Search Results (3)

The rapidly growing field of metal additive manufacturing (AM) has enabled the fabrication of near-net-shape components with complex 3D structures in a more reliable, productive, and sustainable way compared to any other manufacturing process. The productivity of AM could be significantly increased combining conventional and AM technologies. However, the application at an industrial level requires the validation of the AM process itself and the assurance of the soundness of the junction between the substrate and the deposited metal at a sufficiently rapid metal deposition rate. In this work, the validation of additively manufactured samples of Al-5356 alloy was performed. These were manufactured partially via an ablation casting process and partially via laser metal deposition using a metallic wire (LMwD). The deposited material showed low porosity levels, i.e., below 0.04%, and a small number of lack-of-union defects, which are detrimental to the mechanical properties. In the tensile samples centred at the junction between the ablated and deposited materials, it was found that when the AM part of the sample exhibited no lack-of-union defects, the region manufactured using LMwD showed higher strength than the ablation-cast part. These results suggest that the combination of ablation casting and LMwD is a competitive technique for the manufacturing of Al-5356 alloy parts with complex geometries. Full article

This study examines the microstructure and mechanical properties of 5356 aluminum alloy under low heat input conditions during arc additive manufacturing, focusing on the challenges posed by excessive heat input, which hinders specimen formation and affects dimensional accuracy. The study analyzes the characteristics of single-pass multilayer straight-walled specimens fabricated under varying low heat input conditions, along with evaluations of their mechanical properties, including their microstructure, microhardness, and tensile strength. This study demonstrates that as the heat input increases from 87.5 J/mm to 190.0 J/mm, the width of the vertical wall specimens increases significantly, whereas the change in single-layer height remains minimal. The specimen width increases from 5.22 mm to 8.87 mm, representing a change of 3.65 mm, while the single-layer height increases by only 0.16 mm. The microstructure primarily consists of the α(Al) matrix and the skeletal β(Al₃Mg₂) phase. As heat input increases, some of the β(Al₃Mg₂) phase dissolves, resulting in a decrease in its distribution density, a reduction in its quantity, and an increase in its size. The average hardness increases from 69.40 HV at 87.5 J/mm to 77.89 HV at 154.2 J/mm, before decreasing to 73.56 HV at 190.0 J/mm. As the heat input increases, the tensile strength and elongation of both horizontal and vertical specimens initially increase and then decrease. The tensile strength and elongation of the horizontal specimens are slightly greater than those of the vertical specimens. The microstructure and mechanical properties vary across different regions. In the upper region, the β(Al₃Mg₂) phase is uniformly distributed, with high density and small size. The fracture surface exhibits fine, uniform dimples, displaying the best microhardness and mechanical properties, with a tensile strength of 245.88 MPa. In the middle region, the distribution density of the β phase decreases, the size increases, and the dimples become slightly coarser. Consequently, the microhardness and mechanical properties decline. At the bottom, due to the higher cooling rates, the β phase does not dissolve significantly. The distribution density is high, the dimples are large and uneven, and the microhardness and mechanical properties are the lowest, with a tensile strength of 236.00 MPa. Full article

The CMT-Twin-based wire and arc additive manufacturing (WAAM) process for 5356 aluminium alloy has been investigated focusing on the optimisation of welding parameters to maximise the deposition rate while avoiding segregation-related problems during solidification. For that, different conditions have been studied regarding interpass dwell time and the use of forced cooling. The larger heat input produced by the double-wire CMT-Twin process, compared to the single-wire CMT, creates vast segregations for less intensive cooling conditions and short dwell times that can induce cracks and reduce ductility. Thermography has been applied to set a maximum local temperature between consecutive layers avoiding those segregations and pores, and to optimise the total manufacturing time by varying the interpass dwell time along the height of the wall. Only a constant interpass long dwell time of 240 s and the new optimised strategy were effective in avoiding merged segregations, reducing the latest total manufacturing time by 36%. Obtained tensile properties are comparable to other works using WAAM for this alloy, showing lower properties in the vertical orientation. The use of CMT-Twin-based welding technology together with variable interpass dwell time controlled by thermography is an interesting alternative to build up parts with wall thicknesses around of 10 mm in a reduced time. Full article