Enhanced high-temperature mechanical properties of laser-arc hybrid additive manufacturing of Al-Zn-Mg-Cu alloy via microstructure control

Abstract

Recently, rapid and cost-effective additive manufacturing solutions for lightweight aluminum alloys with excellent high-temperature mechanical properties have been increasingly in demand. In this study, we combined laser-arc hybrid additive manufacturing with solution and artificial aging treatments to achieve Al-Zn-Mg-Cu alloy with favorable high-temperature strength via microstructure control. Hydrogen pores became the major defect in the as-deposited and heat-treated specimens. The continuous distribution of eutectics with hard-brittle characteristics at the grain boundaries was destructed following heat treatment. High-density η′ precipitates were uniformly dispersed in the heat-treated Al-Zn-Mg-Cu alloy, whereas appeared coarsened and dissolved at 473 K, owing to the rapid diffusion of Zn and Mg. The average 0.2% yield strength (318 ± 16 MPa) and ultimate tensile strength (362 ± 20 MPa) at 473 K after heat treatment were enhanced by approximately 58% and 51%, respectively, compared to those of the as-deposited specimen. In addition, the η′ precipitates contributed to lattice distortions and strain fields, which prevented dislocation motion and increased slip deformation resistance at high temperatures. The as-deposited specimen exhibited intergranular fracture at 473 K, with cracks preferring to propagate along the aggregated eutectics. However, crack propagation proceeded in the sections with more pores in the heat-treated specimen. Our approach may provide a valid option for achieving aluminum alloys with excellent high-temperature mechanical properties.