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A 6061 합금의 기계적 특성에 미치는 2단시효의 영향
이보배 ( Bo-bae Lee ),임항준 ( Hang-joon Im ),정걸채 ( Geol-chae Jeong ) 한국열처리공학회 2019 熱處理工學會誌 Vol.32 No.2
The impact of two-step treatment on the mechanical properties of the 6061 Al alloy was investigated by testing the hardness and electrical conductance values. After two-step aging treatment, the hardness and electrical conductivity of the alloy was increased, and if the first aging treatment temperature was lower than the secondary aging treatment temperature, both the hardness and the electrical conductivity were not increased. The higher the temperature of the first aging treatment, the higher the hardness. The temperature of the first aging treatment is 175℃, 150℃, 120℃, and the second is 175℃ and 120℃. (Received January 15, 2019; Revised January 17, 2019; Accepted January 21, 2019)
Al-Zn-Mg-Cu계 알루미늄 합금의 열간 균열 특성에 미치는 합금조성의 영향
김지훈 ( Jee Hun Kim ),조재섭 ( Jae Sub Jo ),심우정 ( Woo Jeong Sim ),임항준 ( Hang Joon Im ) 대한금속재료학회(구 대한금속학회) 2012 대한금속·재료학회지 Vol.50 No.9
Hot tearing was the most significant casting defect when the castability evaluation of the Al- Zn-Mg-Cu alloy system was conducted. It was related to the solidification range of the alloy. Therefore, the hot tear susceptibility of the AA7075 alloy, whose solidification range is the widest, was evaluated. The hot tear susceptibility was evaluated by using a mold for a hot tearing test designed to create the condition for the occurrence of hot tear in 8 steps. According to the tearing location and shape, a hot tear susceptibility index (HTS) score was measured. The solidification range of each alloy and hot tear susceptibility was compared and thereafter the microstructure of a near tear defect was observed. As a result, the HTS of the AA7075 alloy was found to be 67. Also, the HTS in relation to a change in Zn, Mg, Cu composition showed a difference of about 6-11% compared to the AA7075 alloy.
Al-Zn-Mg계 알루미늄 합금의 유동성에 미치는 합금원소의 영향
조재섭 ( Jea Sup Cho ),김지훈 ( Jee Hun Kim ),심우정 ( Woo Jeong Kim ),임항준 ( Hang Joon Im ) 한국주조공학회 2012 한국주조공학회지 Vol.32 No.3
Al-Zn-Mg alloys, being high strength aluminum alloys, have attracted attention as a material of automobile parts that require higher mechanical properties and lightness. Automobile parts with complex shapes are manufactured by low-priced casting method, but Al-Zn-Mg alloys are difficult to cast because of its poor hot cracking, feeding, and fluidity. Thus fluidity experiments on Al-Zn-Mg alloys were conducted for the castability evaluation. The effects of Mg and Zn, representative elements of Al-Zn-Mg alloys, on fluidity were observed. Spiral mold was used for fluidity experiments and the lengths of solidified specimens were measured after melting and gravity casting. Correlation between microstructures and fluidity length based on the alloy composition was considered. According to the experimental results, as the amount of Mg and Zn increased, fluidity decreased. Also, it was confirmed that fluidity change by the variation of Mg composition was greater than that of Zn.
반응소결 탄화규소의 다양한 α-SiC 조성에 따른 기계적 특성과 전기저항 특성에 관한 연구
김영주 ( Young Ju Kim ),박영식 ( Young Shik Park ),정연웅 ( Youn Woong Jung ),송준백 ( Jun Baek Song ),박소영 ( So Young Park ),임항준 ( Hang Joon Im ) 한국복합재료학회 2012 Composites research Vol.25 No.6
저저항 Si-SiC 소결체 제조를 위해 α-SiC에서 조성과 C의 양을 변화시키면서 반응소결 특성을 고찰하였다. 시료준비는 정수압으로 성형체를 제조하였고, 용융Si 반응소결을 통해 시험편을 준비하였다. 반응소결체의 미세구조, 기계적 특성 및 전기 저항 분석 결과 용융Si과 반응 후 미립의 β-SiC가 생성되었고, 치밀한 소결체를 형성하였다. 미립 β-SiC 생성량은 카본 양 에 따라 증가하였다. 그리고 C함량 10wt%이내에서 기계·R전기저항특성은 입도조성 영향이 크고 카본 함량 10wt%이상에서는 상전이 반응의 영향이 큼을 알 수 있었다. For the manufacture of low resistance Si-SiC composite, the properties of reaction sintering in the green body of various mixed α-SiC powder size with the various carbon contents from 0wt% to 20wt% were investigated. The samples preparation was green body by CIP method under this condition, molten silicon infiltration process was conducted to reaction bonded silicon carbide. the results of sintered density, 3-point bending strength and resistance of analysis showed that varied carbon and silicon melt reacted to convert to fine β-SiC particle and the structure was changed to dense material. The amount of fine β-SiC particle was gradually increased as carbon content increase. According to mixed composite, it``s mechanical and specific resistivity properties was strongly influenced by carbon content within 10wt% more then carbon content 10wt% was strongly influenced by phase transition.