Friction-stir welding of ultrafine grained austenitic 304L stainless steel produced by martensitic thermomechanical processing

Sabooni, S.; Karimzadeh, F.; Enayati, M.H.; Ngan, Ahw

doi:10.1016/j.matdes.2015.03.052

“…12c microstructures. It is also not sensitive to small discontinuities in the grain boundaries that are observed in welded [39,40] and deformed [41] steel microstructures. For a physically based definition, the grain size measurement direction should be parallel with the direction of the slip plane in each grain, requiring the utilisation of orientation information in grain size measurement.…”

Section: Discussionmentioning

confidence: 98%

Characterisation of local grain size variation of welded structural steel

Lehto

¹

,

Romanoff

²

,

Remes

³

et al. 2016

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Previously, it has been shown that the grain size distribution plays an important role in the mechanical properties of welded steel. In the previous investigation, the volume-weighted average grain size has been shown to capture the influence of grain size distribution, resulting in a better fitting Hall-Petch relationship between grain size and hardness. However, the previous studies exclude the effects arising from local variation in grain size. In this paper, the grain size measurement methods are extended for the characterisation of the local grain size variation, which is significant for welded joints and can have an adverse effect on mechanical properties. The local gradient of grain size variation and its dependency on measurement direction are considered. In addition, examples of grain size and hardness variation are shown for S355 base metal and two weld metals, and characteristic differences are highlighted and discussed. The coarse-grained areas of a heterogeneous microstructure are found to have lower hardness than fine-grained areas. However, the surrounding microstructure, i.e. local grain size gradient, has an influence on the measured hardness values.

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“…Iako je ograničen na četiri smera merenja, to je i dovoljno za karakterizaciju metala mikrostruktura šava. It is also not sensitive to small discontinuities in the grain boundaries that are observed in welded [39,40] and deformed [41] steel microstructures. For a physically based definition, the grain size measurement direction should be parallel with the direction of the slip plane in each grain, requiring the utilisation of orientation information in grain size measurement.…”

Section: Diskusijamentioning

confidence: 99%

“…Takođe nije osetljiv na male diskontinuitete u granicama zrna koji su primećeni u zavarenim [39,40] i deformisanim [41] mikrostrukturama čelika. Za fizički zasnovanu definiciju, pravac merenja veličine zrna trebalo bi da bude paralelan sa pravcem ravni klizanja u svakom zrnu, zahteva korišćenje informacija o orijentaciji merenja veličine zrna.…”

Section: Diskusijaunclassified

Characterisation of local grain size variation of welded structural steel

Lehto¹,

Romanoff²,

Remes³

et al. 2016

Zavarivanje i zavarene konstrukcije

0

View full text Add to dashboard Cite

Previously, it has been shown that the grain size distribution plays an important role in the mechanical properties of welded steel. In the previous investigation, the volume-weighted average grain size has been shown to capture the influence of grain size distribution, resulting in a better fitting Hall-Petch relationship between grain size and hardness. However, the previous studies exclude the effects arising from local variation in grain size. In this paper, the grain size measurement methods are extended for the characterisation of the local grain size variation, which is significant for welded joints and can have an adverse effect on mechanical properties. The local gradient of grain size variation and its dependency on measurement direction are considered. In addition, examples of grain size and hardness variation are shown for S355 base metal and two weld metals, and characteristic differences are highlighted and discussed. The coarse-grained areas of a heterogeneous microstructure are found to have lower hardness than fine-grained areas. However, the surrounding microstructure, i.e. local grain size gradient, has an influence on the measured hardness values. RezimeRanije je pokazano da distribucija veličine zrna igra važnu ulogu vezanu za mehanička svojstva zavarenog čelika. U prethodnom istraživanju, zapreminski procenjena prosečna veličina zrna je pokazala uticaj distribucije veličine zrna, što je rezultovalo u boljem ispunjenju Hall-Petch-og odnosa između veličine zrna i tvrdoće. Međutim, prethodne studije isključuju učinke koji proizlaze iz lokalnih varijacija u veličini zrna. U ovom radu, metode merenja veličine zrna su proširene na karakterizaciju varijacije lokalne veličine zrna, što je značajno za zavarene spojeve jer mogu imati negativan uticaj na mehanička svojstva. Razmatraju se lokalni gradijent varijacije veličine zrna i njegova zavisnost od smera merenja. Osim toga, primeri veličine zrna i varijacije tvrdoće su prikazani za S355 kao osnovni materijal i dva šava metala, a karakteristične razlike su istaknute i o njima se diskutuje. Za područja krupnozrne heterogene mikrostrukture utvrđeno je da imaju manju tvrdoću od sitnozrnog područja. Međutim, okružujuća mikrostruktura, t.j. gradijent lokalne veličine zrna, ima uticaj na izmerene vrednosti tvrdoće.

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“…The ability to use FSW for joining of high softening-temperature materials has recently been brought to fruition because of the development of specialized tool material [15,16]. The feasibility of FSW for steels, Ti alloys, and Ni-base alloys has been reported to exhibit sound weld joint [17][18][19][20].…”

Section: Accepted Manuscriptmentioning

confidence: 99%