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An innovative approach to build a high-performance, thermally stable Al-8Ce-10Mg (wt.%) alloy via friction-stir based solid-state additive manufacturing, called additive friction stir deposition, has been demonstrated in this study. The deposited material displayed 22% higher yield strength and 181% improvement in ductility as compared to the base material. The deposit also exhibited excellent tensile properties at elevated temperatures. The improved performance has been attributed to multiple strengthening mechanisms active in the built component. Al-Ce particle fragmentation, grain refinement, and retention of Mg in solid solution during the process synergistically resulted in the improved mechanical performance. The fragmentation of Al11Ce3 particles occurred due to intense frictional heating and shearing during the process. Scanning electron microscopy, nanoindentation, tensile testing, differential scanning calorimetry, and X-ray diffraction analysis were used to establish process-structure-property correlations at multiple length scales.
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INTRODUCTION
Additive manufacturing (AM) has gained research thrust in the quest to achieve sustainable manufacturing. Conventional fusion-based metal AM processes, such as powder bed fusion and directed energy deposition, have been hot topics of research in recent years.1 These processes are advantageous in the production of functionallyand geometrically-sophisticated parts. However, the conventional fusion-based AM processes face challenges, like low rate of manufacturing, high cost of production, intricacies of process control for defect elimination, stringent quality regulations on (powder) raw material, large thermal gradients that lead to anisotropic properties, and residual stresses.2
A relatively new solid-state process called additive friction stir deposition (AFSD), a promising development in the AM domain, is less complex from the process control standpoint.3 Process variables, such as tool rotation rate (x), tool traverse speed (V), and material feed rate (F), provide a larger operating window to produce defect-free components compared to conventional fusion AM methods, whose optimum operating range is confined by lack of fusion and keyhole porosity. Moreover, the components obtained exhibit isotropic properties and possess refined equiaxed grains. The wrought microstructure of the deposit obtained by AFSD results in enhanced properties, compared to the solidification-induced microstructure in conventional fusion-based AM material. Being a high throughput process to produce bulk components, AFSD is rapidly growing as a promising solid-state AM technique. Despite numerous advantages of AFSD such as energy efficiency, near defect-free build capability, high scalability, wrought...