Wire-based laser directed energy deposition of AA7075: effect of process parameters on microstructure and mechanical properties

Abstract

The process development for wire-based laser directed energy deposition of AA7075 is studied. Thin-wall structures are produced to investigate the process-microstructure-mechanical performance relationship. By optimizing the process parameters and building strategies, the minimal porosity level of 0.8% and 0.3% can be achieved in the continuous and discontinuous building strategies, respectively. The porosity level exhibits a primary dependence on the specific energy and a secondary dependence on the ratio between wire feed rate and laser scan speed. Thin-wall structures show an average hardness of 115 HV0.1. In two optimized building strategies, the ultimate tensile strength of 400 MPa is achieved without the cost of ductility (fracture strain of 9.2%). Large columnar grains with preferential orientation and the distribution of secondary phases relative to the loading direction during tensile tests contribute to superior mechanical properties.