The Effect of Defects on the Fatigue Initiation Process in Two P/M Superalloys.

Abstract

A metallurgical investigation was performed to determine the effect of defect size, shape, and population on the fatigue initiation process in two high strength P/M superalloys, AF-115 and AF2-1DA. The specific alloy heats tested had contrasting defect populations; the AF-115 alloy contained a large population of spherical pores, and a lesser number of elliptical ceramic inclusions and plate-like hafnium oxide inclusions, and the AF2-1DA material contained only a small population of the elliptically shaped inclusions. Strain controlled fatigue tests were performed on uniform section specimens at 760 C, 649 C, and 22 C using both continuously cycling and cyclic dwell waveforms. Microscopic examination of the failed specimens showed that for the high temperature tests there was a transition in the nucleation site of the cracks that caused failure from a surface to a subsurface location as the strain range was reduced. This surface-subsurface transition (SST) occurred at approximately the same strain range for both alloys.

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Document Details

Document Type
Technical Report
Publication Date
Sep 01, 1980
Accession Number
ADA093509

Entities

People

  • Jack M. Hyzak

Organizations

  • Wright Laboratory

Tags

Communities of Interest

  • Air Platforms

DTIC Thesaurus Topics

  • Chemical Analysis
  • Chemistry
  • Crack Propagation
  • Creep
  • Crystal Structure
  • Heat Treatment
  • Materials
  • Materials Laboratories
  • Mechanical Properties
  • Mechanical Working
  • Mechanics
  • Metallurgy
  • Solid Solutions
  • Surface Properties
  • Tensile Properties
  • Tensile Strength
  • Tensile Stress

Fields of Study

  • Materials science

Readers

  • Materials Science and Engineering.
  • Metallurgy
  • Structural Health Monitoring of Composite Structures.