Accession Number : ADA114712

Title :   Direct Studies of Fracture Mechanisms in Metals at Highest Magnification.

Descriptive Note : Final rept. 1 Feb 69-28 Feb 82,


Personal Author(s) : Wilsdorf,H G F

PDF Url : ADA114712

Report Date : May 1982

Pagination or Media Count : 67

Abstract : Techniques for in-situ straining to fracture were developed for use in high voltage and conventional transmission electron microscopes in order to record the dynamical features preceding crack initiation and subsequent crack propagation in ductile metals. Eight pure metals and alloys have been investigated. It was discovered that dislocation cell walls are the primary sites for microcrack initiation, even in alloys which contain soft second phase particles. Ligament fracture was found to occur by shear which, in low stacking fault metals, was by translation and twinning. The presence of micro-voids and cell wall remnants affected the zig-zag geometry of the crack flank. For macroscopic rupture and for cup-and-cone fracture, the final separation took place by rupture processes in the microstructural regime. (Author)

Descriptors :   *Metals, *Steel, *Aluminum alloys, *Fracture(Mechanics), *Crack propagation, Magnification, Ductility, Rupture, Electron microscopy, Electronic scanners, Plastic deformation, Stress strain relations, X ray diffraction, Whisker composites

Subject Categories : Physical Chemistry
      Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE