Porosity formation mechanisms and fatigue response in Al-Si-Mg alloys made by selective laser melting

Yang, Kun; Rometsch, Paul; Jarvis, Tom; Rao, J. Babu; Cao, Sheng; Davies, Chris; Wu, Xinhua

doi:10.1016/j.msea.2017.11.078

Cited by 194 publications

(74 citation statements)

References 19 publications

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“…The results published by Yang et al [36] appear to be complementary, rather than superimposable, to the outcomes achieved in the present research. In fact, Yang et al did not pre-heat the build platform (they imposed a base plate temperature of 65 • C) and they thermally post-processed the samples.…”

Section: Stress S Isupporting

confidence: 83%

“…Very recently, Yang et al [36] proposed an accurate investigation of the relationship existing between process parameters and porosity development in A357.0 parts. In order to highlight the effects of porosity on the mechanical properties of finished parts, Yang et al compared the fatigue behavior at R = 0.1 with a frequency of 100 Hz of three different kinds of samples, namely (i) as-built samples (no sub-surface porosity removal; no surface finishing); (ii) surface machined samples (no sub-surface porosity removal); and (iii) machined samples without sub-surface porosity.…”

Section: Stress S Imentioning

confidence: 99%

“…A357.0 is a new entry on the market of commercial feedstocks for AM and hence very little is known so far about its properties. In fact, very few papers have been published to date on the production, microstructure, and mechanical properties of A357.0 parts manufactured by L-PBF [32][33][34][35][36]. It is worth noting that such articles are all very recent, since they have been published after 2016, which confirms the growing interest in this new aluminum alloy for L-PBF.…”

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confidence: 97%

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Fatigue Behavior of As-Built L-PBF A357.0 Parts

Bassoli

Denti

Comin

et al. 2018

Metals

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Laser-based powder bed fusion (L-PBF) is nowadays the preeminent additive manufacturing (AM) technique to produce metal parts. Nonetheless, relatively few metal powders are currently available for industrial L-PBF, especially if aluminum-based feedstocks are involved. In order to fill the existing gap, A357.0 (also known as A357 or A13570) powders are here processed by L-PBF and, for the first time, the fatigue behavior is investigated in the as-built state to verify the net-shaping potentiality of AM. Both the low-cycle and high-cycle fatigue areas are analyzed to draw the complete Wohler diagram. The infinite lifetime limit is set to 2 × 10 6 stress cycles and the staircase method is applied to calculate a mean fatigue strength of 60 MPa. This value is slightly lower but still comparable to the published data for AlSi10Mg parts manufactured by L-PBF, even if the A357.0 samples considered here have not received any post-processing treatment.Keywords: additive manufacturing; laser-based powder bed fusion; aluminum; fatigue strength present in AM parts, which may impact the mechanical behavior of finished constructs [3].Originally developed for rapid prototyping, AM is now growing very rapidly in terms of production numbers and economic importance. According to recent estimations, the sale of AM products and services is expected to grow from US $5.2 billion in 2015 to over US $26.5 billion by 2021. If metal AM is considered, according to statistics, 1768 AM systems were sold in 2017, compared to 983 systems in 2016, thus scoring an impressive increase of nearly 80% [4].Standard ISO/ASTM 52900-15 [5], which defines general principles and terminology for AM, groups AM techniques into seven categories, all of which are compatible with polymer feedstocks. However, only three of these processes, including powder bed fusion, direct energy deposition, and sheet lamination, also apply to metals. Among them, powder bed fusion (PBF) is emerging as the most promising one, on account of its flexibility in terms of part design and feedstock availability.In PBF, thermal energy is used to selectively consolidate specific areas of the powder bed, which is a relatively thin layer of fresh powder (typically below 100 µm) evenly distributed on top of the previously consolidated powder layers. The heat input may be supplied by an electron beam, in electron beam melting (EBM), or by a laser beam, in laser-based powder bed fusion (L-PBF). In the latter case, consolidation may rely upon sintering (direct laser sintering, DLS, also known as selective laser sintering, SLS) or complete melting-solidification mechanisms (selective laser melting, SLM) [6]. As a rule, the energy conveyed to the powder bed is enough to affect not only the new powder layer, but also the material underneath, so as to provide interlayer bonding [7].At present, in spite of the increasingly widespread diffusion of AM in the industry, there is still a lack of understanding of the mechanical behavior of materials processed by L-PBF, especially aluminum and its alloys...

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Section: Stress S Isupporting

confidence: 83%

Section: Stress S Imentioning

confidence: 99%

mentioning

confidence: 97%

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Fatigue Behavior of As-Built L-PBF A357.0 Parts

Bassoli

Denti

Comin

et al. 2018

Metals

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“…P2 and P3 specimens were built along two directions, namely XY and Z as defined in Figure 1-a. P2 fatigue test specimens were machined (MA) from the bars in order to overcome the manufacturing gross surface integrity effects, namely the surface roughness and the presence of a population of defects in the subsurface due to edge lasing [5,6]. One bar corresponds to one specimen.…”

Section: Samples Fabricationmentioning

confidence: 99%

Influence of as-built surface and heat treatment on the fatigue resistance of Additively Layer Manufacturing (ALM) AlSi10Mg alloy.

et al. 2018

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This work concerns the fatigue resistance of a AlSi10Mg material produced by additive manufacturing, and more precisely the competition between as built manufacturing surface and as-machined surface on the fatigue resistance. Samples were built by a powder-bed process with an EOS-M280 machine using standard in two configurations (0° and 90°) in order to evaluate the impact of building direction on fatigue life. The impact of as-built surface on fatigue behavior is quantified for each specimen configuration. A T6 heat treatment is performed on samples in order to evaluate the impact of microstructure on fatigue behavior. For each configurations, the S-N curves is determined in as-built and T6 materials with a load ratio R= -1. The fracture surfaces are carefully analyzed in order to determine the critical defect size for each sample. A Kitagawa type diagram representing the fatigue limit as a function of the defect size is derived from these measurements. All the results were compared to those obtained in asmachined samples.

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“…Over the past years, the production of Al-Si alloys by Selective Laser Melting (SLM) has been broadly studied, attempting to understand the relations between process parameters, microstructure, and mechanical properties [1]. Although a serious progress has been made to improve the process, the parts obtained by SLM still contain defects that are impossible to eliminate, which are found to be the main cause of fatigue damage [2][3][4]. Therefore, studying the defect sensitivity of the fatigue resistance is an important matter for these alloys.…”

Section: Introductionmentioning

confidence: 99%

Defect sensitivity in additively manufactured aluminium alloys: contribution of CAD artificial defects

2019

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The prediction of the fatigue resistance of additively manufactured parts is a current issue for the materials and process qualification in aerospace industry. Despite a continuous improvement of AM process, the presence of defects cannot yet be completely avoided, and the latter are still one of the main causes of fatigue damage in AM materials. In this framework, the present work focused on the influence of defects on the uniaxial fatigue behavior of AlSi7Mg0.6 alloy produced by Selective Laser Melting (SLM). Uniaxial fatigue tests have been performed. Fatigue specimens were subjected to a T6 treatment, and then machined in order to avoid the influence of surface roughness. Besides, for some specimens, artificial defects were directly introduced through CAD. The introduction of artificial defects, whose sizes and positions are precisely controlled, aims to provide a proper assessment of defect sensitivity. X-ray tomography was used to characterize both natural and artificial defects. Finite-element calculations of the local stress fields in the vicinity of defects were conducted, accounting for the real defect geometries obtained with CT scans. The application of a non-local multiaxial fatigue criterion then allowed to analyze defect criticity. *

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Porosity formation mechanisms and fatigue response in Al-Si-Mg alloys made by selective laser melting

Cited by 194 publications

References 19 publications

Fatigue Behavior of As-Built L-PBF A357.0 Parts

Fatigue Behavior of As-Built L-PBF A357.0 Parts

Influence of as-built surface and heat treatment on the fatigue resistance of Additively Layer Manufacturing (ALM) AlSi10Mg alloy.

Defect sensitivity in additively manufactured aluminium alloys: contribution of CAD artificial defects

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