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Low cycle fatigue behavior and failure mechanisms of additively manufactured Ti-6Al-4V

  • Despite of the significant advances in AM process optimization there is still a lack of experimental results and understanding regarding the mechanical behavior and microstructural evolution of AMparts, especially in loading conditions typical for safety-relevant applications e.g. in the aerospace or power engineering. Within the scope of the presented investigations, a characterization of the fatigue behavior of additively manufactured Ti-6Al-4V in the low cycle fatigue regime was carried out in the range of 0.3 to 1.0 % strain amplitude at room temperature, 250°C and 400°C. The Ti-6Al-4V specimens are machined out of lean cylindrical rods, which were fabricated using powder laser metal deposition (LMD) with an improved build-up strategy. The improved strategy incorporates variable track overlap ratios to achieve a constant growth in the shell and core area. The low-cycle-fatigue behavior is described based on cyclic deformation curves and strain-based fatigue life curves. TheDespite of the significant advances in AM process optimization there is still a lack of experimental results and understanding regarding the mechanical behavior and microstructural evolution of AMparts, especially in loading conditions typical for safety-relevant applications e.g. in the aerospace or power engineering. Within the scope of the presented investigations, a characterization of the fatigue behavior of additively manufactured Ti-6Al-4V in the low cycle fatigue regime was carried out in the range of 0.3 to 1.0 % strain amplitude at room temperature, 250°C and 400°C. The Ti-6Al-4V specimens are machined out of lean cylindrical rods, which were fabricated using powder laser metal deposition (LMD) with an improved build-up strategy. The improved strategy incorporates variable track overlap ratios to achieve a constant growth in the shell and core area. The low-cycle-fatigue behavior is described based on cyclic deformation curves and strain-based fatigue life curves. The lifetimes are fitted based on the Manson-Coffin-Basquin relationship. A characterization of the microstructure and the Lack-of-Fusion (LoF)-defect-structure in the as-built state is performed using optical light microscopy and high-resolution computed tomography (CT) respectively. The failure mechanism under loading is described in terms of LoF-defects-evolution and crack growth mechanism based on an interrupted LCF test with selected test parameters. After failure, scanning electron microscopy, digital and optical light microscopy and CT are used to describe the failure mechanisms both in the longitudinal direction and in the cross section of the specimens. The fatigue lives obtained are comparable with results from previous related studies and are shorter than those of traditionally manufactured (wrought) Ti-6Al-4V. In this study new experimental data and understanding of the mechanical behavior under application-relevant loading conditions (high temperature, cyclic plasticity) is gained. Furthermore, a better understanding of the role of LoFdefects and AM-typical microstructural features on the failure mechanism of LMD Ti-6Al-4V is achieved.zeige mehrzeige weniger

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Metadaten
Autor*innen:Luis Avila
Koautor*innen:Birgit Rehmer, Birgit Skrotzki, B. Graf, Michael Rethmeier, Alexander Ulbricht
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2019
Organisationseinheit der BAM:5 Werkstofftechnik
5 Werkstofftechnik / 5.2 Metallische Hochtemperaturwerkstoffe
8 Zerstörungsfreie Prüfung
8 Zerstörungsfreie Prüfung / 8.5 Röntgenbildgebung
9 Komponentensicherheit
9 Komponentensicherheit / 9.3 Schweißtechnische Fertigungsverfahren
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Additive Manufacturing; Computed Tomography; High Temperature Testing; Low Cycle Fatigue; Microstructure; Tensile Properties; Ti-6Al-4V; Titanium
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Additive Fertigung
Material / Degradation von Werkstoffen
Veranstaltung:First European Conference on Structural Integrity of Additively Manufactured Materials (ESIAM19)
Veranstaltungsort:Trondheim, Norway
Beginndatum der Veranstaltung:09.09.2019
Enddatum der Veranstaltung:11.09.2019
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:06.11.2019
Referierte Publikation:Nein
Eingeladener Vortrag:Nein
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