Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113 [electronic resource].
- Washington, D.C. : United States. Dept. of Energy, 1979. and Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Physical Description:
- Pages: 88 : digital, PDF file
- Additional Creators:
- Brown University, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
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- Free-to-read Unrestricted online access
- 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.
- Published through SciTech Connect., 06/01/1979., "coo-3084/67", and Odegaard, T K.
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