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Title: Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113

Abstract

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 bymore » 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.« less

Authors:
Publication Date:
Research Org.:
Brown Univ., Providence, RI (USA). Div. of Engineering
Sponsoring Org.:
USDOE
OSTI Identifier:
5880711
Report Number(s):
COO-3084/67
TRN: 79-021454
DOE Contract Number:  
EY-76-S-02-3084
Resource Type:
Technical Report
Resource Relation:
Other Information: Thesis
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 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

Citation Formats

Odegaard, T K. Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113. United States: N. p., 1979. Web. doi:10.2172/5880711.
Odegaard, T K. Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113. United States. https://doi.org/10.2172/5880711
Odegaard, T K. Fri . "Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113". United States. https://doi.org/10.2172/5880711. https://www.osti.gov/servlets/purl/5880711.
@article{osti_5880711,
title = {Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113},
author = {Odegaard, T K},
abstractNote = {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.},
doi = {10.2172/5880711},
url = {https://www.osti.gov/biblio/5880711}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1979},
month = {6}
}