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EXTRUDING AND DRAWING TANTALUM ALLOYS TO COMPLEX THIN H-SECTION.
Final technical rept. 1 Jul 63-31 Jan 66,
TEXTRON INC WEST CONCORD MA NUCLEAR METALS DIV
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Techniques were established for fabricating thin H-sections of two tantalum alloys, Ta-10W and Ta-30Cb-7.5V, by a combination of extrusion and drawing operations. Difficulty was experienced with the Ta-30Cb-7.5V during extrusion because of hot shortness. Evacuated, thin-walled molybdenum-clad billets of wrought tantalum alloy were extruded at 3500 F from a 3-38-inch diameter liner with glass lubrication into 116-inch thick H-sections. Cladding was necessary to prevent contamination of the billet surface from reaction with the glass lubricant and atmosphere during extrusion. Solid ceramic dies of zirconia were used to overcome the problems of wear and softening with zirconia-coated steel dies due to the high temperature and long lengths of the extrusions. The extruded sections were chemically stripped of the molybdenum cladding, etched to remove contaminated surface metal where excessive clad thinning had occurred during extrusion, and then vacuum annealed at 2750 F prior to drawing. The annealed sections were cold-drawn at 3-8 reductions per pass to 0.040-inch thickness. Testing of the extruded and final drawn H-sections included chemical analysis, metallographic examination, and tensil tests at room temperature. Tensile tests and stress rupture tests were made at 2500 F in vacuum with annealed specimens from selected final drawn H-sections. The tantalum alloys proved more difficult to fabricate than other refractory metals. Although techniques were developed, considerably more work is needed to establish the best process for large-scale production of complex thin shapes. In particular, die designs for extrusion and drawing would have to be established for each new shape. Author
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