Papers by Author: W.J. Liu

Abstract: Stress-relaxation method was first used by Liu and Jonas in 1980s for following the kinetics of strain induced precipitation of carbonitrides in austenite. Since then, the method has been widely employed for studying not only the precipitation kinetics but also the recovery and recrystallization processes in steels and other alloys. In the present paper, the principle and the worldwide usage of the method were reviewed. The dependence of stress relaxation rate on the occurrence of precipitation, recovery and recrystallization was interpreted based on a dislocation model. The capabilities and the limitations of the method were discussed and ways to overcome the existing limitations were also proposed.

Abstract: A model, which can be used to illustrate the process of nucleation of hydrogen induced cracking (HIC) in steels during sour service, was developed with the aid of Gibbs theory. A set of criteria for crack nucleation were then derived from the model. Metallurgical parameters influencing the criteria and thusly the susceptibility of the material to HIC, which are measurable and controllable in industrial processing, were also advanced in the present article.