High-cycle and very-high-cycle fatigue of an additively manufactured aluminium alloy under axial cycling at ultrasonic and conventional frequencies

Abstract

Along the building direction, the fatigue behavior of an additively manufactured (AM) aluminium (AlSi10Mg) alloy was investigated in high-cycle and very-high-cycle regimes by using conventionally electromagnetic resonance and ultrasonic vibration with axial loading frequencies of ∼110 Hz and ∼20 k ± 500 Hz, respectively. No frequency effect was observed on the resulted fatigue strength and the fractography up to 108 cycles at stress ratio R = –1. All cracks initiated at AM pores and the dominating one prefers shifting from specimen surface to subsurface with growing very-high-cycle fatigue (VHCF) lives. As the tensile mean stress increases, fatigue strength sharply drops in high value regime of R ≥ 0.5 with annihilating VHCF occurrence, and the fatigue limits degrade on a Gerber relation beyond 109 cycles. At last, a fatigue failure map was proposed to directly describe the panorama of specimen lives under different external loads.