SOLIDIFICATION AND SEGREGATION IN WELDING OF BINARY ALLOYS.
ARMY MATERIALS RESEARCH AGENCY WATERTOWN MASS
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The report concerns the initial effort of a long-range program designed to determine the effects that welding variables and base metal chemistry have upon the solidification mode of weld metals. To minimize the complexity of the problem, two relatively pure binary alloys having high solid solubility were selected as parent materials. Weld metals were produced in these parent materials, using a stationary inert-gas shielded tungsten arc and a constant current welding mode. Energy inputs were regulated by controlling arc operation time. Efforts were made to limit heat flow so that experimental procedures would develop constant and reproducible results. Thus far in the program, studies have been limited to metallographic and electron beam microanalysis of the base and weld metal microconstituents. The effects of energy input have been studied and some effects that base metal chemistry has on the growth mode of a solid interface have been observed. Information on the segregation effect in the base metal structures and substructures of the columnar weld metal grains are reported. Photomicrographs showing the growth mode and chemical segregation effect in high and low energy input weld metals are presented. Data developed from the electron beam microprobe analysis are tabulated and correlated with the physical appearance of weld metal growth products. The metallographic study shows that the growth mode of the solid interface at the fusion line is essentially 100 percent epitaxial in nature. Electron beam microprobe analysis shows that chemical micro-segregation in the weld metal growth structures is small, and similar to that in the parent metal. Author
- Properties of Metals and Alloys
- Fabrication Metallurgy