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Friction stir welding for high-strength AA7075-T6 rolled sheets
Wahid Muhamad Furkon,김강석,이광진 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.11
Friction Stir Welding (FSW) had been conducted to butt-joint the AA7075-T6 rolled sheets with various rotational speed and travelling speed ranging from 800 to 1200 revolutions per minute (RPM) and 50 to 250 millimeters per minute (mm/min), respectively. The joining defects were observed on the external regions (e.g. flash, cracks, and tunnel cavities) and in the internal regions (e.g. voids, cracks). Moreover, tensile test, hardness test, and impact test were performed to determine the mechanical properties of the joints. Among those FSW conditions, the heat-process windows were established for each of the examination results. Therefore, the optimum FSW conditions were chosen based on the best for all examination results. The further investigation has been proceed by post-weld heat treatment (PWHT) the joints with the optimum FSW condition. It was found that the ultimate tensile strength of as-welded specimen was similar to the as-PWHT specimens. Additionally, the similar “W”-pattern of hardness distributions were observed between as-welded and as-PWHT.
Study on Microstructure and Mechanical Properties of Laser Welded AlMg7 Alloy Thin Sheets
Wahid Muhamad Furkon,이광진 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
Laser welding has been used commonly for welding aluminum alloys in the various industry, because a low localized heat input and high welding speeds can be produced with small distortion of welded assemblies. In this study, non-heat-treatable alloys of AlMg7 thin sheets were laser-welded with various welding powers of 1.50, 1.75, and 2.00 kW and travelling speeds of 8, 9, 10, and 11 mpm. The cross-sectional observation on these various lap joints were conducted using optical microscope (OM) and electron back-scatter diffraction (EBSD) in order to investigate the microstructures including the melting pool, heat affected zone (HAZ), and base metals (BM) regions. The tensile test was performed to evaluate the mechanical properties of lap-joints of AlMg7 thin sheets and find the optimum welding conditions. The sound joints with high tensile strength have been affected with their microstructures after laser welding will be elaborated in detail.
Wahid Muhamad Furkon,문상돈,강성욱,김재황,이광진 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
Friction Stir Welding (FSW) has been used recently to improve the weld-ability and productivity on aluminum alloys compared to the fusion welding process. Although the FSW process can avoid the defect and porosity formation, the softening on friction stir welded-joints affects the mechanical properties. A heat-treatment after friction stir welding, known as post-weld heat treatment (PWHT), can improve the mechanical properties especially on the heat-treatable alloys by precipitation hardening mechanisms. In this study, the FSW T-joint of AA6063 extrusion plates were prepared with 1000, 1200, and 1400 of rotational speeds and 40, 60, and 80 mm/min. of travelling speeds. Furthermore, PWHT was conducted at 150°C with various holding times such as 6h, 12h, 18h, 24h, and 30h. Base metal (BM), heat-affected zone (HAZ), thermo-mechanically affected zone (TMAZ), and stir zone (SZ) regions were observed under optical microscope (OM), field emission - scanning electron microscope (FE-SEM) and high-resolution transmission electron microscope (HR-TEM). Tensile tests and hardness tests were performed to evaluate the mechanical properties of T-joints.
진광혁,Wahid Muhamad Furkon,이광진 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
마찰교반용접(Friction Stir Welding)은 1991년 영국의 TWI(The Welding Institute)에 의해 개발된 이래 다양한 소재에 적용되어 왔으며, 항공기, 자동차 및 철도차량에의 적용을 목적으로 알루미늄합금과 같은 저융점 경량소재에 대한 연구가 활발히 진행되어 왔다. 최근, 국내에서는 전기구동 차량의 컨트롤러, 인버터, 배터리 및 공조 시스템 부품에 적용하고자 인장강도 300MPa 급의 중강도 알루미늄합금인 6xxx계열의 압연 판재, 압출 및 다이캐스팅 형재의 박판재에 대한 연구가 활발히 진행되고 있다. 향후, 우주항공 분야에의 적용 및 자동차 부품의 경량화, 고강도화를 위하여 인장강도 500MPa 급의 고강도 알루미늄합금에 대한 마찰교반용접 공정기술이 요구될 것이 확실하다. 이미 유럽과 북미의 기술선진국을 중심으로 이러한 기술이 축적되고 있으나, 안타깝게도 국내에서는 7xxx계열 알루미늄합금에 대한 마찰교반용접 공정기술 확보를 위한 연구와 개발이 눈에 띄지 않는다. 이에 본 연구에서는 가장 대표적인 7xxx계열 알루미늄합금 중 하나인 7075-T6 판재에 대하여 마찰교반용접을 실시하여 시험편을 제작하였다. 주요 공정인자인 툴의 회전속도는 800~1,200RPM, 이송속도는 500~250mm/min., 틸팅각은 2도의 조건에서 시험편을 제작하였다. 인장시험, 충격시험 및 경도시험을 통하여 용접부의 기계적 특성을 평가하였으며, 광학현미경과 주사전자현미경을 이용하여 미세조직을 관찰하였다. 이 결과들을 토대로, 500MPa급 고강도 알루미늄합금 7075-T6 판재에 대한 마찰교반용접 공정범위를 제안하고, 각 공정조건, 기계적 특성 및 미세조직의 상관관계 및 전주기적 거동을 확인하였다.