Abstract
In this study, the effect of the state of N atoms in a Fe–N alloy, namely, whether N exists as a dissolved atom or as a nitride on void nucleation, growth, and coalescence during tensile testing was examined and the factors dominating local elongation was discussed. Two types of Fe–0.02 mass% N alloy specimens were used; one was heated to the ferritic phase region before water-quenching, while the other was subjected to aging. The local elongation of the water-quenched specimen was lower than that of the aged specimen. Secondary-ion mass spectrometry and electron backscattering diffraction analyses revealed that N atoms were segregated around grain boundaries similarly in both the water-quenched and the aged specimens, while N atoms precipitated as Fe 4 N in the aged specimen. Void nucleation, growth, and coalescence were observed using synchrotron radiation X-ray laminography. In the water-quenched specimen, voids suddenly grew and coalesced before fracture, while in the aged specimen sudden growth and coalescence were suppressed. Nano-indentation hardness measurements showed that the difference in hardness between the regions around the grain boundaries and grain centers was smaller in the aged specimen compared to that in the water-quenched specimen. This result indicated a lower plastic strain gradient around the grain boundaries in the aged specimen. This lower plastic strain gradient in the aged specimen was caused by precipitation of N atoms as Fe 4 N. From these results, it was concluded that the main factor permitting the greater local elongation of the aged specimen was the lower plastic strain gradient around the grain boundaries.
| Original language | English |
|---|---|
| Pages (from-to) | 943-951 |
| Number of pages | 9 |
| Journal | isij international |
| Volume | 58 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - Jan 1 2018 |
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All Science Journal Classification (ASJC) codes
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry
Cite this
Void nucleation, growth, and coalescence observed by synchrotron radiation x-ray laminography during tensile deformation of Fe–0.02 mass% N alloy. / Furukimi, Osamu; Harada, Shun; Mugita, Yasutaka; Aramaki, Masatoshi; Yamamoto, Masayuki; Takeuchi, Akihisa; Takeuchi, Miyuki; Funakawa, Yoshimasa.
In: isij international, Vol. 58, No. 5, 01.01.2018, p. 943-951.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Void nucleation, growth, and coalescence observed by synchrotron radiation x-ray laminography during tensile deformation of Fe–0.02 mass% N alloy
AU - Furukimi, Osamu
AU - Harada, Shun
AU - Mugita, Yasutaka
AU - Aramaki, Masatoshi
AU - Yamamoto, Masayuki
AU - Takeuchi, Akihisa
AU - Takeuchi, Miyuki
AU - Funakawa, Yoshimasa
PY - 2018/1/1
Y1 - 2018/1/1
N2 - In this study, the effect of the state of N atoms in a Fe–N alloy, namely, whether N exists as a dissolved atom or as a nitride on void nucleation, growth, and coalescence during tensile testing was examined and the factors dominating local elongation was discussed. Two types of Fe–0.02 mass% N alloy specimens were used; one was heated to the ferritic phase region before water-quenching, while the other was subjected to aging. The local elongation of the water-quenched specimen was lower than that of the aged specimen. Secondary-ion mass spectrometry and electron backscattering diffraction analyses revealed that N atoms were segregated around grain boundaries similarly in both the water-quenched and the aged specimens, while N atoms precipitated as Fe 4 N in the aged specimen. Void nucleation, growth, and coalescence were observed using synchrotron radiation X-ray laminography. In the water-quenched specimen, voids suddenly grew and coalesced before fracture, while in the aged specimen sudden growth and coalescence were suppressed. Nano-indentation hardness measurements showed that the difference in hardness between the regions around the grain boundaries and grain centers was smaller in the aged specimen compared to that in the water-quenched specimen. This result indicated a lower plastic strain gradient around the grain boundaries in the aged specimen. This lower plastic strain gradient in the aged specimen was caused by precipitation of N atoms as Fe 4 N. From these results, it was concluded that the main factor permitting the greater local elongation of the aged specimen was the lower plastic strain gradient around the grain boundaries.
AB - In this study, the effect of the state of N atoms in a Fe–N alloy, namely, whether N exists as a dissolved atom or as a nitride on void nucleation, growth, and coalescence during tensile testing was examined and the factors dominating local elongation was discussed. Two types of Fe–0.02 mass% N alloy specimens were used; one was heated to the ferritic phase region before water-quenching, while the other was subjected to aging. The local elongation of the water-quenched specimen was lower than that of the aged specimen. Secondary-ion mass spectrometry and electron backscattering diffraction analyses revealed that N atoms were segregated around grain boundaries similarly in both the water-quenched and the aged specimens, while N atoms precipitated as Fe 4 N in the aged specimen. Void nucleation, growth, and coalescence were observed using synchrotron radiation X-ray laminography. In the water-quenched specimen, voids suddenly grew and coalesced before fracture, while in the aged specimen sudden growth and coalescence were suppressed. Nano-indentation hardness measurements showed that the difference in hardness between the regions around the grain boundaries and grain centers was smaller in the aged specimen compared to that in the water-quenched specimen. This result indicated a lower plastic strain gradient around the grain boundaries in the aged specimen. This lower plastic strain gradient in the aged specimen was caused by precipitation of N atoms as Fe 4 N. From these results, it was concluded that the main factor permitting the greater local elongation of the aged specimen was the lower plastic strain gradient around the grain boundaries.
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U2 - 10.2355/isijinternational.ISIJINT-2017-609
DO - 10.2355/isijinternational.ISIJINT-2017-609
M3 - Article
VL - 58
SP - 943
EP - 951
JO - ISIJ International
JF - ISIJ International
SN - 0915-1559
IS - 5
ER -