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1. chinaXiv:201703.00586 [pdf]

Estimation of dislocation concentration in plastically deformed FeCrNi alloy by positron annihilation lifetime

Eryang Lu; Xingzhong Cao; Shuoxue Jin; Yihao Gong; Peng Zhang; Runsheng Yu; Baoyi Wang
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Dislocations would be induced after plastic deformation, which might change the mechanical properties of solids. FeCrNi austenitic model alloy and its Mo-diluted alloy were cold rolled with different degree of thickness reduction. Positrons are sensitive to point defects, which are easily trapped and annihilated around the trapping sites. The mean positron lifetimes have been used to estimate the average dislocation concentration in solids. Meanwhile, the trapping efficiency μ was calculated from the lifetime results. The trapping efficiency value is estimated about 3.31×10-7 cm3s-1 for FeCrNi alloy and 3.31×10-7 cm3s-1 for Mo-diluted alloy, respectively. The increment of the hardness value during plastic deformation is related to the increase of the dislocation density and dislocation pile up in solids.

submitted time 2017-03-26 Hits1584Downloads897 Comment 0

2. chinaXiv:201703.00585 [pdf]

Irradiation induced defects by Fe-ion in 316L stainless steel studied by Positron Annihilation Spectroscopy

Xingzhong Cao; Eryang Lu; Shuoxue Jin; Yihao Gong; Yuanchao Hu; Te Zhu; Peng Zhang; Long Wei; Baoyi Wang
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Solution annealed type 316L austenitic stainless steels were irradiated using 2 MeV Fe ions at room temperature. The implanted fluences were 2012 ions/cm2 and 1013 ions/cm2, respectively. Variable mono-energetic positron beam was performed to characterize the evolution of microstructure and irradiation induced defects. Results show that large amount of vacancy defects formed after heavy ion irradiation. In which, some of mono-vacancies might migrate to form small-sized clusters at room temperature. After irradiation, implanted Fe atoms mainly be interstitials atoms, but some Fe atoms might recombine with vacancies due to their high mobility, which could decrease the defect concentration, effectively.

submitted time 2017-03-26 Hits1556Downloads865 Comment 0

3. chinaXiv:201703.00583 [pdf]

Detection of helium in irradiated Fe9Cr alloys by coincidence Doppler broadening of slow positron annihilation

Xingzhong Cao; Te Zhu; Shuoxue Jin; Peng Kuang; Peng Zhang; Eryang Lu; Yihao Gong; Liping Guo; Baoyi Wang
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

An element analysis method, coincidence Doppler broadening spectroscopy of slow positron annihilation, was employed to detect helium in ion irradiated Fe9Cr alloys. Spectra with higher peak to background ratio were recorded using a two-HPGe-detector coincidence measuring system. It means that information in the high-momentum area of the spectra can be used to identify helium in metals. This identification is not entirely dependent on the helium concentration in the specimens, but is related to the structure and microscopic arrangement of atoms surrounding the positron annihilation site. The results of Doppler broadening spectroscopy and transmission electron microscopy show that vacancies and dislocations were formed in ion irradiated specimens. Thermal helium desorption spectrometry was performed to obtain the types of He traps.

submitted time 2017-03-26 Hits1391Downloads801 Comment 0

4. chinaXiv:201703.00580 [pdf]

Helium/hydrogen synergistic effect in reduced activation ferritic/martensitic steel investigated by slow positron beam

Te Zhu; Shuoxue Jin; Liping Guo; Yuanchao Hu; Eryang Lu; Jianping Wu; Baoyi Wang; Long Wei; Xingzhong Cao
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Here, we investigated the irradiation defect in reduced activation ferritic/martensitic steels by slow positron beam. Three ion-irradiation experiments were carried out: (i) He2+ irradiation, (ii) H+ irradiation and (iii) He2+ irradiation followed by H+ irradiation, at temperature 450 oC. The presents of vacancy defects, represented by ?SHe+H parameter, induced by sequential irradiations was larger than the sum of defects, ?SHe parameter + ?SH parameter, caused by single He ions and single H ions. The synergistic effect of He and H was confirmed clearly from the perspective of positron annihilation spectroscopy.

submitted time 2017-03-26 Hits1238Downloads729 Comment 0

5. chinaXiv:201703.00575 [pdf]

Effect of annealing on Cu precipitates in H ion irradiated Fe–0.6%Cu studied by positron annihilation

Shuoxue Jin; Peng Zhang; Eryang Lu; Baoyi Wang; Daqing Yuan; Long Wei; Xingzhong Cao
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Fe–0.6%Cu alloy was irradiated with H ions to 0.1 dpa, and then annealed for 30 min from 150 oC to 500 oC. We focused the evolution of Cu precipitates in irradiated Fe–0.6%Cu alloy after the isochronal annealing from the perspective of positron annihilation. The ΔW parameters after thermal annealing (400 oC and 500 oC) were much larger than that induced by 0.1 dpa H irradiation. Annealing could promote the aggregation of the Cu-vacancy complexes, and form the Cu cluster–vacancies complexes. When the vacancy-like defects recovered around 500 oC, it meant the formation and growing of the defect-free Cu precipitates.

submitted time 2017-03-26 Hits1504Downloads790 Comment 0

6. chinaXiv:201703.00573 [pdf]

Correlation between Cu precipitates and irradiation defects in Fe-Cu model alloys investigated by Positron annihilation spectroscopy

Shuoxue Jin; Peng Zhang; Eryang Lu; Liping Guo; Baoyi Wang; Xingzhong Cao; ?
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

The correlation between Cu precipitates and vacancy-like defects in three Fe-Cu model alloys, Fe-0.15%Cu, Fe-0.3%Cu and Fe-0.6%Cu, irradiated at 400 °C with hydrogen ions at doses from 0.045 to 0.45 dpa, were revealed by positron annihilation spectroscopy. The formation of vacancy-like defects surrounded by tiny Cu precipitates induced the increment of the S and W parameters after irradiation. The peak value of the relative W parameter (ΔW/W), as the high momentum information on Cu precipitates, located in the track region and decreased with irradiation dose increased from 0.045 dpa to 0.45 dpa. The information on high momentum depended on the coverage fraction of the defects by Cu atoms. The effect of the irradiation dose, the irradiation depth and the Cu content on the Cu coverage fraction of the defects has been investigated in the present work

submitted time 2017-03-26 Hits1332Downloads763 Comment 0

7. chinaXiv:201703.00571 [pdf]

Investigation of vacancy-type defects in helium irradiated FeCrNi alloy by slow positron beam

Eryang Lu; Xingzhong Cao; Shuoxue Jin; Peng Zhang; Chunxiong Zhang; Jing Yang; Yaru Wu; Liping Guo; Baoyi Wang; ?
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

The evolution of microstruture for Fe16.7Cr14.5Ni model alloy and 316 stainless steel irradiated with 140 keV He ions were studied by Positron annihilation spectroscopy. The fluences were 1016 and 5016 He ions/cm2. The irradiation temperature was room temperature and 573 K, respectively. The variation of S parameter-incident positron energy profile indicated that large amount of vacancy-type defects formed after He ion irradiation. Meanwhile, helium atoms deposited in bulk and certain amount of He-vacancy complexes were formed. The vacancy-type defects could be the major defects in track region and He-vacancy complexes would be the main defects in cascade region. The vacancy-type defects could migrate and aggregate to form vacancy clusters and even microvoids at elevated temperature irradiation. The diffusion mechanism of helium atoms might be changed at different irradiation temperature.

submitted time 2017-03-26 Hits1488Downloads869 Comment 0

8. chinaXiv:201703.00570 [pdf]

Cu precipitates in hydrogen ion irradiated Fe-0.3%Cu alloy investigated by positron annihilation spectroscopy

Shuoxue Jin; Xingzhong Cao; Peng Zhang; Eryang LU; Liping Guo; RuiSheng Yu; Baoyi Wang
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

The formation of Cu precipitates in Fe-0.3%Cu binary model alloy after hydrogen ion irradiation at 400 was investigated by positron annihilation spectroscopy based on slow positron beam. In order to study the effect of elevated temperature for the Cu precipitates, the annealing treatment at 400 in Fe-0.3%Cu alloy was also investigated. The S-parameters of specimens increased with the irradiation dose increased, especially in the damage peak region. H+ implantation produced a large number of vacancy-type defects in Fe-0.3%Cu alloy. Compared to the unirradiated samples, the irradiated specimens show an overall major increase in W parameter values. Experimental results indicate that Cu precipitates formed easily under lower irradiation dose at elevated temperature. No obvious Cu precipitates formed when Fe-0.3%Cu alloy was annealed for 2h at 400 .

submitted time 2017-03-26 Hits948Downloads578 Comment 0

9. chinaXiv:201703.00529 [pdf]

The evolution of micro defects in He+ irradiated FeCrNi alloy during isochronal annealing

Eryang Lu; Xingzhong Cao; Shuoxue Jin; Chunxiong Zhang; Peng Zhang; Liping Guo; Te Zhu; Yihao Gong; Baoyi Wang; ?
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

In order to study the microstructural evolution of the He+ irradiated FeCrNi model alloy, 140 keV He+ ions were implanted into the specimen with the fluence of 1015 ions/cm2 at room temperature. Positron Annihilation Spectroscopy was used to characterize the evolution of micro defects during isochronal annealing between 423 K and 873 K. The decrease of the S parameter between 573 K and 623 K has been associated to the annihilation of vacancy clusters, which were not trapped by helium atom. While the decline of the S parameter between 773 K and 823 K in the damage region might be caused by the dissociation of HenVm clusters. The dissociated vacancy clusters were unstable and annihilated rapidly, which decreases the concentration of vacancy defects.

submitted time 2017-03-24 Hits982Downloads561 Comment 0

10. chinaXiv:201703.00512 [pdf]

Effect of annealing on VmHn complexes in hydrogen ion irradiated Fe and Fe-0.3%Cu alloys

Peng Zhang; Shuoxue Jin; Eryang Lu; Baoyi Wang; Yongnan Zheng; Daqing Yuan; Xingzhong Cao
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

The effect of annealing on VmHn complexes and Cu precipitate behaviors in hydrogen ion irradiated Fe and Fe-0.3%Cu alloys was investigated by positron annihilation spectroscopy using a slow positron beam. The results of S parameters indicated that the room temperature irradiation was benefit for the formation of the VmHn complex compared to the elevated temperature irradiation. The S-W results confirmed the formation of Cu precipitates in Fe-0.3%Cu even at the irradiation dose of 0.1 dpa. The formation of the evident S value peaks in the damage region after annealing treatment suggested that the VmHn complexes were broken and a larger of hydrogen atoms were escaping. The residual vacancy defects would migrate towards both the surface region and the opposite direction with the increasing annealing temperature.

submitted time 2017-03-23 Hits922Downloads515 Comment 0

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