Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113
Correlations between the microstructure of an ultra-high strength steel and material resistance to fracture, as measured by blunt notch Charpy impact tests and sharp crack K/sub IC/ tests, were investigated for a standard 870/sup 0/C/oil and an experimental 1175/sup 0/C/oil austenitizing treatment. The increase in sharp crack toughness with higher temperature austenitizing treatments, for the as-quenched and 200/sup 0/C/oil temper conditions, was rationalized by a fracture criterion based on the notion that for fracture to occur, a critical strain, epsilon/sub f/, must be achieved over some critical distance, delta. The lath colonies were identified as the fracture controlling microstructural unit, and hence, their size was considered to be the critical distance, delta. Toughness in the 300/sup 0/C/l hour and 400/sup 0/C/l hour temper conditions, for which the mechanical data indicated an embrittlement, was clearly controlled by the cementite morphology in conjunction with the prior austenite grain size. Attempts to rationalize toughness in these temper conditions, using a stress-controlled fracture criterion, were unsuccessful and led to physically unreasonable results. In the 500/sup 0/C/l hour temper condition, stable crack growth and periodic ridge patterns were observed. Fracture toughness differences between the 870/sup 0/C and 1175/sup 0/C austenitizing treatments were qualitatively rationalized by the nature of the respective fracture morphologies. Good correspondence between J/sub IC/ and the so-called tearing modulus, T, as indicators of sharp crack fracture toughness, was observed.
- Research Organization:
- Brown Univ., Providence, RI (USA). Div. of Engineering
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- EY-76-S-02-3084
- OSTI ID:
- 5880711
- Report Number(s):
- COO-3084/67; TRN: 79-021454
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
Similar Records
Evaluation of toughness in AISI 4340 alloy steel austenitized at low and high temperatures
Effect of heat treatment on microstructure and cryogenic fracture properties in 5Ni and 9Ni steel
Related Subjects
STEELS
FRACTURE PROPERTIES
MICROSTRUCTURE
AUSTENITE
CHARPY TEST
CHEMICAL COMPOSITION
CRACKS
CRYSTAL STRUCTURE
HEAT TREATMENTS
PRECIPITATION
RUPTURES
STRAINS
TEMPERATURE EFFECTS
TEMPERING
TENSILE PROPERTIES
TESTING
VERY HIGH TEMPERATURE
YIELD STRENGTH
ALLOYS
CARBON ADDITIONS
FAILURES
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
SEPARATION PROCESSES
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties