Effect of austenitizing temperature upon the microstructure and mechanical properties of experimental Fe/Cr/C and Fe/Cr/C/Ti steels
Increasing the austenitizing temperature from 870/sup 0/C to 1100/sup 0/C and higher can increase the fracture toughness, K/sub Ic/, of common high strength structural steels from 50 to 100% with no loss in strength. However, the ductility (% reduction in area from a tensile test) decreases by as much as a factor of 3, and the Charpy impact energy either decreases or remains constant. The trend of increasing fracture toughness and decreasing Charpy impact energy appears to be inconsistent, but has been rationalized by considering the interaction of the stress field as a function of notch root radius and the microstructure. The present study investigates the as-quenched strength and toughness of simple Fe/Cr/C alloys with and without titanium as a function of austenitizing temperature. For the ternary Fe/Cr/C alloys the results are consistent with earlier investigations, but the fracture toughness does not change with increasing austenitizing temperatures after 0.2 wt % Ti is added. The titanium forms carbides (TiC) that did not dissolve, providing a roughly constant number of crack nucleation sites, and preventing austenite grain growth up to 1100/sup 0/C. The differences in mechanical behavior, particularly the rounded notch toughness, are discussed and explained in terms of the microstructural characteristics of the alloys.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6534592
- Report Number(s):
- LBL-7670
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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