Accession Number : AD0486738

Title :   TRANSMISSION ELECTRON MICROSCOPIC STUDY OF PRECIPITATION IN A TITANIUM-COPPER ALLOY.

Descriptive Note : Technical rept. Oct 64-Mar 66,

Corporate Author : AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OH

Personal Author(s) : Fujishiro, Shiro ; Gegel, Harold L.

Report Date : MAY 1966

Pagination or Media Count : 34

Abstract : The morphology of the precipitates in a Ti-0.5 weight percent Cu alloy has been observed by means of transmission electron microscopy with particular attention being given to the defect structure of the matrix prior to the precipitation. It was found that introduction of point defects by deforming the quenched specimen at liquid N2 temperature prior to annealing yielded a high density of very fine precipitates in the matrix, whose diameter ranged from 50 to 100 A. In order to interpret this fact the role of vacancy-solute complexes was emphasized on the nucleation and growth at the initial stage of precipitation. In slow-cooled specimens from the alpha phase the majority of precipitates appears to be platelets or rods with the habit plane being parallel to (1010) of the matrix. As the precipitates exceeded a critical size of approximately 5000 A, dislocations were observed to be emitted from the interface into the matrix. The beta to alpha phase transformation produced a high density of dislocations which was caused by heterogeneous shear associated with the transformation. These dislocations acted as the preferential nucleation sites for the precipitates. (Author)

Descriptors :   (*TITANIUM ALLOYS, ELECTRON MICROSCOPY), (*COPPER ALLOYS, CRYSTAL DEFECTS), CRYOGENICS, DEFORMATION, NUCLEATION, PHASE STUDIES, CRYSTAL STRUCTURE, SHEAR STRESSES, QUENCHING, SYMMETRY(CRYSTALLOGRAPHY).

Subject Categories : Properties of Metals and Alloys
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE