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Effect of nitrogen on the dynamic strain ageing behaviour of type 316L stainless steel
No full textThe dynamic strain ageing (DSA) behaviours of type 316L stainless steels containing different nitrogen contents (0.01-0.15 wt% N) were studied in tension under varying strain rates (1 x 10(-2)-2 x 10(-4) s(-1)) and the test temperatures (R.T -1023 K). The temperature range for DSA was moved to higher temperature for increasing nitrogen contents. The critical strain, ec for the onset of serration increased with nitrogen content at 773 K and then became almost constant at 873 K. Type A and B serrations were observed at 873 K with the value of the strain required to effect the transition from type A to type B serration increasing for nitrogen contents up to 0.1 wt% and then becoming saturated. The activation energy for DSA was 23.4-26.2 kcal mol(-1) (97.8-109.5 kJ mol(-1)) at the onset and 65.0-76.6 kcal mol(-1) (271-320.2 kJ mol(-1)) at the end of serration. The lower activation energy was related to vacancy diffusion and the higher activation energy was attributed to the diffusion of chromium to dislocations. The activation energy for DSA was slightly increased with nitrogen addition. DSA was retarded by an increase in the nitrogen content since nitrogen reduced the chromium diffusion to dislocations due to a strong interaction between the nitrogen and chromium. (C) 1998 Chapman & Hall
Effect of nitrogen on high temperature low cycle fatigue behaviors in type 316L stainless steel
No full textStrain-controlled low cycle fatigue (LCF) tests were conducted in the temperature range of RT-600 degrees C and air atmosphere to investigate the nitrogen effect on LCF behavior of type 316L stainless steels with different nitrogen contents (0.01-0.15%). The waveform of LCF was a symmetrical triangle with a strain amplitude of +/- 0.5% and a constant strain rate of 2 x 10(-3)/s was employed for most tests. Cyclic stress response of the alloys exhibited a gradual cyclic softening at RT, but a cyclic hardening at an early stage of fatigue life at 300-600 degrees C. The hardening at high temperature was attributed to dynamic strain aging (DSA). Nitrogen addition decreased hardening magnitude (maximum cyclic stress - first cyclic stress) because nitrogen retarded DSA for these conditions. The dislocation structures were changed from cell to planar structure with increasing temperature and nitrogen addition by DSA and short range order (SRO), Fatigue life was a maximum at 0.1% nitrogen content, which was attributed to the balance between DSA and SRO. (C) 1998 Elsevier Science B.V
Integrity of Ni-base superalloys for advanced nuclear systems application - environment and materials interaction
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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