Evaluation of toughness in AISI 4340 alloy steel austenitized at low and high temperatures

Journal Article · Tue Jun 01 04:00:00 EDT 1976 · Metall. Trans., A; (United States)

DOI:https://doi.org/10.1007/BF02644080· OSTI ID:6850704

Ritchie, R O ^[1]; Francis, B; Server, W L

---

1. Univ. of California, Berkeley

It has been reported for as-quenched AISI 4340 steel that high temperature austenitizing treatments at 1200/sup 0/C, instead of conventional heat-treatment at 870/sup 0/C, result in a two-fold increase in fracture toughness, K/sub Ic/, but a decrease in Charpy impact energy. This paper seeks to find an explanation for this discrepancy in Charpy and fracture toughness data in terms of the difference between K/sub Ic/ and impact tests. It is shown that the observed behavior is independent of shear lip energy and strain rate effects, but can be rationalized in terms of the differing response of the structure produced by each austenitizing treatment to the influence of notch root radius on toughness. The microstructural factors which affect this behavior are discussed. Based on these and other observations, it is considered that the use of high temperature austenitizing be questioned as a practical heat-treatment procedure for ultrahigh strength, low alloy steels. Finally, it is suggested that evaluation of material toughness should not be based solely on K/sub Ic/ or Charpy impact energy values alone; both sharp crack fracture toughness and rounded notch impact energy tests are required.

• OSTI ID: 6850704
• Journal Information: Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 7; ISSN MTTAB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
AUSTENITIC STEELS
CHARPY TEST
CHROMIUM ALLOYS
CORROSION RESISTANT ALLOYS
FRACTURE PROPERTIES
HEAT TREATMENTS
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
STAINLESS STEELS
STEELS
VERY HIGH TEMPERATURE