Selective laser melting of 7075 aluminum alloy inoculated by Al–Ti–B: Grain refinement and superior mechanical properties

Coarse column grain and hot cracking severely hinder the application of AA7075 aluminum alloy fabricated by selective laser melting (SLM). In this work, a novel grain refiner consisting of submicron TiH 2 and amorphous B particles was developed to control such features in SLM-fabricated AA7075 alloy. Crack-free and dense (TiH 2 +B)/AA7075 alloy was fabricated under optimal SLM processing. Results show that the addition of TiH 2 and B particles can convert coarse columnar grains into homogeneous equiaxed grains, decrease the average grain size from 29.1 μm to 2.3 μm, and consequently eliminate the hot-cracking in (TiH 2 +B)/AA7075 alloy. The remarkable grain refinement is mainly attributed to heterogeneous nucleation promoted by a combination of in-situ formed L1 2 -Al 3 Ti and TiB 2 nanoparticles. After T6 heat treatment, the (TiH 2 +B)/AA7075 alloy behaves superior mechanical properties(tensile strength of ∼582 MPa and ductility of ∼12.8%) to most previously reported SLM-fabricated 7075 alloys. Synergetic effects of crack elimination, grain refinement, and precipitation strengthening are responsible for the excellent mechanical properties. •A novel Al–Ti–B refiner was in-situ introduced into SLM of high-strength Al alloy. •Crack-free (TiH 2 +B)/AA7075 alloy with fine equiaxed grains was fabricated by SLM. •L1 2 -Al 3 Ti and TiB 2 nanoparticles synergistically promote grain refinement. •(TiH 2 +B)/AA7075 alloy behaves superior combination of strength and ductility.