抄録
The precipitation and growth of sigma phase in duplex stainless steel was investigated to clarify the quantitative effects of temperature and chemistry on growth rate in isothermal heating process. Intermetallic phase such as sigma phase is harmful for mechanical properties of duplex stainless steels. The increasing of alloying elements of Cr and Mo useful for improving of corrosion resistance promotes the sigma phase precipitation but that phase is not always formed rapidly. So it is meaningful to clarify the kinetics of precipitation to give the solution the trade off relation of high corrosion resistance and prevention of harmful phase precipitation.
A physical model of growth rate as function of temperature including the parameter regarding chemistries was suggested on the basis of traditional nucleation theory. The measurement of sigma phase conducted experimentally after heated at various temperature, employing 25%Cr duplex stainless steel containing various level of molybdenum, tungsten and nickel contents. Referring those data obtained, it was confirmed that the effects of temperature and molybdenum, tungsten and nickel contents on the growth rate is explained by the physical model suggested in this work.
