Exploring temperature-controlled friction stir powder additive manufacturing process for multi-layer deposition of aluminum alloys

This paper presents preliminary study on multi-layer deposition of aerospace grade Al 6061 alloy by novel friction stir powder additive manufacturing process. Minimum temperature of deposition was in-situ maintained using close loop temperature-controlled system for minimizing thermal gradient in the build direction. Maximum temperature during the deposition was monitored in-situ using pyrometer and thermal imaging camera. Use of a tool with circumferential and radial grooves and continuous external heating facilitated smooth three-layer deposition of Al 6061 alloy with 60% deposition efficiency and 417 degrees C as maximum deposition temperature. Larger value of temperature at deposition zone improved material flowability and deposition quality. Microstructure of multi-layer deposition found to consist of fine sub-grains. Element analysis showed uniform distribution of major alloying elements in it. Phase analysis revealed Al along with Mg2Si hardening precipitates. Tensile strength and microhardness were close to the commercially available wrought AA6061-T4 alloy. It showed ductility with 16% elongation. The presented process is a viable alternative to fusion-based additive manufacturing processes for multi-layer depositions of aerospace grade and other lightweight alloys which are difficult-to-additively-manufacture. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

This paper presents a preliminary study on the multi-layer deposition of aerospace grade Al 6061 alloy using a novel friction stir powder additive manufacturing process. The deposition temperature was controlled using a closed-loop temperature-controlled system to minimize thermal gradients. A tool with circumferential and radial grooves and continuous external heating was used to facilitate a smooth three-layer deposition with a deposition efficiency of 60% and a maximum deposition temperature of 417 degrees C. The higher temperature at the deposition zone improved material flowability and deposition quality. The microstructure of the multi-layer deposition consisted of fine sub-grains, with a uniform distribution of major alloying elements. Phase analysis revealed the presence of Al and Mg2Si hardening precipitates. The tensile strength and microhardness were similar to those of commercially available wrought AA6061-T4 alloy, and the material exhibited ductility with 16% elongation. The presented process offers a viable alternative to fusion-based additive manufacturing processes for the multi-layer deposition of aerospace grade and other difficult-to-manufacture lightweight alloys.