Characterization of tempered martensite microstructure and embrittlement by acoustic and/magnetic Barkhausen signal measurement

Journal Article · Thu Sep 01 00:00:00 EDT 1988 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/S0036-9748(88)80025-5· OSTI ID:6050548

Kameda, J

It has been well recognized that ultrahigh strength alloy steels exhibit embrittlement when they are tempered in the temperature range from 300 to 400/sup 0/C. This phenomenon is referred to as tempered martensite embrittlement. The mechanism for tempered martensite embrittlement has been extensively studied by many investigators. Tempered martensite embrittlement is attributed to the occurrence of intergranular and/or cleavage fracture. The fracture mode depends on the alloy composition and the impurity content of steels. The intergranular embrittlement is caused by two events: segregation of impurities such as sulfur and phosphorus, and carbide precipitation at grain boundaries. The intergranular segregation of impurities during austenitization weakens grain boundaries and the precipitation of carbides during tempering promotes the nucleation and propagation of cracks. A major cause for tempered martensite embrittlement associated with cleavage fracture is the tramsformation of retained austenite at martensite lath boundaries to form coarse carbides. For both cases, the concurrent occurrence of softening and carbide precipitation, which mitigates and enhances embrittlement effects, respectively, gives rise to a toughness trough during tempering treatments. Therefore, it is important to investigate nondestructively the evolution of tempered martensite microstructure which causes embrittlement. The objective of this study is to evaluate nondestructively the characteristics of tempered martensite microstructure and embrittlement in an ultrahigh strength steel by measuring the two types of Barkhausen signals.

• Research Organization: Ames Lab., Iowa State Univ., Ames, IA (US)
• OSTI ID: 6050548
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Vol. 22:9; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
42 ENGINEERING
420500 -- Engineering-- Materials Testing
ACOUSTIC MEASUREMENTS
ALLOYS
AUSTENITIC STEELS
CARBIDES
CARBON ADDITIONS
CARBON COMPOUNDS
CHEMICAL REACTIONS
CORROSION
CRYSTAL STRUCTURE
ELEMENTS
EMBRITTLEMENT
GRAIN BOUNDARIES
HEAT TREATMENTS
IMPURITIES
INTERGRANULAR CORROSION
IRON ALLOYS
IRON BASE ALLOYS
MAGNETIC FIELDS
MARTENSITE
MATERIALS TESTING
MICROSTRUCTURE
NONDESTRUCTIVE TESTING
NONMETALS
PHOSPHORUS
PRECIPITATION
SEPARATION PROCESSES
STEELS
SULFUR
TESTING