VHCF Response up to 109 Cycles of SLM AlSi10Mg Specimens Built in a Vertical Direction

Davide S Paolino,Jacopo Fiocchi,Massimo Rossetto,Ausonio Tuissi,Andrea Tridello,Giorgio Chiandussi,Carlo A Biffi

doi:10.3390/app9152954

Abstract

It is well-known that many manufacturing parameters affect the quasi-static and the fatigue response of additive manufacturing (AM) parts. In particular, due to the layer-by-layer production, the load orientation, with respect to the building direction, plays a fundamental role for the fatigue response. This paper investigates the fatigue response up to 109 cycles (very high cycle fatigue (VHCF)) of selective laser melting (SLM) AlSi10Mg specimens built in a vertical direction. Ultrasonic tension-compression tests (stress ratio of –1) are carried out on as-built Gaussian specimens with a large loaded volume (2300 mm3). Fracture surfaces are investigated with the scanning electron microscope to analyze the defects originating the VHCF failure. Probabilistic S-N curves are estimated and analyzed. Experimental results confirm that the defect size controls the VHCF response, thus highlighting the importance of testing large risk volumes for a reliable assessment of VHCF behavior. The average value of the VHCF strength is close to that of the hourglass specimen tested in the literature. The variability of the VHCF strength is instead significantly larger, due to the scattered size distribution of the defects located near the specimen surface, which is the most critical region for crack initiation.

Highlights

In the last few years, the use of components produced through additive manufacturing (AM)processes is rapidly growing in many industrial applications
The AMed microstructure of Al-Si alloys obtained by selective laser melting (SLM) or laser metal wire deposition [9] consists of an interconnected Al-Si eutectic structure, with small grains distributed inside superimposed melt pools
AlSi10Mg specimens built in a vertical direction and tested above available in the literature for AlSi10Mg specimens built in a vertical direction and tested above 10 specimen typeifand post-treatment after the AM building different in [22], cycles

Summary

Introduction

In the last few years, the use of components produced through additive manufacturing (AM)processes is rapidly growing in many industrial applications. AM parts are currently employed in applications subjected to static loads at room and high temperature [1,2], such as brackets [3], medical devices [4], or heat exchangers [5]; their use is still limited for applications subjected to fatigue loads [6,7]. The resulting microstructure of Al-Si produced by AM is much finer than the microstructure obtained by conventional casting, thanks to the high cooling rates associated to the solidification of a limited liquid pool during the layer-by-layer manufacturing. The AMed microstructure of Al-Si alloys obtained by selective laser melting (SLM) or laser metal wire deposition [9] consists of an interconnected Al-Si eutectic structure, with small grains distributed inside superimposed melt pools

Objectives

Methods

Results

Conclusion