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600 MPa급 플럭스 코어드 아크 용접금속의 저온균열에 미치는 예열 온도 및 미세조직의 영향
이명진 ( Myungjin Lee ),조경목 ( Kyungmox Cho ),강남현 ( Namhyun Kang ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.4
The influence of preheat and microstructure on cold cracking for high strength and low hydrogen flux cored arc (FCA) weld metal was analyzed using Y-groove test. The weld microstructure consisted of acicular ferrite and martensite. As the preheat temperature increased, the volume fraction of acicular ferrite increased and that of martensite decreased, thereby decreasing the volume expansion during the transformation from austenite to martensite. This result was consequently associated with a reduced cold cracking ratio. Cold cracking progressed mainly along the prior austenite grain boundary of martensite, and the fractograph of cold cracking consisted of intergranular fractures and quasi-cleavage fractures. With increasing the preheat temperature and decreasing the carbon equivalent, the fraction of intergranular fractures decreased and quasi-cleavage fractures increased. The microstructure related with intergranular fractures was martensite; quasi-cleavage fractures were associated with acicular ferrite.
용탕가압침투법에 의한 알루미늄 보레이트 강화 Mg-3Al-2Ag-1Zn 금속복합재료의 물성
강호준,배건희,박용하,한상호,박용호,조경목,박익민,Kang Hojune,Bae Gunhee,Park Yongha,Han Sangho,Park Yongho,Cho Kyungmox,Park Ikmin 한국재료학회 2005 한국재료학회지 Vol.15 No.12
In this study, aluminum borate whisker reinforced Mg-3Al-2Ag-1Zn matrix composites were fabricated by the squeeze infiltration technique. The purpose is to develop materials for elevated temperature applications. Microstructure observation revealed successful fabrication of the metal matrix composites, namely no cast defects such as porosity and matrix/reinforcement interface delamination etc. High temperature hardness and creep rupture properties were improved significantly with addition of Ag to the Al borate whisker reinforced Mg alloy composite. $Mg_3Ag$ phase formed during aging heat treatment could improve creep properties of the Mg matrix composites.