Accession Number : ADA137378

Title :   Quasi-Cleavage and Martensite Habit Plane.

Descriptive Note : Technical rept.,

Corporate Author : LEHIGH UNIV BETHLEHEM PA INST OF FRACTURE AND SOLID MECHANICS

Personal Author(s) : Gao,M ; Wei,R P

PDF Url : ADA137378

Report Date : Sep 1983

Pagination or Media Count : 42

Abstract : Quasi-cleavage (QC) is often observed on the fracture surfaces of hydrogen embrittled iron and steels. For quenched-and-tempered martensitic high strength steels, most QC facets show geometrical markings that are made up of fine oblong elements arrayed at well defined angles. To better understand this mode of failure, scanning and transmission electron microscopy (SEM and TEM) and etch-pit analysis have been applied to the study of quasi-coverage and of martensitic structure in an AISI 4340 steel (tempered at 478 K). A special technique was developed for determining martensite habit planes without the need for concomitant presence of retained austenite or annealing twins in the microstructure. Quasi-cleavage in this AISI 4340 steel has been shown to be cleavage along (110) alpha, planes through martensites, and (225) gamma have been unambiguously determined as the martensite habit planes. The methods of analyses are described. The relationship between surface features of QC facets and the martensitic microstructure and the possible interaction between hydrogen and slip are discussed. Potential application of the analysis method to studies of martensitic transformation is considered. (Author)

Descriptors :   *Steel, *Martensite, *Hydrogen embrittlement, *Cracking(Fracturing), *Fracture(Mechanics), *Cleavage, Microstructure, Failure(Mechanics), Strength(Mechanics), Single crystals, Crystallography, Structural properties, Phase transformations, Fractography, Electron microscopy, Numerical analysis, Matrices(Mathematics), Tables(Data)

Subject Categories : Properties of Metals and Alloys
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE