Effect of adding cold wire of aluminum alloy ۴۰۴۳ on the microstructure and mechanical properties of thin-walled austenitic stainless steel ۳۱۶L produced via wire arc additive manufacturing

Wire Arc Additive Manufacturing (WAAM) with cold wire (CW-WAAM) offers several advantages over conventional WAAM processes. In addition to enhancing deposition rate and productivity, CW-WAAM can possible the input energy independent of the wire feed rate, thereby enabling more precise control of process parameters. This approach also reduces penetration depth, minimizes the heat-affected zone, and achieves dilution levels below ۲۰%, which are beneficial for alloying and microstructural refinement. In the present study, a thin alloy wall was fabricated by introducing aluminum alloy ER۴۰۴۳ as cold wire into austenitic stainless steel ER۳۱۶L using CW-WAAM with a reciprocating torch pattern. The wall was deposited at a nominal current of ۱۲۰ A, with the cold wire torch positioned at a ۴۵° angle, and built up in ۲۲ successive layers. Optical microscopy revealed distinct microstructural variations across the wall. In the central region, low cooling rates and heat accumulation from layer-by-layer deposition promoted the growth of columnar and coarse grains aligned with the heat transfer direction. In contrast, the upper and lower regions exhibited finer grain structures. Aluminum-rich precipitates were observed within grains and along grain boundaries, though their distribution was non-uniform, indicating the necessity of post-deposition heat treatment. Mechanical characterization confirmed these microstructural findings. Tensile specimens demonstrated increased strength but fractured in a brittle manner, with the highest tensile strength recorded for the flat sample (۵۵۴ MPa). Microhardness testing further showed that hardness enhancement in the initial and final layers correlated with finer microstructures. The average hardness of the wall was measured at ۳۲۱ HV, underscoring the influence of microstructural heterogeneity on mechanical performance.

کلیدواژه ها:

Wire arc additive manufacturing ، Cold wire ، Austenitic stainless steel ۳۱۶L ، Aluminum alloy ۴۰۴۳ ، Microstructure ، Mechanical properties