The influence of inclusion spacing and microstructure on the fracture toughness of the secondary hardening steel AF1410

Journal Article · Wed Jul 01 04:00:00 EDT 1987 · Metall. Trans., A; (United States)

DOI:https://doi.org/10.1007/BF02647195· OSTI ID:7202779

Garrison, Jr, W M; Moody, N R

An approach to the ductile fracture of ultra high strength steels has been evaluated. According to this approach the critical crack tip opening, delta/sub IC/, will scale with X/sub 0/(R/sub V//R/sub I/vertical bar/sub R//sub 0/. X/sub 0/ is an average inclusion spacing and (R/sub V/R/sub I/)vertical bar/sub R//sub 0/ is the void radius divided by the radius of the inclusion nucleating the void evaluated at the average inclusion size. AF1410 was selected to test this approach because it has exceptionally high fracture toughness on aging at 510/sup 0/C and because its toughness varies markedly with aging temperature. The results from this and earlier work showed a linear relationship exists between delta/sub IC/ and X/sub 0/(R/sub V//R/sub I/)vertical bar /sub R//sub 0/ for values of delta/sub IC/ ranging from about 8 ..mu..m to 60 ..mu..m. The values of (R/sub V//R/sub I/)vertical bar /sub R//sub 0/ for AF1410 aged at 425/sup 0/C and 510/sup 0/C differed by a factor of two. Because the yield strengths and work hardening exponents were similar for the two aging temperatures, the difference in (R/sub V/R/sub I/)vertical bar /sub R//sub 0/ was attributed to changes in microstructure. The microstructures at the two aging temperatures differed in type and size of intra-lath carbides. Both the microstructure and inclusion spacing were found to influence the fracture toughness of AF1410. The average inclusion spacing for this heat of AF1410 was the largest of the six steels evaluated with this model. The model suggests that the large inclusion spacing is critical to the high toughness of AF1410 on aging at 510/sup 0/C. This large inclusion spacing results not from an unusually low inclusion volume fraction but from a large average inclusion size.

• Research Organization: Dept. of Metallurgical Engineering and Materials Science, Carnegie Mellon Univ., Pittsburgh, PA (US)
• OSTI ID: 7202779
• Journal Information: Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 18A:7; ISSN MTTAB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101* -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
AGE HARDENING
ALLOYS
CARBIDES
CARBON COMPOUNDS
CRACK PROPAGATION
CRYSTAL STRUCTURE
DUCTILITY
FRACTURE PROPERTIES
HARDENING
HIGH TEMPERATURE
INCLUSIONS
IRON ALLOYS
IRON BASE ALLOYS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NUCLEATION
STEELS
STRUCTURAL CHEMICAL ANALYSIS
TENSILE PROPERTIES