Effect Of Machining On Properties Of Impact Ground Beryllium

Previous studies indicated that twinning and microcracks introduced during machining degrade the mechanical properties of ingot beryllium and earlier grades of powder-origin beryllium. In this study on impact-ground beryllium we found that twinning caused by machining lowered the ultimate strength from 360 to 290 MPa (52,000 psi to 42,000 psi) and the elongation from 4% to less than 1% in the longitudinal direction--with similar results for the transverse direction. It is possible to restore the mechanical properties by chemically removing the damaged layer or by heat treatment. It is also possible to avoid machining damage; mechanical properties of a properly machined beryllium can be as high as carefully etched beryllium.