Abstract
Grain refinement is critical to surpassing the bottlenecks of inherent hot tearing of high-strength alu-minum alloys fabricated by additive manufacturing(AM).In this study,a synergistic grain-refining strategy including heterogeneous nucleation,solute-driven growth restriction and nanoparticle-induced growth restriction was introduced to control the microstructure of Al-Zn-Mg-Cu alloys during the laser powder bed fusion(LPBF)process.Crack-free Al-Zn-Mg-Cu alloys with significantly refined grains were safely fabricated via LPBF by coincorporation of TiC and TiH2 particles.In-situ L12-Al3Ti particles were produced to promote the heterogeneous nucleation.The grain growth was restricted by adding Ti so-lute,while introduced TiC nanoparticles(NPs)improved the density of heterogeneous nucleation sites and blocked grain growth physically.The resultant elimination of columnar grains and hot cracks in the(1 wt.％)TiC-and(0.8 wt.％)TiH2-modified Al-Zn-Mg-Cu alloy resulted in excellent ultimate tensile strength(UTS)of 593±24 MPa,yield strength(YS)of 485±41 MPa and elongation(EL)of 10.0％±2.5％under the T6 condition.This study provides new insights into improving the grain microstructure and mechanical properties of high-strength aluminum alloys during LPBF.
维普
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