Mechanical properties and microstructures in zirconium deposited by injected powder laser additive manufacturing

The use of laser additive manufacturing based on melting of injected zirconium powder under localized shielding was evaluated in terms of microstructures and mechanical properties of thin wall structures. The material was characterized in both the laser travel and the build directions. The microstructures, tensile properties and fracture behavior were assessed for deposits made using as-received and recycled powder. Electron backscattered diffraction and transmission electron microcopy revealed a fine structure of Zr-α laths with nano-scale iron-rich precipitates at the lath interfaces. The properties of the fabricated components, which were made using new as-received powder were comparable to a Zr-2.5Nb alloy substrate, with yield strengths of over 569 MPa and uniform strains up to the ultimate tensile stress ranging from 8.5 to 9.9%. However, when recycled powder was used, the ductility dropped with total strains to failure of 1.0-7.5%, as a result of porosity and unmelted powder particles serving as brittle inclusions in the deposited material.