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마찰교반용접된 Al 6061-T651 합금의 응력부식균열 거동
임성곤,김상식,이창길,김성준 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.3
In the present study, corrosion behavior of friction stir welded (FSWed) Al 6061-T651 with varying welding parameters, including rotating and welding speeds, were examined. The 4 nun thick Al 6061-T651 alloy plates were friction stir welded. The resistance to corrosion was slightly improved, or at least did not decrease, for FSWed AI 6061-T651 alloy in 3.5% NaCl solution compared to the parent material. The effect of different welding conditions on the corrosion resistance was minimal. The micrographic and fractographic observations strongly suggested that the change in corrosion behavior of FSWed Al 6061-T651 was largely related to the clustering of coarse Mg₂Si precipitates, due to the whirling and casting action by severe plastic flow in the weld zone. Low welding speed and/or high rotating speed tended to encourage the plastic flow per unit time and consequently the clustering of coarse precipitates. The resistance to SCC in 3.5% NaCl solution was considerably higher for the FSWed AI 6061-T651 compared to that of the PM counterpart. The improved SCC resistance for the FSWed specimen was due to the fact that the stress corrosion cracks were enhanced at the boundary between the DXZ and the HAZ due to the greatest galvanic corrosion potential difference between the two phases, while the tensile fracture occurred at the other area where the strength level was the lowest. (Received October 29, 2004)
마찰교반용접된 각종 알루미늄 합금의 미세조직과 인장 특성
임성곤,김상식,이창길,김성준 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.11
Tensile behavior of friction stir welded Al 6061-T651, Al 7075-T6 and Al 5083-H32 alloy plates joined with different tool rotating and welding speeds was examined in the present study. Typical microstructure of friction stir welded Al alloy consists of three zones, including dynamically recrystallized zone (DXZ), thermomechanically affected zone (TMAZ) and heat affected zone. The tensile strength decreased by approximately 15 to 20% for age-hardened Al 6061 and Al 7075 accompanied with a slight increase in tensile elongation. Al 5083-H32 showed an approximately 20% increase in tensile elongation with no notable change in tensile strength. The tensile behavior of friction stir welded Al appeared to be strongly related to not only the frictional heat and microstructural evolution but also the amount of plastic flow and clustering of coarse precipitates.
마찰교반 용접된 Al 6061-T651 합금의 인장 특성
임성곤,김상식,이창길,김성준 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.1
Tensile behavior of friction stir welded Al6061-T651 alloy plate joined with different tool rotating and welding speeds was examined in the present study. Within the range of processing parameters where the welding defects were not observed, the tensile elongation of friction stir welded Al6061-T651 alloy plate was greatly improved with increasing welding speed and/or decreasing rotating speed. The change in the strength level was, however, marginal. For those specimens with low tensile elongation values, clusters of coarse Mg2Si precipitates were often observed in the vicinity of fractured area. Severe plastic flow occurred during friction stir welding, particularly for the specimens joined with low welding speed, appeared to be responsible for the clustering and eventually lower the tensile elongation.
임성곤(S. G. Lim),강신우(S. W. Kang),박건형(G. H. Park),김성환(S. H. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
The forging of magnesium is restricted to a few industries that aerospace parts. As increasing interests in the environment and enforcing strong regulations on exhaust gases and carbon dioxide in developed countries, efforts into developments in magnesium forging techniques have been making more briskly with transportation machine maker as the center. In particular, growing demands for a fuel-efficient vehicle, various efforts into lightweight of parts are putting forth. In this work, high strength commercial AZ80 and ZK60 Magnesium Alloys were forged in order to observe the changes in characteristics to the process. Changing variable forging temperature and forging speed of magnesium feedstock, magnesium control arms for chassis component were manufactured. Carrying out different heat treatments (T4 and T6), the changes in characteristics were investigated.