Effect of Surface and Subsurface Defects on Fatigue Behavior of AlSi10Mg Alloy Processed by Laser Powder Bed Fusion (L-PBF)

Milad Hamidi Nasab,Alessandro Giussani,Valeria Tirelli,Maurizio Vedani,Dario Gastaldi

doi:10.3390/met9101063

Abstract

The fatigue behaviour of an AlSi10Mg alloy processed by laser powder bed fusion (L-PBF) and subjected to different surface finishing processes was investigated paying special attention to the residual defects on the surface and the dominant fatigue failure mechanisms. Roughness measurements and qualitative surface morphology analysis showed smooth surfaces in the case of vibro-finishing and machining followed by polishing. The fatigue performance did not reveal to be directly related to surface roughness, but residual intrusions left on the finished surfaces. Post-mortem analysis showed single- or multiple-crack nucleation from pores opened on the surface, un-melted powders, or spatters considered as typical L-PBF defects. A fatigue limit of 195 MPa for machined and polished samples was obtained by substantial removal of surface and subsurface defects.

Highlights

Metal additive manufacturing (AM) enables the fabrication of geometrically complex shapes providing structural parts for various industrial fields such as in medical, automotive, and aerospace sectors
Higher magnification primary views (Figure the presence of a fine cellular solidification consisting in submicrometric α-Al2b,c) cellsreveal decorated by a network of Si
The data collected for the SB samples in this study reveal that, the reduction of average roughness was fairly limited when compared to as-built samples, the achieved fatigue strength was comparable to that of VF series in the low-cycle fatigue (LCF) regime, and superior to it in the high-cycle fatigue HCF regime

Summary

Introduction

Metal additive manufacturing (AM) enables the fabrication of geometrically complex shapes providing structural parts for various industrial fields such as in medical, automotive, and aerospace sectors. While monotonic properties of additively manufactured parts have been widely investigated and a detailed frame of information is available from open literature, fatigue behavior still deserves research efforts to gain a full understanding about all its variables of influence [1,3,4,5,6,7]. It is well known that fatigue properties are inherently affected by a significant scatter. This statistical variability is amplified in AM products due to the presence of both internal and surface-related defects

Methods

Results

Discussion

Conclusion