A METHOD OF FRACTURE TOUGHNESS MEASUREMENT AND EFFECT OF PARTIAL ANNEALING ON MONOLITHIC THICK COLD SPRAYED ALUMINUM 6061 DEPOSITS

摘要

Cold spray is a solid-state material deposition method that can create thick (>10mm) metal layers that adhere metallurgically to a base part or a substrate. Numerous potential applications exist, such as returning worn mechanical parts to their original dimension, extending their service life. For fatigue applications the fracture properties of cold spray deposited material must be known but little to no literature has been found on the fracture behavior of cold spray deposited material alone, which prompted the study presented here. Fracture toughness specimens were manufactured by depositing thick cold-sprayed layers of powdered aluminum 6061 onto an aluminum 6061 substrate using N_2 as the carrier gas. The substrate was then machined away, and monolithic miniature compact tension fracture toughness specimens were machined from the cold spray deposit itself, following ASTM E-1820. The fracture behavior of the cold sprayed material was then experimentally determined using the elastic-plastic J-resistance method for compact test specimens described in ASTM E-1820. Two specimen conditions were successfully tested, "as-sprayed" and "partially annealed". The results are that the Mode-I elastic-plastic stress intensity factor J_I has been successfully measured for cold-spray deposited material alone, and that partially annealing a cold-spray deposit can dramatically increase its fracture toughness.