An Investigation of Metallurgical Factors Which Affect Fracture Toughness of Ultra-High Strength Steels

Abstract

DETERMINED FOR THE LOW ALLOY ULTRA-HIGH STRENGTH STEELS 4130, 4330, 4340, 4140 AND 300-M. Optical metallography, microprobe analysis, and scanning electron microscopy were used to characterize the structure and morphology, while both Charpy V-notch impact tests and plane strain fracture toughness tests were used to determine the fracture properties. The normal commercial heat treatment resulted in the formation of some bainite in all the alloys. MnS inclusions on prior austenite grain boundaries were found to initiate cracks during loading. By increasing the austenitizing temperature to 1200C, the fracture toughness could be increased by at least 60%. For some alloys increasing the severity of the quench in conjunction with the higher austenitizing temperatures resulted in further increases in the fracture toughness, and the elimination of any observable upper bainite. There was no correlation between the Charpy impact test results and the fracture toughness results.

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Document Details

Document Type
Technical Report
Publication Date
May 01, 1973
Accession Number
AD0767270

Entities

People

  • Earl R. Parker
  • Victor F. Zackay
  • William E. Wood

Organizations

  • University of California, Berkeley

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Alloys
  • Chemical Analysis
  • Chemistry
  • Electron Microscopy
  • Electrons
  • Ferrium
  • Impact Tests
  • Materials
  • Materials Science
  • Measurement
  • Mechanical Properties
  • Mechanics
  • Microscopy
  • Scanning Electron Microscopy
  • Solid Solutions
  • Stress Strain Relations
  • Yield Strength

Fields of Study

  • Materials science

Readers

  • Materials Science (Mechanical Engineering).
  • Metallurgy

Technology Areas

  • Microelectronics