Structure-property relations and the design of Fe-4Cr-C base structural steels for high strength and toughness

Journal Article · Sat Mar 01 04:00:00 EST 1980 · Metall. Trans., A; (United States)

OSTI ID:5534033

Narasimha Rao, B V ^[1]; Thomas, G

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1. General Motors Technical Center, Warren, MI

Some design guidelines for improving strength-toughness combinations in medium carbon structural steels are critically reviewed. From this, quaternary alloy development based on Fe/Cr/C steels with Mn or Ni additions for improved properties is described. Transmission electron microscopy and x-ray analysis reveal increasing amounts of retained austenite in these alloys with Mn content up to 2 wt % and Ni additions at 5 wt % after quenching from 1100/sup 0/C. A corresponding improvement in toughness properties is also found. Grain refining results in a further increase in the amount of retained austenite. In addition, the excellent combinations of strength and toughness in these quaternary alloys are attributed to the production of dislocated lath martensite from a homogeneous austenite phase free from undissolved alloy carbides. The question of thermal instability of retained austenite following tempering is considered in detail and it is shown that the decomposition of retained austenite is closely related to the ease of nucleation and growth of cementite. Thus, graphitizing alloying elements such as Ni are beneficial in postponing the decomposition of retained austenite. 15 figures, 4 tables.

• OSTI ID: 5534033
• Journal Information: Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 11; ISSN MTTAB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
AUSTENITE
CARBON ADDITIONS
CARBON STEELS
CHROMIUM ALLOYS
COHERENT SCATTERING
DIFFRACTION
ELECTRON MICROSCOPY
FRACTURE PROPERTIES
IRON ALLOYS
IRON BASE ALLOYS
MANGANESE ADDITIONS
MANGANESE ALLOYS
MECHANICAL PROPERTIES
MICROSCOPY
MOLECULAR STRUCTURE
NICKEL ADDITIONS
NICKEL ALLOYS
SCATTERING
STEELS
X-RAY DIFFRACTION