PNNL

Abstract

Electroplating was used as a purification method and produced thick (3.2 mm-12.2 mm) copper deposits of ultra-high radiopurity. Due to the extreme thickness of these electrodeposits compared to traditional electroplating, characterization is necessary to prevent costly failures and ensure device reliability. The deposition rate was carefully controlled to maintain a uniform growth front and required plating for a continuous eight months in order to produce the 12.2 mm thick copper specimen. Tensile testing shows the electroplated copper to exhibit significant strain hardening as would be expected with Face Centered Cubic (FCC) materials, indicating the material is free of significant defects and voids. Testing of eight tensile samples machined according to ASTM-E8 specifications exhibited yield strengths of 95±4 MPa. Hardness was measured to be 79.8 ± 5.3 HV using a 200gf load. Microstructure and deformation showed the grains to be highly aligned with respect to the growth direction, Electron Backscatter Diffraction (EBSD) showed the development of a texture.