Abstract
Autogenous gas tungsten arc welding was performed on a continuous cast sheet (about 1 mm thick) of an Ni 3Al alloy (Ni 77.83Al 21.73Zr 0.34B 0.10) known as IC-50. The material was highly susceptible to cracking in the heat-affected zone (HAZ). The cracks in the HAZ were liquation cracks and occurred along the grain boundaries. There were occasional solidification cracks in the fusion zone (FZ) and they occurred along the main dendrite boundaries. Microporosities were observed in both the FZ and HAZ. Microprobe analysis showed Zr enrichment in HAZ regions where melting had taken place. Annealing the alloy at 1100 °C for 5 h produced Zr-rich particles. Welding after the annealing showed similar behavior to that without annealing, except that the partially molten region in the HAZ was reduced in size. The role of Zr segregation at the grain boundaries in causing partial melting is discussed.
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