MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Influence of Ion-Irradiation on Hardness Change in Type 304 Stainless Steel Weldment Containing Delta(δ) Ferrite
Se-Hwan ChiYong-Kwan ShinGen-Chan KimYoung-Jig KimJun-Hwa Hong
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2002 Volume 43 Issue 4 Pages 627-632

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Abstract

Differences of high energy-ion induced microstructure of bcc δ-ferrite and fcc austenite matrix, and the effects of δ-ferrite on the Vickers micro-hardness (Hv) after irradiation were investigated for Type 304 stainless steel weldments containing two different δ-ferrite contents: ferrite number (FN) 5.5 and 8.5, respectively. Specimens were irradiated to 1.5 dpa with 8 MeV Fe+4 ions using a Tandem Vande-Graff accelerator (flux: 4.3×1010 ion/cm2·s, fluence: 0.83×1015 ion/cm2) at below 60°C. Calculations TRIM 95 showed that a peak damage appeared at 1.5 \\micron in depth with 0.7 \\micron full width at half maximum (FWHM). These results on irradiation-induced defects (IIDs) distribution were confirmed by TEM. Clear differences for the size and number density of IIDs as black dots (size: 5–10 nm) and loops were observed in both the austenitic matrix and δ-ferrite, where the size of IIDs was far larger in the fcc matrix than the bcc δ-ferrite. Hv test results showed that the irradiation hardening of δ-ferrite was about 1.5 times larger than the austenitic matrix. From microstructural observation the increase of the higher Vickers micro-hardness was explained.

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© 2002 The Japan Institute of Metals and Materials
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