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Kyle C. Lana, Daryush K. Aidun, Chao Liu, and Frederick M. Carlson:
Microstructure of gas tungsten arc welds under macrogravity conditions
Dec 15, 2008
Weld pool development during arc welding is determined by the arc-metal interaction, heat and fluid flow, thermo-physical properties of the base metals, and the associated boundary conditions. To control fluid flow as well as heat and mass transfer in an arc weld pool, the interaction of buoyancy, surface tension, electromagnetic, and the arc drag/pressure forces must be understood. Manipulation of these convective forces in the weld pool gives control of solidification morphology, compositional homogeneity, and allows for prevention of defects in the weld zone. Effects of enhanced buoyancy convection induced by simulating a high-gravity environment on 70Cu-30Ni, 316 austenitic stainless steel, and 2205 duplex stainless steel alloys have been investigated. Linear gas tungsten arc welds (GTAW) were performed at various glevels (1 g = 9.81 m/s2) using the multi-gravity research welding system (MGRWS). It was found that the aspect ratio of the weld fusion zone decreases as g-level increases. The heat-affected zone of the weld shows a narrower profile and exhibits smaller grain sizes in high-g environment.
Reduction of average dendrite spacing in the 316-fusion zone occurs with increasing g-level. The 2205 welds at high g contain more austenite phase in the fusion zone resulting in a lower volume fraction of ferrite in %.
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Microstructure of gas tungsten arc welds under macrogravity conditions
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