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Prof. Upadrasta Ramamurty (Nanyang Technological Univ.) : Strength, ductility, fracture toughness, a…

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댓글 0건 조회 60회 작성일 2024-04-04 11:29

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A detailed understanding of the correlations between the processing, microstructures, and mechanical performance of alloys is a must before they can be deployed for structural applications with a high degree of reliability. Such an understanding, which allows for tailoring of advanced alloys for the targeted performances, is well-established for those manufactured using the conventional route of manufacturing alloys. Moreover, there are several options available for tuning the microstructures in that route. However, some of them—especially microstructural tuning through the judicious selection of the thermo-mechanical processing steps—are not available in additive manufacturing (AM) of metallic components, which offers a number of technological advantages such as near-net shape forming using a single processing step, flexible and on-demand manufacturing, near-zero material loss during fabrication, etc. and hence is being pursued with considerable scientific and technological vigor across the world. However, alloys made with AM techniques such as laser powder bed fusion (LPBF) have substantially finer microstructures (due to rapid solidification) and distinct mesoscale features. As a consequence, their strength is often higher while the ductility is lower, vis-à-vis CM alloys. The meso-structural features, a result of the ‘bottom up’ approach of building components—line-by-line and layer-by-layer with in-situ alloying capability—can impart very high fracture toughness to these alloys. The presence of porosity, which is inevitable given that the feedstock is powder, results in lowered unnotched fatigue resistance. Implications of these in terms of possible directions for designing AM alloys with high mechanical performance will be discussed.

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