Cyclic behaviour and microstructural evolution of metastable austenitic stainless steel 304L produced by laser powder bed fusion

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68081723%3A_____%2F23%3A00571447" target="_blank" >RIV/68081723:_____/23:00571447 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216305:26210/23:PU148298

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S2214860423001161?via%3Dihub" target="_blank" >https://www.sciencedirect.com/science/article/pii/S2214860423001161?via%3Dihub</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.addma.2023.103503" target="_blank" >10.1016/j.addma.2023.103503</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Cyclic behaviour and microstructural evolution of metastable austenitic stainless steel 304L produced by laser powder bed fusion

Popis výsledku v původním jazyce

It has been documented that the hierarchical character of microstructure produced by laser powder bed fusion (L-PBF) is the key to superior mechanical properties. Especially important is a fine cell microstructure possessing heterogeneous distribution of dislocation density and alloying elements. Despite multiple studies that have investigated the effect of such L-PBF structure on the stress-strain response during monotonic loading, just a few investigations were devoted to cyclic behaviour. The present study delivers an insight into the cyclic behaviour of L-PBF processed metastable austenitic stainless steel 304L and its relation to the observed microstructure evo-lution and strain-induced martensitic transformation (SIMT). The combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations, and feritscope measurements enabled to follow the onset of strain-induced martensite (SIM) nucleation and underlying dislocation microstructure evolution. The cyclic behaviour consisted of initial cyclic softening regardless of subjected strain amplitude. Afterwards, milder cyclic softening or saturation stage followed until a final failure was characteristic for the tests held at low strain amplitudes (e(a) = 0.5%). The third fatigue life stage, cyclic hardening, was recorded during fatigue tests held at e(a) > 0.5%. The excellent cyclic strength of stainless steel 304L is a direct consequence of cell microstructure containing high dislocation density walls and elemental microsegregation, which effectively inhibit dislocation motion. Cyclic softening was linked with cyclic strain localization into slip bands of decreased dislocation density and heavily altered dislocation cell walls. These bands have been observed for the first time in L-PBF-processed metals. This microstructural feature seems to be a variant of persistent slip bands (PSBs), a typical dislocation arrangement observed in conventionally produced materials subjected to cyclic loading. PSBs present the areas of intensive cyclic plasticity where the SIMT preferentially occurs upon further cycling. The increasing a'-martensite volume fraction, accompanied by a formation of intermediate e-martensite and deformation twinning, resulted in recorded cyclic hardening. The martensite nucleation sites are strongly determined by the underlying cell microstructure, in terms of cell walls dislocation density and chemical segregation, which is tightly related to utilized L-PBF process parameters. The present findings indicate a possible opportunity to control the magnitude of the SIMT susceptibility by fine-tuning of the L-PBF process parameters and conse-quently tailoring the cyclic behaviour.

Název v anglickém jazyce

Cyclic behaviour and microstructural evolution of metastable austenitic stainless steel 304L produced by laser powder bed fusion

Popis výsledku anglicky

It has been documented that the hierarchical character of microstructure produced by laser powder bed fusion (L-PBF) is the key to superior mechanical properties. Especially important is a fine cell microstructure possessing heterogeneous distribution of dislocation density and alloying elements. Despite multiple studies that have investigated the effect of such L-PBF structure on the stress-strain response during monotonic loading, just a few investigations were devoted to cyclic behaviour. The present study delivers an insight into the cyclic behaviour of L-PBF processed metastable austenitic stainless steel 304L and its relation to the observed microstructure evo-lution and strain-induced martensitic transformation (SIMT). The combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations, and feritscope measurements enabled to follow the onset of strain-induced martensite (SIM) nucleation and underlying dislocation microstructure evolution. The cyclic behaviour consisted of initial cyclic softening regardless of subjected strain amplitude. Afterwards, milder cyclic softening or saturation stage followed until a final failure was characteristic for the tests held at low strain amplitudes (e(a) = 0.5%). The third fatigue life stage, cyclic hardening, was recorded during fatigue tests held at e(a) > 0.5%. The excellent cyclic strength of stainless steel 304L is a direct consequence of cell microstructure containing high dislocation density walls and elemental microsegregation, which effectively inhibit dislocation motion. Cyclic softening was linked with cyclic strain localization into slip bands of decreased dislocation density and heavily altered dislocation cell walls. These bands have been observed for the first time in L-PBF-processed metals. This microstructural feature seems to be a variant of persistent slip bands (PSBs), a typical dislocation arrangement observed in conventionally produced materials subjected to cyclic loading. PSBs present the areas of intensive cyclic plasticity where the SIMT preferentially occurs upon further cycling. The increasing a'-martensite volume fraction, accompanied by a formation of intermediate e-martensite and deformation twinning, resulted in recorded cyclic hardening. The martensite nucleation sites are strongly determined by the underlying cell microstructure, in terms of cell walls dislocation density and chemical segregation, which is tightly related to utilized L-PBF process parameters. The present findings indicate a possible opportunity to control the magnitude of the SIMT susceptibility by fine-tuning of the L-PBF process parameters and conse-quently tailoring the cyclic behaviour.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

20501 - Materials engineering

Projekt

<a href="/cs/project/GJ19-25591Y" target="_blank" >GJ19-25591Y: Vliv mikrostruktury na únavové vlastnosti vysoce anisotropických nerezavějících ocelí vyrobených pomocí selektivního laserového tání</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2023

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Additive Manufacturing

ISSN

2214-8604

e-ISSN

2214-7810

Svazek periodika

68

Číslo periodika v rámci svazku

APR

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

14

Strana od-do

103503

Kód UT WoS článku

000964248100001

EID výsledku v databázi Scopus

2-s2.0-85150484492