Effect of retained austenite and high temperature Laves phase on the work hardening of an experimental maraging steel

Maraging steels including the experimental alloy studied here show atypical stress-strain behaviour during tensile testing. In particular, there is a gradual decrease in the ability of the sample to support a stress following a small fraction of the total plastic strain to failure. It is demonstrated here that this phenomenon is not associated with the early onset of a necking instability, and that a large amount of the plastic strain beyond the peak stress is uniform. Investigations of microstructure and retained austenite content reveal that the intrinsic microstructure of maraging steels has a poor ability to work harden. The work hardening capacity can, as expected, be improved by introducing retained austenite, but there is an associated reduction in strength. Experiments have been designed to control the retained austenite content in such a way that clear comparisons can be made and conclusions reached on both the role of the austenite and of Laves phase generated at different temperatures.