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Hall–Petch Behavior in Ultra-Fine-Grained AISI 301LN Stainless Steel

“…In this fashion, a k value of~274 MPa lm 1/2 and an offset stress of 252 MPa were calculated. These values differ considerably from those obtained by Schino et al [5,11] for AISI 301 SS and AISI 304 SS. In particular, these investigations reported higher k values (~400 MPa lm 1/2 ) for both SS and a deviation from the HallPetch relationship for AISI 301 SS below a grain size of 3 lm.…”

“…However, calculations using " d yields a value of k~290 MPa lm 1/2 that is still significantly less than those reported in the literature. [5,11] Thus, we believe that there may be fundamental reasons, other than grain size, that may be responsible for a low k value. Possible reasons may include (1) the presence of retained tempered martensite after annealing, which was not considered by Schino et al; [5,11] (2) the presence of nitrogen in AISI 301LN SS, which has a different strengthening effect from that of carbon, which is present in AISI 301 SS and AISI 304 SS; and (3) the formation of CrN nitrides in AISI 301LN SS, instead of carbides, that may be present in AISI 301 SS and AISI 304 SS.…”

“…According to Shino et al, [11] the Hall-Petch relation seemed to break down below 3-lm grain size for AISI 301 SS. However, these investigations [5,11] did not seem to consider the fact that metastable austenitic SS do not fully convert the stress-induced martensite to reverted austenite during annealing, particularly at low annealing temperatures. Hence, the presence of martensite in annealed samples will influence the yield strength, which consequently will affect the Hall-Petch behavior.…”

“…[10] In order to better understand the interplay between fine austenite grain size and the mechanical properties obtained, it is thus important to determine the HallPetch relation in these ultra-fine-grained SS. Shino et al [5,11] has reported a Hall-Petch type behavior for AISI 304 SS and AISI 301 SS down to 0.8-and 3-lm grain size, respectively. According to Shino et al, [11] the Hall-Petch relation seemed to break down below 3-lm grain size for AISI 301 SS.…”

“…Shino et al [5,11] has reported a Hall-Petch type behavior for AISI 304 SS and AISI 301 SS down to 0.8-and 3-lm grain size, respectively. According to Shino et al, [11] the Hall-Petch relation seemed to break down below 3-lm grain size for AISI 301 SS. However, these investigations [5,11] did not seem to consider the fact that metastable austenitic SS do not fully convert the stress-induced martensite to reverted austenite during annealing, particularly at low annealing temperatures.…”