Browsing by Author "Balla, S.K."

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    Effect of Process Parameters on Track Geometry and Porosity in Laser Direct Energy Deposition of High Strength Aluminum Alloy
    (Springer, 2024) Balla, S.K.; Manjaiah, M.; Selvaraj, N.; Bontha, S.
    Laser Directed Energy Deposition (LDED) is a metal Additive Manufacturing (Metal AM) process that has attracted significant attention due to its ability to produce complex geometries with material properties comparable to cast and wrought parts. High-strength aluminum alloys especially 2xxx, 6xxx, and 7xxx series are difficult to fabricate using LDED process since these alloys are prone to hot cracking due to rapid solidification during the LDED process. The focus of this work is to evaluate the effect of LDED process parameters on track geometry and porosity of Al7075 powder. The effects of process parameters such as laser power, scan speed, and powder flow rate on track geometry and porosity, were investigated using a Formalloy LDED machine via L27 orthogonal array of experiments. Increasing the laser power resulted in an increase in bead width and wetting angle, whereas increasing the scan speed led to a decrease in bead height and wetting angle and a minor increase in width. The results also showed a linear increase in wetting angle and bead height with increased powder flow rate, while the width of the bead remained relatively constant. Furthermore, it was also observed that increasing the laser power to 750 W resulted in a decrease in the cross-sectional porosity of the bead due to the availability of sufficient energy density thereby facilitating proper melting. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
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    The influence of laser direct energy deposition processing parameters on Al7075 alloy and Zr-modified Al7075 alloy
    (Springer Science and Business Media Deutschland GmbH, 2024) Balla, S.K.; Mallaiah, M.; Nagamuthu, S.; Gurugubelli, R.C.; Aranas, C.; Bontha, S.
    The Laser Directed Energy Deposition (LDED) technique in metal additive manufacturing (MAM) offers intricate geometries while maintaining material properties akin to cast and wrought components. However, challenges persist in fabricating high-strength aluminum alloys like 2xxx, 6xxx, and 7xxx series due to hot cracking during rapid solidification in LDED. This study addresses Al7075 hot cracking issue by introducing 1 wt% Zr. To evaluate this novel approach, the influence of process parameters on track geometry, porosity, microstructure, hardness, and tensile properties of both Al7075 and modified Al7075 (with 1 wt% Zr) was examined using an L27 orthogonal array of experiments. Findings indicate that increased laser power widens bead width and wetting angle. Conversely, higher scan speeds reduce bead height but marginally increase width, impacting wetting angle. Notably, the addition of Zr decreased porosity from 0.07 to 0.032%, indicating enhanced material quality. Microstructural analysis reveals Zr’s role in preventing solidification cracking by enhancing molten metal fluidity during solidification, transitioning the microstructure from columnar to equiaxed fine grain due to Al3Zr precipitates, and promoting grain refinement. This addition of Zr also improved hardness and tensile strength by 11% and 10%, respectively, attributed to Al3Zr precipitates’ role in grain refinement and precipitation strengthening within Al7075. In summary, incorporating 1 wt% Zr into Al7075 via LDED demonstrates promising improvements in microstructure, reducing porosity, enhancing mechanical properties, and mitigating solidification cracking, thereby offering potential enhancements in the fabrication of high-strength aluminum alloys. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024.