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In this work, TiC nanoparticles (TiCps) reinforced 7075 aluminium alloy was fabricated via an oscillating laser-arc hybrid additive manufacturing process. To show the beneficial effect of TiCps addition on microstructure and mechanical properties, a conventional 7075 aluminium alloy was also manufactured for comparison. Upon the addition of TiCps, remarkable grain refinement was achieved with a decrease in average grain size from 111.8 to 12.5 µm, and grain boundary segregation was alleviated. It was also found that many secondary phases precipitated at the grain interior in the deposit with TiCps. Owing to the refined microstructure and favourable precipitation, as-deposited 7075 aluminium alloy with TiCps showed enhanced tensile properties of ultimate tensile strengths of 346 and 355 MPa along scanning and build directions. [ABSTRACT FROM AUTHOR]

• The influence of beam oscillating amplitudes on depositions was studied detailly. • O-LHAM with wide oscillating amplitudes was applied to fabricate Al-Mg-Sc alloy. • The thin wall with sound surface quality was achieved at the amplitude of 4 mm. • Full equiaxed grains were obtained when the amplitude beyond 2 mm. • The optimal mechanical performance was achieved at the amplitude of 4 mm. The oscillating laser-arc hybrid additive manufacturing was applied to fabricate Al-Mg-Sc alloy and the effect of beam oscillating amplitude on macro/micro-morphology and the mechanical properties were investigated in this study. With the oscillating amplitude increased from 0 to 6 mm, the stirring effect of laser beam on molten pool was firstly enhanced due to the expanded active region and then weakened because the laser spot located at the edge of pool. As a result, the improved forming quality, the reduced porosity and the refined microstructures were achieved when the amplitude reached 4 mm, and then negative effect occurred when the amplitude was 6 mm. Eventually, the optimal mechanical performance was achieved at the amplitude of 4 mm and the as-deposited tensile properties reached 353 MPa and 24 % for UTS, and EL in vertical direction, respectively, which were 13.5 % and 50 % higher than that of 0 mm. [ABSTRACT FROM AUTHOR]

The refined microstructure and enhanced mechanical properties of aluminum alloys containing Sc have attracted a great deal of attention in the recent past. In this work, a wire-based process of laser-arc hybrid additive manufacturing (LHAM) was developed and utilized to fabricate Al–Mg–Sc alloy thin wall deposits. The macro morphology, microstructural features and mechanical properties of LHAMed Al–Mg–Sc alloy were systematically investigated in comparison with wire and arc additive manufacturing (WAAM) under two processing conditions, i.e., same arc current (WAAM_SA) and same heat input (WAAM_SH). The surface quality of LHAMed deposits was significantly improved compared to that of WAAM_SA due to the stabilized effect of laser on arc behaviors. The deposits made by LHAM showed a refined and homogeneous microstructure compared to that of WAAM_SH under the condition of the same heat input, and a similar grain size with that of WAAM_SA even using a higher heat input. The microhardness results showed the LHAM had a higher and more stable microhardness distribution due to the homogeneous microstructure and less burning loss of magnesium. The as-deposited walls of LHAM and WAAM_SA showed a similar ultimate tensile strength (UTS) of more than 345 MPa for both horizontal and vertical directions, which is slightly higher than that of WAAM_SH. The as-deposited wall of LHAM also showed an exceptional elongation of about 26%, which is higher than that of both WAAM_SA and WAAM_SH samples, especially in the vertical direction, indicating less anisotropy in mechanical properties. • The Al–Mg–Sc alloy thin wall with high surface quality was obtained by LHAM. • The grain size and second phases of LHAM were refined in comparison with WAAM_SH. • The thin wall made by LHAM showed the minimum fluctuation of microhardness. • The enhanced tensile properties in both directions were achieved by LHAM. [ABSTRACT FROM AUTHOR]

Wire-based additive manufacturing (AM) presents promising opportunities for making large components with high-price materials, such us aluminum alloys containing expensive rare earth element of scandium (Al-Sc alloy). However, wire-based AM of structurally sound and defect-free aluminum components is still challenging. In this work, an oscillating laser-arc hybrid additive manufacturing (O-LHAM) process was developed to fabricate thin-wall parts of Al-6Mg-0.3Sc alloy. To show the effect of oscillating laser beam on macro/micro-structure, porosity and mechanical properties, wire and arc additive manufacturing (WAAM) of Al-6Mg-0.3Sc alloy part was also performed for comparison. The results showed that the surface roughness of O-LHAM samples was reduced by 34.7% and the effective wall width was increased by 20% when maximum width of the wall was same with WAAM. The porosity was significantly mitigated and the microstructures was refined and homogenized due to the string effect of beam oscillating in the molten pool. The as-deposited wall of Al-Sc alloy showed an ultimate tensile strength of more than 350 MPa, reaching an exceptional level among the as-deposited aluminum alloy. The O-LHAM samples showed a higher elongation and lower anisotropy, which are resulted from the mitigated porosity and homogenized microstructure. [Display omitted] ● Al-6Mg-0.3Sc alloy thin-wall part was fabricated by O-LHAM. ● The surface quality of O-LHAM sample was improved in comparison with that of WAAM. ● The porosity was mitigated due to the stirring effect of oscillating laser beam. ● The microstructure was refined and homogenized in O-LHAM sample. ● The as-deposited Al-6Mg-0.3Sc alloy showed an UTS of more than 350 MPa. [ABSTRACT FROM AUTHOR]