Further abbreviation of the machining schedule for producing surface-damage-free beryllium

The feasibility of reducing the number of finishing lathe cuts in the machining of beryllium that must be free of surface damage after subsequent heat treating or etching was evaluated. Tensile, impact, and bend tests were used to determine the effects of surface damage on the mechanical properties. Optical and electron microscopic examinations were used to determine the metallographic effects of surface damage. Four different machining schedules were evaluated. The results indicate that a carefully controlled one-finishing pass method is equivalent to the carefully controlled two-finishing pass method presently being used to produce damage-free beryllium at Rocky Flats. Scanning electron microscopy indicated new information concerning the damage on machined beryllium surfaces. Sharply and deeply cracked or torn regions of metal about 1/2 mil or 10 microns in width appear periodically along the machining striations.