Edge Regularization Research Articles

Hydrogen‐ion image features of tempered martensite

SUMMARYHydrogen‐ion microscopy has been used to study first and third stage tempered ferrous martensite. Both ε‐carbide and cementite particles resulting from the tempering process appeared dark in the images. The image characteristics of the matrix phases in these specimens were intermediate between those of pure iron and as‐quenched ferrous martensite. The sharpness of the (111) zone lines and the ‘butterfly’ pattern in {110} regions, the development of high index planes and the regularity of low index net plane edges decreased continuously with increasing carbon content of the matrix phase. The effects of carbon content and lattice strain on specimen geometry, field evaporation, hydrogen etching and field ionization are discussed. It is suggested that carbon atoms in random solid solution lead to an irregular evaporation, similar to that previously proposed for other solid solution alloys, and that the irregular evaporation is enhanced by the associated lattice strain and hydrogen etching process. The irregular end form thus produced lacks the sharp image features found in the smoother end form of the pure metal.

Field-ion microscopy of ferrous martensite

Abstract Fine structures of as-quenched martensite in an Fe-0.8% C-0.4% Mn steel were investigated using field-ion microscopy techniques. Both untwinned and twinned martensite regions were detected. Differences in image contrast and regularity of net plane edges were found in the hydrogen-ion images of pure iron and untwinned martensite. It is proposed that in the twinned martensite images the twins appear as bright bands while dark bands represent the intersection of twin boundaries with the specimen surface. The twins were found to have a {112} orientation and a width of 25–100 A.