Mn alloy. Particular attention was paid on the variation of stacking fault energy with austenite grain size, which is considered to be a important factor affecting γ→ε martensitic transformation. Austenite grain size was increased in a wide range from 13,um to 185 with increasing solution treatment temperature from 700℃ to 1100℃. Hardness was decreased with increasing austenite grain size while the volume fraction of a martensite showed a reverse tendency, which indicates that the hardness is more dependent on austenite grain size thane martensite content. No significant change was found in M_s temperature when the grain size was larger than about 30㎛. In case that, the austenite grain size was smaller than about 30㎛, however, M_s temperature was marlkedly decreased with decreasing austenite grain size. A linear relationship between M_s temperature and the stacking fault formation probability, i.e. the reciprocal of the stacking fault energy was obtained, which suggests that the variation of M_s temperature with austenite grain size is closely related to the change in stacking fault energy.

AZ91-CaO 합금의 미세조직과 인장 특성에 미치는 열처리의 영향

전중환 ( Joong Hwan Jun ) 한국열처리공학회 2012 熱處理工學會誌 Vol.25 No.4

This study aims to investigate and compare the microstructures and room temperature tensile properties for AZ91 and ECO-AZ91(AZ91+0.3%CaO) alloys in as-cast, T4 and T6 states, respectively. In as-cast state, the ECO-AZ91 alloy has finer microstructure than the AZ91 alloy. The AZ91 alloy exhibits greater ductility, while YS and UTS are inferior to those of the ECO-AZ91 alloy. After T4 treatment, most of b compounds disappear in the AZ91 alloy, whereas b phase is still observed in the ECO-AZ91 alloy due to its enhanced thermal stability, resulting in lower values of ductility and UTS. In T6 state, YS and UTS are better in the ECO-AZ91 alloy.

Mg-Al 합금에서 연속 냉각 및 등온 시효로 생성된 불연속 석출물의 미세조직 특징과 경도

전중환 ( Joong-hwan Jun ) 한국열처리공학회 2020 熱處理工學會誌 Vol.33 No.4

The purpose of this study was to investigate comparatively the microstructural characteristics and hardness of discontinuous precipitates (DPs) in Mg-9%Al alloy, which were formed by continuous cooling (CC) from 678 K to RT and isothermal aging (IA) at 413 K, respectively. In as-cast state, the Mg-9%Al alloy consisted of partially divorced eutectic β(Mg₁₇Al₁₂) particles with a small amount of DPs showing (α+β) lamellar morphology adjacent to the β particles. The DPs formed by CC had interlamellar spacings in a broad range of 0.85~2.12 ㎛ (1.51 ㎛ in average) owing to the various formation temperatures in response to continuous cooling process. Meanwhile, the DPs formed by IA had relatively narrower interlamellar spacings of 0.14~0.29 ㎛ (0.21 ㎛ in average), which is associated with the low and constant formation temperature. Thinner and higher volume fraction of β phase layers were noticeable in the DPs formed by IA. Higher hardness values were obtained in the DPs formed by IA than the DPs formed by CC, which may well be ascribed to the finer lamellar structure and higher β phase content of the DPs formed by IA. (Received June 15, 2020; Revised June 23, 2020; Accepted June 29, 2020)