An experimental investigation of serrated flow in an aluminium-magnesium-silicon alloy

Abstract

A method involving photoclastic coatings, that depicts local changes in strain in the gage length of specimens by changes in color, was used. The strain behavior associated with different types of serrations was studied and recorded in a movie. It was confirmed that Type A serrations do indeed correspond to the formation of deformation bands at one end of the specimens and their propagation to the other end. Secondary serrations were observed during these serrations, and were found to correspond to localized strain in the specimens during the early stages of deformation. Type B serrations were identified with the formation of bands that do not propagate; these can form at random in the specimen, in the same region where other bands nucleated before, or successively ahead of each other. A decrease in the spring constant of the testing machine makes these bands propagate very fast over small distances, after their formation.