The objectives of this work were to characterise and understand the effects of circular magnetic arc deflection (arc stirring) on grain structure refinement of gas tungsten arc weld beads made in Inconel 690 substrates. Welds were made at various arc stirring frequencies (1·5–50 Hz), and microstructures were analysed using optical and electron backscattered diffraction microscopy. Optimum refinement of grain size occurred at a stirring frequency of ∼7 Hz. Analysis of computational fluid flow, heat transfer and solidification model results suggested that grain detachment was the primary mechanism for grain refinement.
DavidS. A. and VitekJ. M.: ‘Correlation between solidification parameters and weld microstructures’, Int. Mater. Rev., 1989, 34, 213.
2.
KouS.: ‘Welding metallurgy’; 1987, New York, John Wiley and Sons Inc.
3.
SimpsonR. P.: ‘Controlled weld-pool solidification structure and resultant properties with yttrium inoculation of Ti–6Al–6V–2Sn welds’, Weld. J., 1977, 56, 67s–77s.
4.
SivaprasadK. and Ganesh SundaraS. Raman: ‘Current pulsing on fatigue behavior of alloy 718 TIG weldments’, Mater. Sci. Eng. A, 2007, A448, 120–127.
5.
SundaresanS., Janaki RamG. D. and Madhusudhan ReddyG.: ‘Microstructural refinement of weld fusion zones in a-b titanium alloys using pulsed current welding’, Mater. Sci. Eng. A, 1999, A262, 88–100.
6.
TewariS. P.: ‘Influence of vibration on grain size and degree of grain refinement in mild steel weldment’, J. Mater. Res., 1993, 8, 2228–2230.
7.
ArakawaT., HiranoK., IshidaA., KokawaH. and SatoY. S.: ‘Effects of magnetic stirring and grain structure on ultrasonic characteristics in Inconel overlay-welds’, Proc. 5th Int. Conf. on ‘Trends in welding research’, (ed. J. M. Vitek et al.), 67; 1998, Stone Mountain, GA, ASM International.
8.
MousaviM. G., HermansM. J. M., RichardsonI. M. and den OudenG.: ‘Grain refinement due to grain detachment in electro- magnetically stirred AA7020 welds’, Sci. Technol. Weld. Join., 2003, 8, 309–312.
9.
PearceB. P. and KerrH. W.: ‘Grain refinement in magnetically stirred GTA welds of aluminum alloys’, Metall. Trans. B, 1981, 12B, 479–486.
10.
VollertsenF. and ThomyC. J.: ‘Magnetic stirring during laser welding of aluminum’, J. Laser Appl., 2006, 18, 28–34.
11.
Koteswara RaoS. R., Madhusudhana ReddyG., KamarajM., Prasad RaoK.: Mater. Sci. Eng. A, 2005, A404, 227.
12.
LimY. C., YuX., ChoJ. H., SosaJ., FarsonD. F., BabuS. S. and McCrackenS., ‘Effect of magnetic stirring on grain structure refinement. Part 1: autogenous nickel alloy welds’, Sci. Technol. Weld. Join., 2010, in press.
13.
ChoM. H., LimY. C. and FarsonD. F.: ‘Simulation of weld pool dynamics in the stationary pulsed gas metal arc welding process and final weld shape’, Weld. J., 2006, 85, 271s–283s.
14.
KumarA. and DebRoyT.: ‘Calculation of three-dimensional electromagnetic force field during arc welding’, J. Appl. Phys., 2003, 94, 1267–1277.
15.
LinM. L. and EagarT. W.: ‘Influence of arc pressure on weld pool geometry’, Weld. J., 1985, 64, 163s–169s.
16.
DuPontJ. N. and MarderA. R.: ‘Thermal efficiency of arc welding processes’, Weld. J., 1995, 74, 406s–416s.
17.
KouS. and LeY.: ‘Alternating grain orientation and weld solidification cracking’, Metall. Mater. Trans. A, 1985, 16A, 1887–1896.
18.
KouS. and LeY.: ‘Nucleation mechanism and grain refining of weld metal’, Weld. J., 1986, 65, 305s–313s.
19.
SundaresanS. and Janaki RamG. D.: ‘Use of magnetic arc oscillation for grain refinement of gas tungsten arc welds in α-β titanium alloys’, Sci. Technol. Weld. Join., 1999, 4, 151–160.
20.
LiT., LinX. and HuangW.: ‘Morphological evolution during solidification under stirring’, Acta Mater., 2006, 54, 4815–4824.
21.
HallA. C. and RobinoC. V.: ‘Association of microstructural features and rippling phenomenon in 304 stainless steel gas tungsten arc’, Sci. Technol. Weld. Join., 2004, 9, 103–108.
22.
CampanellaT., CharbonC. and RappazM.: ‘Grain refinement induced by electromagnetic stirring: a dendrite fragmentation criterion’, Metall. Mater. Trans. A, 2004, 35A, 3201–3210.
KumarA. and DuttaP.: ‘A Rayleigh number based dendrite fragmentation criterion for detachment of solid crystals during solidification’, J. Phys. D, 2008, 41D, 155501.
25.
SureshM. V., KrishnaB. V., VenugopalP. and RaoK. P.: ‘Effect of pulse frequency in gas tungsten arc welding of powder metallurgical preforms’, Sci. Technol. Weld. Join., 2004, 9, 362.
26.
AnaneivS., NikrityukP. and EckertK.: ‘Dendrite fragmentation by catastrophic elastic remelting’, Acta Mater., 2009, 57, 657–665.
27.
GaumannM., TrivediR. and KurzW.: ‘Nucleation ahead of the advancing interface in directional solidification’, Mater. Sci. Eng. A, 1997, A226, 763–769.
28.
GaumannM., BezenconC., CanalisP. and KurzW.: ‘Single-crystal laser deposition of superalloys: processing-microstructure maps’, Acta Mater., 2001, 49, 1051–1062.
29.
VitekJ. M.: ‘The effect of welding conditions on stray grain formation in single crystal welds - theoretical analysis’, Acta Mater., 2005, 53, 53–67.
