Loss of Fracture Resistance in High Carbon Steel Due to Non-Martensitic Phases.
Abstract
Attempts to control the dynamic compression failure modes of tungsten fiber reinforced steel matrices included changing the matrix material from mild steel to a hypereutectoid steel. However, the thermo-mechanical processes used to fabricate such metal matrix composite materials produce mixed microstructures, and it was not known to what extent the nonmartensitic transformation products influence mechanical behavior. This work examines the effects of isothermally transformed pearlite, bainite, and cementite on the strength, ductility, and plane-strain fracture toughness of a hypereutectoid silico-manganese steel that typifies the compositions being evaluated for a class of metal matrix composite systems. The small-grained, quenched-and-tempered martensite was the toughest material (60 MPa sq. root of m). Increasing the pearlite content gradually decreased the fracture toughness. However, increasing the banite content by even slight amounts produced a catastrophic decrease in fracture toughness to half that value, which was found to be nearly the minimum KIC determined from low temperature (-54C) tests, i.e., 28 MPA sq. root of m. This result dramatizes the importance of careful heat treatment when using such materials in engineering structures. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 05, 1979
- Accession Number
- ADA072051
Entities
People
- Changyoung Kim
- R. J. Weimer
- W. L. Phillips
Organizations
- United States Naval Research Laboratory