Formation and microstructure of banding in a copper friction stir weld was studied using scanning electron microscopy, electron backscatter diffraction, and nanoindentation. Unlike in aluminium, banding only appears in ‘cold’ friction stir welding (FSW) welds of copper. Banding is formed by layers of small and large grains. It was noticed that higher local misorientations and small grain size correlate in the welds. Owing to differences in the restoration processes of copper and aluminium, texture changes are not visible in copper even though they are in aluminium. Texture of copper FSW welds is weak and independent of the grain structure of the base material, because in the steady state dynamic recrystallisation, the restoration process of copper, the grain structure is mainly dependent of the processing parameters. The hardness differences between the small and large grains are small.
FondaRW, BingertJF: ‘Texture variations in an aluminium friction stir weld’, Scr. Mater., 2007, 57, 1052–1055.
12.
AhmedMMZ, WynneBP, RainforthWM, ThreadgillPL: ‘Quantifying crystallographic texture in the probe dominated region of thick section friction stir welded aluminium’, Scr. Mater., 2008, 59, 507–510.
13.
PrangnellPB, HeasonCP: ‘Grain structure formation during friction stir welding observed by the stop action technique’, Acta Mater., 2005, 53, 3179–3192.
14.
SchneiderJ, BeshearsR, NunesAC: ‘Interfacial sticking and slipping in the friction stir welding process’, Mater. Sci. Eng.A, 2006, A435, 297–304.
15.
SavolainenK, MononenJ, SaukkonenT, HänninenH, KoivulaJ: ‘Friction stir weldability of copper alloys’, Proc. 5th Int. Friction Stir Welding Conf., Metz, France, September 2004, The Welding Institute.
16.
XieGM, MaXY, GengL: ‘Development of a fine grained microstructure and the properties of a nugget zone in friction stir welded pure copper’, Scr. Mater., 2007, 57, 73–76.
17.
SaukkonenT, SavolainenK, MononenJ, HänninenH: ‘Microstructure and texture analysis of friction stir welds of copper’, in: ‘Materials processing and texture: ceramic transactions’, (ed. RolletA D, ed), Vol. 200, 53–60; 2008, Pittsburgh, PA, John Wiley & Sons.
18.
HasegawaM, YamamotoM, FukutomiH: ‘Formation mechanism of texture during dynamic recrystallization in γ-TiAl, nickel and copper examined by microstructure observation and grain boundary analysis based on local misorientations measurements’, Acta Mater., 2003, 51, 3939–3950.
19.
McDonaldDT, HumphreysFJ, BatePS: ‘Nucleation and texture development during dynamic recrystallization of copper’, Mater. Sci. Forum, 2005, 495–497, 1195–1200.
20.
HumphreysFJ, HatherlyM: ‘Recrystallization and related annealing processes’, 2nd edn, 497; 1995, Oxford, Elsevier Science.
21.
MiuraH, SakaiT, HamajiH, JonasJJ: ‘Preferential nucleation of dynamic recrystallization at triple junctions’, Scr. Mater., 2004, 50, 65–69.
22.
SorensenCD, NelsonTW, NelsonBD, AbbasiM: ‘Tool features and extended plasticity mechanisms in FSW of 304L’, Proc. 21st Int. Offshore and Polar Engineering Conf., Maui, Hawaii, USA, June 2011, The International Society of Offshore and Polar Engineers.
