β Scribed by Gao Ming; R.P. Wei
No coin nor oath required. For personal study only.
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&avage and of martensitic structure in an AISI4340 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 { IIO), planes through martensites, and {225} have been unambiguously determined as the martensite habit planes. 7%~ methods of analyses are dwcribad. 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.
π SIMILAR VOLUMES
The phenomenological theory of martensite formation developed by Wechsler et al. has been used to predict the indices of plane interfaces formed during annealing between grams of a-and /?-brass, as well as the habit plane of precipitation of Fe,N, and Fe,P, from a-iron. The implications resulting fr