Microstructure and temperature development in copper welded by the FSW-process
2003 (English)In: 4th International Symposium on FSW, Park City, USA, April, 2003, 2003Conference paper (Refereed)
The use of Copper canisters with cast iron inserts is one of the proposed methods for long time deposition of nuclear fuel waste. The joining of the lid and possibly the base of the canister can be performed with Friction Stir Welding (FSW). A thorough understanding of the microstructure development in these welds is of major importance, since defects must be avoided. The microstructure and hardness profiles were investigated for two FSW conditions, at the beginning of the weld when there are essentially cold conditions, and when the steady state is reached. In cold welds the features of the nugget are very similar to that observed when FSW-joining aluminium. However, when the welding conditions reach the steady state, the nugget gets wider and the hardness is lower than in the cold weld.
Electron Back Scatter Diffraction (EBSD) visualisation has been used to determine the grain size distribution of, twins and misorientation within grains. The orientation maps show a fine uniform equiaxed grain structure. There is no major misorientation within the grains in the nugget or at the root, but 25 mm from the weld centre the misorientation is large. This confirms that this area lies within the Thermal Mechanical Affected Zone (TMAZ) and is partially recrystallised. The root has many more annealing twins than the nugget. This indicates that the nugget has experienced deformation after recrystallisation. A model has been used to correlate heat flow to the grain size and the hardness distributions.
Place, publisher, year, edition, pages
friction stir welding, microstructure, defect, void, copper, process parameter
Materials Engineering Metallurgy and Metallic Materials
IdentifiersURN: urn:nbn:se:kth:diva-12010OAI: oai:DiVA.org:kth-12010DiVA: diva2:294076
QC 201007162010-02-162010-02-162010-12-07Bibliographically approved