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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.43  No.4 (2002)  >  pp.627-632

MATERIALS TRANSACTIONS
<<Previous article Vol.43  No.4 (2002)   pp.627 - 632 Next article>>

Influence of Ion-Irradiation on Hardness Change in Type 304 Stainless Steel Weldment Containing Delta(δ) Ferrite

Se-Hwan Chi1), Yong-Kwan Shin2), Gen-Chan Kim1), Young-Jig Kim3) and Jun-Hwa Hong1)
1) Nuclear Materials Development Team, Korea Atomic Energy Research Institute
2) Transmission Production Team, Hyundai Power Tech.
3) Department of Advanced Materials Engineering, Sungkyunkwan University


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.


Keyword:
irradiation effects, delta(δ) ferrite, austenitic stainless steels, dislocation loops, ferrite number, accelerator irradiation

Received: October 15, 2001
Accepted: March 06, 2002 , Published online: September 06, 2005
Copyright (c) 2005 The Japan Institute of Metals

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