Analysis of heat input, microstructure evolution, crystallographic texture, and mechanical performance through layer-by-layer characterization of WAAM-fabricated Al–5Mg alloy

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2026年3月17日

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Raghavendra Pai,
Vijeesh Vijayan,
Augustine Samuel,
K. Narayan Prabhu

摘要

The present study involves analysis of the heat input, microstructure evolution, crystallographic texture and mechanical performance of Al–5Mg alloy deposited in a three-layer configuration. Samples were fabricated using single (SL), double (DL) and triple (TL) layer deposition at variable voltages (13–19.5 V), a gas flow rate of 10 l/min (99.99% Ar) and a wire feed rate of 4.1 m/min. Heat input was estimated using inverse heat conduction analysis. The estimated peak heat flux values for the third cycle of 14.5 V, 15 V and 19 V were 649 kW/m², 505 kW/m² and 1306 kW/m² respectively. Heat flux transients were correlated with grain morphology. The average grain sizes and orientations at 14 V for SL, DL and TL deposition were 54.04 ± 2.36 µm 47.69 ± 2.60 µm and 59.28 ± 3.456 µm respectively with a [111] plane orientation. The average surface roughness of the 14.5 V sample was 3.89 µm and 14.64 µm for the second and third layers of deposition respectively. Fine equiaxed grains of average size 52 ± 3.2 µm with partially fused boundaries were observed for voltages in the range 15–16 V with the formation of β phase alongside the α-Al phase. The formation of β phase occurred near grain boundaries resulting in an increase in porosity by 10.35%. The grain size increased to 98 ± 8 µm for + 19 V deposition with an elongated columnar grain structure. For 19 V the average surface roughness was 47 µm across the three layers of deposition with higher porosity. Transmission electron microscopy revealed the formation of nanocrystalline precipitates and Mg₂Al₃ phase at a higher thermal gradient between the interlayers. Fractography revealed the formation of voids above 15 V while TEM analysis confirmed the presence of Mg₂Al₃ along the grain boundaries beyond 15 V suggesting that the formation of this intermetallic phase promoted void initiation at elevated voltages.