KINETICS OF DECOMPOSITION OF RETAINED AUSTENITE DURING TEMPERING IN SOME HIGH STRENGTH STEELS
SHIH CHANG-HSU Institute of Metal Research;Academia Sinica
Cite this article:
SHIH CHANG-HSU Institute of Metal Research;Academia Sinica. KINETICS OF DECOMPOSITION OF RETAINED AUSTENITE DURING TEMPERING IN SOME HIGH STRENGTH STEELS. Acta Metall Sin, 1956, 1(4): 383-393.
Abstract The kinetics of decomposition of retained austenite in AISI 4325,AISI 4340and their silicon modified steels has been studied by precision length measurement.It is found that the internal stresses play a very important role in the first instantof transformation.In steels with normal silicon content(0.2—0.3%),the activation energy of thedecomposition of retained austenite is about 35,000 cal/mole,comparable to thatrequired for the diffusion of carbon in γ-Fe.In general,high silicon content(1.5% Si)retards the transformation of retain-ed austenite in these steels.Based upon the isothermal transformation curvesand rate equation the activation energy for this transformation has been deter-mined to be about 44,000 cal/mole,and it is therefore suggested that the diffusionof silicon in γ-Fe surrounding the growing carbide particles is possibly the ratecontrolling factor.