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RISS 인기검색어
- 검색키워드
- 저자 : Yucel Birol (검색결과 2 건)
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Effect of Cr and Zr on the Grain Structure of Extruded EN AW 6082 Alloy
Yucel Birol 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.4
The effects of Cr and Zr addition on the coarse grain surface layer in EN AW 6082 tube extrusions wereinvestigated. The decoration of the tube surfaces and the weld seams with coarse recrystallized grainsreflects the strain as well as the temperature gradients that predominate across the section of the tubesduring extrusion. The recrystallization resistance provided by Mn does not suffice to avoid the coarse surfacegrains. With structural features that are almost identical to those of the base 6082 alloy, the 6082alloy with 0.06 wt% Zr also fails to offer any improvement. The coarse grain surface layer is much thinnerand recrystallization is entirely avoided across the weld seams upon the addition of 0.15 wt% Cr. Thesuperior recrystallization resistance of the revised alloy is attributed to the increase in the population of theCr-rich Al(Cr,Mn,Fe)Si as well as (Al, Si)3Zr dispersoid particles. It is reasonable to conclude that the coadditionof Zr and Cr has a favourable impact on the resistance to recrystallization of EN AW 6082 alloy.
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Friction Stir Welding of Twin-Roll Cast EN AW 3003 Plates
Yucel Birol,Sefika Kasman 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.6
Twin-roll cast EN AW 3003 plates were butt-welded with friction stir welding and their structural features were identified. Sound welds were obtained in twin-roll cast EN AW 3003 plates at tool rotation speeds higher than 500 rpm. The ultimate tensile strength of the welded plates was 134 ± 3 MPa, comparable to the ultimate tensile strength of the original plate, at 146 MPa. The stirring action of the pin fractured the interdendritic network and coarse eutectic cells, replacing the dendritic features of the base plate with a uniform dispersion of very fine intermetallic particles across the stir zone. The thermal and mechanical cycles introduced during FSW relaxed the supersaturation of the cast plate, leading to the precipitation of intermetallic particles. This precipitation activity produced a particle population gradient that peaks inside the stir zone and dictates the etching response across the plate section. The material in direct contact with the rotating pin is severely deformed and is exposed to frictional heating and inevitably undergoes dynamic recrystallization. The very fine grain structure thus obtained suffers abnormal grain growth when annealed at high temperatures due to the effective pinning of the grain boundaries by the fine particles.
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