Atom Probe Tomography Examination of Carbon Redistribution in Quenched and Tempered 4340 Steel
- Los Alamos National Laboratory
- ORNL
Quenching and tempering produces a wide range of mechanical properties in medium carbon, low alloyed steels - Study fragmentation behavior as a function of heat-treatment. Subtle microstructural changes accompany the mechanical property changes that result from quenching and tempering - Characterize the location and distribution of carbon and alloying elements in the microstructure using atom probe tomography (APT). Perform complementary transmission electron microscopy (TEM). Tempering influences the mechanical properties and fragmentation of quenched 4340 (hemi-shaped samples). APT revealed carbon-enriched features that contain a maximum of {approx}12-14 at.% carbon after quenching to RT (the level of carbon is perhaps associated with the extent of autotempering). TEM confirmed the presence of twinned martensite and indicates {var_epsilon} ({eta}) transition carbides after oil quenching to RT. Tempering at 325 C resulted in carbon-enriched plates (> 25 at.% C) with no significant element partitioning (transition carbides?). Tempering at 450 C and 575 C resulted in cementite ({approx} 25 at.% C) during late stage tempering; Cr, Mn, Mo partitioned to cementite and Si partitioned to ferrite. Tempering at 575 C resulted in P segregation at cementite interfaces and the formation of Cottrell atmospheres.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- DOE/LANL
- DOE Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1048370
- Report Number(s):
- LA-UR-12-23903; TRN: US201216%%909
- Resource Relation:
- Conference: ShaRE Peer Review Meeting at Oak Ridge National Laboratory ; 2012-08-08 - 2012-08-09 ; Oak Ridge, Tennessee, United States
- Country of Publication:
- United States
- Language:
- English
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