Diffusion Welding of Wrought Beryllium.

Abstract : The objective of the study was to produce diffusion welds in wrought berrylium sheet having mechanical properties, primarily tensile strength approaching those of the base metal at temperatures up to 800 F. Beryllium sheet, 1/16 to 1/4 inch thick and containing 1 to 2 percent BeO, was butt welded in vacuum at about 10 to the -6th torr. Welds made in the low-oxide, 1/8-inch-thick sheet at 1550 F for 1-3/4 hours with 5-10 percent deformation after etching in a HNO3-HF-H2O solution had a yield-strength efficiency of 93 percent at room temperature and 98 percent at 800 F. Tensile elongation in 1 inch was less than 1 percent at room temperature and 10 percent, or a third of the base-metal elongation, at 800 F. Using the same welding parameters, lower weld strengths were obtained with 1/4-inch-thick sheet containing 0.9 percent BeO. Vapor-deposited or preplaced foil intermediates were not found to significantly aid welding. It was concluded that the tensile properties of diffusion welds could be improved by reducing the amount of impurities, particularly BeO, on the joint surfaces, by shortening the welding time, and by preparing smoother surfaces for welding. (Author)