INFLUENCE OF ROUGH AS-BUILT SURFACES ON SMOOTH AND NOTCHED FATIGUE BEHAVIOR OF L-PBF AlSi10Mg

Abstract

Near-net shape metal parts of great geometrical complexity are fabricated by the Laser Powder Bed Fusion (L-PBF) technology directly from a CAD model. Therefore, parts can be lightweight, less expensive in terms of material use and with shapes that may be impossible to produce by conventional technology. The fatigue behavior of L-PBF part in as-built condition is negatively affected by poor surface quality. Surface finishing after fabrication may be either unacceptably costly or impossible because the surface is inaccessible. Fatigue performance can be further reduced by the notch effect due to local geometrical variations. Among the Al-alloys, AlSi10Mg is readily processed with L-PBF and it is of interest for different industrial sectors.In this contribution two aspects, that is: i) the directional smooth fatigue behavior of as-built AlSi10Mg, and ii) the notch fatigue behavior with as-built surfaces are investigated. Eight sets of un-notched and notched miniature specimens of AlSi10Mg were produced as a single batch by L-PBF and tested in the as-build state under cyclic plane bending loading. The smooth fatigue behavior was determined as very sensitive to applied stress direction with respect to the build direction. The directional nature of the fatigue behavior was confirmed by notch fatigue data. Therefore, four notch fatigue factors that depend on the PBF technology were introduced and determined. The fatigue behavior of L-PBF AlSi10Mg obtained here was compared satisfactorily against recent data obtained with standard specimen geometries and test methods. The present methodology using mini specimens under cyclic bending efficiently determines the fatigue response of L-PBF metals.